@article{wise_curry_harmon_2024, title={Reevaluation of the K/Rb-Li Systematics in Muscovite as a Potential Exploration Tool for Identifying Li Mineralization in Granitic Pegmatites}, volume={14}, ISSN={["2075-163X"]}, DOI={10.3390/min14010117}, abstractNote={A dataset of >1190 published compositional analyses of muscovite from granitic pegmatites of varying mineralogical types was compiled to reevaluate the usefulness of K-Rb-Li systematics of muscovite as a tool for distinguishing mineralogically simple pegmatites from pegmatites with potential Li mineralization. Muscovite from (i) common, (ii) (Be-Nb-Ta-P)-enriched, (iii) Li-enriched, and (iv) REE- to F-enriched pegmatites contain Li contents that vary between 10 and 20,000 ppm depending on the degree of pegmatite fractionation. Common pegmatites are characterized by low degrees of fractionation as exhibited by K/Rb ratios ranging from 618 and 25 and Li contents generally being <200 ppm but infrequently as high as 743 ppm in muscovite. Moderately fractionated pegmatites with Be, Nb, Ta, and P enrichment contain muscovite having K/Rb ratios mostly between 45 and 7 plus Li contents between 5 to >1700 ppm. Muscovite from moderately to highly fractionated Li-rich pegmatites exhibit a wide range of K/Rb ratios and Li values: (i) K/Rb = 84 to 1.4 and Li = 35 to >18,100 ppm for spodumene pegmatites, (ii) K/Rb = 139 to 2 and Li = 139 to >18,500 ppm for petalite pegmatites, and (iii) K/Rb = 55 to 1.5 and Li = 743 to >17,800 ppm for lepidolite pegmatites. Pegmatites that host substantial REE- and F-rich minerals may carry muscovite with K/Rb ratios between 691 to 4 that has Li contents between 19 to 15,690 ppm. The K/Rb-Li behavior of muscovite can be useful in assessing the potential for Li mineralization in certain granitic pegmatite types. The proposed limits of K/Rb values and Li concentrations for identifying spodumene- or petalite-bearing pegmatites as part of an exploration program is reliable for Group 1 (LCT) pegmatite populations derived from S-type parental granites or anatectic melting of peraluminous metasedimentary rocks. However, it is not recommended for application to Group 2 (NYF) pegmatites affiliated with anorogenic to post-orogenic granitoids with A-type geochemical signatures or that derived by the anatexis of mafic rocks that generated REE- and F-rich melts.}, number={1}, journal={MINERALS}, author={Wise, Michael A. and Curry, Adam C. and Harmon, Russell S.}, year={2024}, month={Jan} }
 @article{harmon_throckmorton_haverstock_baron_yohe_hark_knott_2023, title={Connecting Obsidian Artifacts with Their Sources Using Multivariate Statistical Analysis of LIBS Spectral Signatures}, volume={13}, ISSN={["2075-163X"]}, DOI={10.3390/min13101284}, abstractNote={With the recent introduction of handheld instruments for field use, laser-induced breakdown spectroscopy (LIBS) is emerging as a practical technology for real-time in situ geochemical analysis in the field. LIBS is a form of optical emission spectroscopy that is simultaneously sensitive to all elements with a single laser shot so that a broadband LIBS spectrum can be considered a diagnostic geochemical fingerprint. Sets of LIBS spectra were collected for seven obsidian centers across north-central California, with data processed using multivariate statistical analysis and pattern recognition techniques. Although all obsidians exhibit similar bulk compositions, different regional obsidian sources were effectively discriminated via partial least squares discriminant analysis. Obsidian artifacts from seven archaeological sites were matched to their putative sources with a high degree of confidence.}, number={10}, journal={MINERALS}, author={Harmon, Russell S. and Throckmorton, Chandra S. and Haverstock, Greg and Baron, Dirk and Yohe, Robert M. and Hark, Richard R. and Knott, Jeffrey R.}, year={2023}, month={Oct} }
 @article{hoefs_harmon_2023, title={Isotopic history of seawater: the stable isotope character of the global ocean at present and in the geological past}, ISSN={["1477-2639"]}, DOI={10.1080/10256016.2023.2271127}, abstractNote={ABSTRACT After the atmosphere, the ocean is the most well-mixed and homogeneous global geochemical reservoir. Both physical and biological processes generate elemental and isotope variations in seawater. Contrasting geochemical behaviors cause elements to be susceptible to different fractionation mechanisms, with their isotopes providing unique insights into the composition and evolution of the ocean over the course of geological history. Supplementing the traditional stable isotopes (H, C, O, N, S) that provide information about ocean processes and past environmental conditions, radiogenic isotope (Sr, Nd, Os, Pb, U) systems can be used as time markers, indicators of terrestrial weathering, and ocean water mass mixing. Recent instrumentation advances have made possible the measurement of natural stable isotope variations produced by both mass-dependent and mass-independent fractionation for an ever-increasing number of metal elements (e.g. Li, B, Mg, Si, Ca, V, Cr, Fe, Ni, Cu, Zn, Se, Mo, Cd, Tl, U). The major emphasis in this review is on the isotopic composition of the light elements based on a comparatively large literature. Unlike O, H and S, the stable isotopes of C, N and Si do not have a constant isotopic composition in the modern ocean. The major cations Ca, Mg, and Sr fixed in carbonate shells provide the best proxies for reconstruction of the composition of the ocean in the past. Exhibiting large isotope enrichments in ocean water, B and Li are suitable for the investigation of water/rock interactions and can act as monitors of former oceanic pH. The bioessential elements Zn, Cd, and Ni are indicators of paleoproductivity in the ocean. Characteristic isotope enrichments or depletions of the multivalent elements V, Cr, Fe, Se, Mo, and U record the past redox state of the ocean/atmosphere system. Case studies describe how isotopes have been used to define the seawater composition in the geological past.}, journal={ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES}, author={Hoefs, Jochen and Harmon, Russell S.}, year={2023}, month={Oct} }
 @article{harmon_wise_curry_mistele_mason_grimac_2023, title={Rapid Analysis of Muscovites on a Lithium Pegmatite Prospect by Handheld LIBS}, volume={13}, ISSN={["2075-163X"]}, DOI={10.3390/min13050697}, abstractNote={Laser-induced breakdown spectroscopy (LIBS) is a technology for compositional analysis that is particularly effective for light elements, particularly Li, which is a critical commodity for emerging green technologies. This study undertook analysis by handheld LIBS of muscovite from the drill core, outcrop, and soil on the Carolina Lithium Prospect (CLP) in Gaston County, North Carolina (USA), which lies within the Carolina Tin-Spodumene Belt (CTSB). Abundances of the alkali elements Li, K, and Rb were determined for more than 130 muscovites from the Li-rich pegmatites to track the degree of pegmatite fractionation as a pathfinder for spodumene mineralization. Across the CTSB and including the CLP, muscovite Li contents vary over an order of magnitude, ranging from 0.04 to 0.74 wt. %, with their K/Rb ratios varying between 63 and 8, features that together document the highly evolved character of pegmatites within the CTSB district. On average, muscovite Li contents are greater in spodumene-bearing pegmatites at 0.21 ± 0.12 wt. % than for common quartz-feldspar pegmatites at 0.14 ± 0.08 wt. %. Although overlapping substantially in the middle portions of their distributions, muscovite K/Rb ratios are biased toward low values for spodumene-bearing pegmatites (X- = 21 ± 6) compared to those for quartz-feldspar pegmatites (X- = 33 ± 9). This study provides a framework for the use of LIBS analysis of muscovite in outcrop, drill core, and soil samples as an analytical tool for in-field and on-site geochemical analysis during Li pegmatite exploration and prospect evaluation.}, number={5}, journal={MINERALS}, author={Harmon, Russell S. and Wise, Michael A. and Curry, Adam C. and Mistele, Joshua S. and Mason, Michael S. and Grimac, Zach}, year={2023}, month={May} }
 @article{pappala_arendt_harmon_2023, title={Spatial characterization of chemical weathering in a proglacial river system, southcentral Alaska}, volume={629}, ISSN={["1872-6836"]}, DOI={10.1016/j.chemgeo.2023.121462}, abstractNote={Major constituent concentrations (Na+, K+, Ca2+, Mg2+, HCO3−, SO42−, Cl−, NO3−) were determined for a 121 km reach of the proglacial Matanuska River, associated tributaries, and five additional glacial rivers on the Kenai Peninsula of southcentral Alaska during peak flow conditions in July 2019. Mass balance and mixing models were utilized to gain insight to chemical weathering processes and carbon feedback implications along the sampling transect. Solute compositions of the Matanuska River varied spatially, shifting from carbonate dominance near the terminus of the Matanuska Glacier to a carbonate-silicate weathering signature in the lower reaches of the river. Geochemical modeling suggests that carbonate dissolution closest to the Matanuska Glacier terminus is driven by sulfuric acid produced from the oxidation of sulfide minerals in the subglacial and proglacial system that acts as a source of CO2. This contrasts with the lower reaches of the Matanuska River, its tributaries, and other Kenai glacial rivers, where mineral dissolution is dominated by carbonic acid and weathering acts as a sink of atmospheric CO2. The spatial variations observed in stream and river compositions are predominantly attributed to the local lithological variations across the catchment, with subglacial weathering signatures observed in the meltwater solute compositions closest to the Matanuska Glacier terminus. This study highlights the importance of spatial sampling in proglacial systems, as proglacial water chemical signatures and carbon feedback implications can shift significantly away from the glacial terminus.}, journal={CHEMICAL GEOLOGY}, author={Pappala, Venkata Sailaja and Arendt, Carli A. and Harmon, Russell S.}, year={2023}, month={Jul} }
 @article{kempton_mathur_harmon_bell_hoefs_shaulis_2022, title={Cu-Isotope Evidence for Subduction Modification of Lithospheric Mantle}, volume={23}, ISSN={["1525-2027"]}, DOI={10.1029/2022GC010436}, abstractNote={Abstract}, number={8}, journal={GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS}, author={Kempton, Pamela D. and Mathur, Ryan and Harmon, Russell S. and Bell, Aaron and Hoefs, Jochen and Shaulis, Barry}, year={2022}, month={Aug} }
 @article{wise_harmon_curry_jennings_grimac_khashchevskaya_2022, title={Handheld LIBS for Li Exploration: An Example from the Carolina Tin-Spodumene Belt, USA}, volume={12}, ISSN={["2075-163X"]}, DOI={10.3390/min12010077}, abstractNote={Laser-induced breakdown spectroscopy (LIBS), which has recently emerged as tool for geochemical analysis outside the traditional laboratory setting, is an ideal tool for Li exploration because it is the only technique that can measure Li in minerals, rocks, soils, and brines in-situ in the field. In addition to being used in many products essential to modern life, Li is a necessary element for a reduced carbon future and Li–Cs–Ta (LCT) granitic pegmatites are an important source of Li. Such pegmatites can have varying degrees of enrichment in Li, Rb, Cs, Be, Sn, Ga, Ta>Nb, B, P, and F. We focus here on the LCT pegmatites of the Carolina Tin-Spodumene Belt (CTSB) situated in the Kings Mountain Shear Zone, which extends from South Carolina into North Carolina. The CTSB hosts both barren and fertile pegmatites, with Li-enriched pegmatites containing spodumene, K-feldspar, albite, quartz, muscovite, and beryl. We illustrate how handheld LIBS analysis can be used for real-time Li analysis in the field at a historically important CTSB pegmatite locality in Gaston County, N.C. in four contexts: (i) elemental detection and identification; (ii) microchemical mapping; (iii) depth profiling; and (iv) elemental quantitative analysis. Finally, as an example of a practical exploration application, we describe how handheld LIBS can be used to measure K/Rb ratios and Li contents of muscovite and rapidly determine the degree of pegmatite fractionation. This study demonstrates the potential of handheld LIBS to drastically reduce the time necessary to acquire geochemical data relevant to acquiring compositional information for pegmatites during a Li pegmatite exploration program.}, number={1}, journal={MINERALS}, author={Wise, Michael A. and Harmon, Russell S. and Curry, Adam and Jennings, Morgan and Grimac, Zach and Khashchevskaya, Daria}, year={2022}, month={Jan} }
 @misc{hoefs_harmon_2022, title={The Earth's atmosphere - A stable isotope perspective and review}, volume={143}, ISSN={["1872-9134"]}, DOI={10.1016/j.apgeochem.2022.105355}, abstractNote={This review summarizes the stable isotope composition of the gases and aerosols comprising the Earth's atmosphere. Recent technical progress in analytical methodologies has enabled analysis the H- and O-isotopic composition of water vapor by remote sensing, precise measurement of the rare isotopes 17O, 33S and 36S, the recognition of mass-independent isotope fractionations, and determination of the stable isotope composition of volatile metals in aerosols. Together these approaches have resulted in new insights into atmospheric processes and permitted the delineation of atmospheric constituents derived from natural versus anthropogenic sources. Ice core analysis has demonstrated that the isotope composition of the atmosphere has changed continuously as a consequence of both past climate cycles and more recently because of fossil fuel and other anthropogenic emissions. Isotope proxies and geochemical modeling have recognized that the nature of the atmosphere has varied throughout geologic history and will continue to do so in the near future.}, journal={APPLIED GEOCHEMISTRY}, author={Hoefs, Jochen and Harmon, Russell}, year={2022}, month={Aug} }
 @article{defnet_wise_harmon_hark_hilferding_2021, title={Analysis of Garnet by Laser-Induced Breakdown Spectroscopy-Two Practical Applications}, volume={11}, ISSN={["2075-163X"]}, DOI={10.3390/min11070705}, abstractNote={Laser-induced breakdown spectroscopy (LIBS) is a simple and straightforward technique of atomic emission spectroscopy that can provide multi-element detection and quantification in any material, in-situ and in real time because all elements emit in the 200–900 nm spectral range of the LIBS optical emission. This study evaluated two practical applications of LIBS—validation of labels assigned to garnets in museum collections and discrimination of LCT (lithium-cesium-tantalum) and NYF (niobium, yttrium and fluorine) pegmatites based on garnet geochemical fingerprinting, both of which could be implemented on site in a museum or field setting with a handheld LIBS analyzer. Major element compositions were determined using electron microprobe analysis for a suite of 208 garnets from 24 countries to determine garnet type. Both commercial laboratory and handheld analyzers were then used to acquire LIBS broadband spectra that were chemometrically processed by partial least squares discriminant analysis (PLSDA) and linear support vector machine classification (SVM). High attribution success rates (>98%) were obtained using PLSDA and SVM for the handheld data suggesting that LIBS could be used in a museum setting to assign garnet type quickly and accurately. LIBS also identifies changes in garnet composition associated with increasing mineral and chemical complexity of LCT and NYF pegmatites.}, number={7}, journal={MINERALS}, author={Defnet, Peter A. and Wise, Michael A. and Harmon, Russell S. and Hark, Richard R. and Hilferding, Keith}, year={2021}, month={Jul} }
 @article{harmon_khashchevskaya_morency_owen_jennings_knott_dortch_2021, title={Analysis of Rock Varnish from the Mojave Desert by Handheld Laser-Induced Breakdown Spectroscopy}, volume={26}, ISSN={["1420-3049"]}, DOI={10.3390/molecules26175200}, abstractNote={Laser-induced breakdown spectroscopy (LIBS) is a form of optical emission spectroscopy that can be used for the rapid analysis of geological materials in the field under ambient environmental conditions. We describe here the innovative use of handheld LIBS for the in situ analysis of rock varnish. This thinly laminated and compositionally complex veneer forms slowly over time on rock surfaces in dryland regions and is particularly abundant across the Mojave Desert climatic region of east-central California (USA). Following the depth profiling examination of a varnished clast from colluvial gravel in Death Valley in the laboratory, our in situ analysis of rock varnish and visually similar coatings on rock surfaces was undertaken in the Owens and Deep Spring valleys in two contexts, element detection/identification and microchemical mapping. Emission peaks were recognized in the LIBS spectra for the nine elements most abundant in rock varnish—Mn, Fe, Si, Al, Na, Mg, K, Ca and Ba, as well as for H, Li, C, O, Ti, V, Sr and Rb. Focused follow-up laboratory and field studies will help understand rock varnish formation and its utility for weathering and chronological studies.}, number={17}, journal={MOLECULES}, author={Harmon, Russell S. and Khashchevskaya, Daria and Morency, Michelle and Owen, Lewis A. and Jennings, Morgan and Knott, Jeffrey R. and Dortch, Jason M.}, year={2021}, month={Sep} }
 @misc{senesi_harmon_hark_2021, title={Field-portable and handheld laser-induced breakdown spectroscopy: Historical review, current status and future prospects}, volume={175}, ISSN={["1873-3565"]}, DOI={10.1016/j.sab.2020.106013}, abstractNote={The first part of this review describes laser-induced breakdown spectroscopy (LIBS) instrumentation for in situ measurement outside the laboratory, both prototype instruments and commercially available analyzers that can be operated by a single individual. Two types of devices are described – (i) field-portable type systems consisting of multiple units connected by an umbilical (fpLIBS) and (ii) handheld analyzers (hLIBS). The performance of these two types of LIBS systems is compared with that of its primary competitor technology portable X-ray fluorescence spectroscopy (pXRF). The second part of the article reviews the results of both fpLIBS and hLIBS obtained in both research settings and for practical applications in various sectors where speed of analysis is often crucial. These include compositional screening of natural and manufactured materials, quality control of manufacturing processes, identification of environmental contaminants, biomedical diagnostics, forensic analysis, and hazardous material identification in the industrial, environmental, geological, cultural heritage, agricultural, biological, nuclear and security sectors. The review concludes by highlighting the key trends and challenging future directions in making LIBS technology readily accessible for applications that demand easy portability and fast analysis outside of the laboratory with instruments of compact dimensions and low weight but high performance, crucial features required for any portable device.}, journal={SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY}, author={Senesi, Giorgio S. and Harmon, Russell S. and Hark, Richard R.}, year={2021}, month={Jan} }
 @article{harmon_leslie_lyons_welch_mcknight_2021, title={Geochemistry of contrasting stream types, Taylor Valley, Antarctica}, volume={133}, ISSN={["1943-2674"]}, DOI={10.1130/B35479.1}, abstractNote={Abstract}, number={1-2}, journal={GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, author={Harmon, Russell S. and Leslie, Deborah L. and Lyons, W. Berry and Welch, Kathleen A. and McKnight, Diane M.}, year={2021}, pages={425–448} }
 @misc{harmon_senesi_2021, title={Laser-Induced Breakdown Spectroscopy - A geochemical tool for the 21st century}, volume={128}, ISSN={["1872-9134"]}, DOI={10.1016/j.apgeochem.2021.104929}, abstractNote={Laser-induced breakdown spectroscopy (LIBS) is a simple, straightforward, and versatile form of atomic emission spectroscopy that focuses a rapidly-pulsed laser beam onto a sample to form a plasma containing its constituent elements and then uses spectral analysis of the emitted light to detect the elements present. In theory, LIBS is capable of qualitative, semi-quantitative, and quantitative analysis of all elements in the periodic table. LIBS can be performed in the laboratory or outside in the ambient environment for on-site analysis in situ; LIBS can also be used for rapid microscale compositional imaging. This review first presents a description of the LIBS technique and then discusses and illustrates through a historic literature review how LIBS has been used to analyze gases, natural waters, minerals, rocks, sediments, and soils. Given the persistent need of analytical instrumentation for the rapid chemical analysis of geologic materials in the field, and the capability of LIBS to analyze any type of sample in real time with little to no preparation, there is a vast potential for the routine application of LIBS across a broad spectrum of the geosciences that is as yet only minimally realized.}, journal={APPLIED GEOCHEMISTRY}, author={Harmon, Russell S. and Senesi, Giorgio S.}, year={2021}, month={May} }
 @article{hark_throckmorton_harmon_plumer_harmon_harrison_hendrickx_clausen_2020, title={Multianalyzer Spectroscopic Data Fusion for Soil Characterization}, volume={10}, ISSN={["2076-3417"]}, DOI={10.3390/app10238723}, abstractNote={The ability to rapidly conduct in-situ chemical analysis of multiple samples of soil and other geological materials in the field offers many advantages over a traditional approach that involves collecting samples for subsequent examination in the laboratory. This study explores the application of complementary spectroscopic analyzers and a data fusion methodology for the classification/discrimination of >100 soil samples from sites across the United States. Commercially available, handheld analyzers for X-ray fluorescence spectroscopy (XRFS), Raman spectroscopy (RS), and laser-induced breakdown spectroscopy (LIBS) were used to collect data both in the laboratory and in the field. Following a common data pre-processing protocol, principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA) were used to build classification models. The features generated by PLSDA were then used in a hierarchical classification approach to assess the relative advantage of information fusion, which increased classification accuracy over any of the individual sensors from 80-91% to 94% and 64-93% to 98% for the two largest sample suites. The results show that additional testing with data sets for which classification with individual analyzers is modest might provide greater insight into the limits of data fusion for improving classification accuracy.}, number={23}, journal={APPLIED SCIENCES-BASEL}, author={Hark, Richard R. and Throckmorton, Chandra S. and Harmon, Russell S. and Plumer, John R. and Harmon, Karen A. and Harrison, J. Bruce and Hendrickx, Jan M. H. and Clausen, Jay L.}, year={2020}, month={Dec} }
 @article{smith_goldsmith_harmon_espinosa_harmon_2020, title={Physical controls and ENSO event influence on weathering in the Panama Canal Watershed}, volume={10}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-020-67797-7}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Smith, Devin F. and Goldsmith, Steven T. and Harmon, Brendan A. and Espinosa, Jorge A. and Harmon, Russell S.}, year={2020}, month={Jul} }
 @article{starek_chu_mitasova_harmon_2020, title={Viewshed simulation and optimization for digital terrain modelling with terrestrial laser scanning}, volume={41}, ISSN={["1366-5901"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85087281550&partnerID=MN8TOARS}, DOI={10.1080/01431161.2020.1752952}, abstractNote={ABSTRACT The main objective of this study is the development of a simulation and optimization method for wide-area terrain mapping with terrestrial laser scanning (TLS). The problem can be stated as follows: given a prior digital surface model (DSM) of a region of interest (e.g. from airborne lidar or structure-from-motion photogrammetry), determine the minimum number of scan locations required to seamlessly scan the terrain in the region for a given scanner range and angular field-of-view (FOV). An optimization method for measurement setup is developed using multiple viewshed analysis and simulated annealing (SA) constrained by the system performance characteristics and survey specifications. The method is evaluated at a sediment and erosion control facility with hilly terrain by comparing random scan locations versus optimized three to six scan locations. Statistical results illustrate that average visibility for random sampling increases gradually with scan locations. However, random sampling clearly underperforms in terms of scan visibility relative to five or six optimized scan locations with an average visibility of 100%. Similar patterns in optimized scan locations demonstrate that certain terrain morphometry at the study site is an essential factor for TLS survey design. Finally, an optimized solution is compared to a brute-force manual solution for determining four scan locations for conducting surveys at the study site. Results show the effectiveness of the optimization method for selecting combinations of scan locations that enable more efficient TLS survey coverage over a wider terrain area compared to manual selection. Furthermore, results demonstrate the adaptability of the method to take into consideration different scan parameters and survey conditions, such as pre-determined scan locations that may be required (e.g. a survey control monument).}, number={16}, journal={INTERNATIONAL JOURNAL OF REMOTE SENSING}, author={Starek, Michael J. and Chu, Tianxing and Mitasova, Helena and Harmon, Russell S.}, year={2020}, month={Aug}, pages={6409–6426} }
 @article{harmon_leslie_lyons_welch_mcknight_2019, title={Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica}, volume={98}, ISSN={["2267-1242"]}, DOI={10.1051/e3sconf/20199801020}, abstractNote={Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.}, journal={16TH INTERNATIONAL SYMPOSIUM ON WATER-ROCK INTERACTION (WRI-16) AND 13TH INTERNATIONAL SYMPOSIUM ON APPLIED ISOTOPE GEOCHEMISTRY (1ST IAGC INTERNATIONAL CONFERENCE)}, author={Harmon, Russell S. and Leslie, Deborah L. and Lyons, W. Berry and Welch, Kathleen A. and McKnight, Diane M.}, year={2019} }
 @article{harmon_lawley_watts_harraden_somers_hark_2019, title={Laser-Induced Breakdown Spectroscopy-An Emerging Analytical Tool for Mineral Exploration}, volume={9}, ISSN={["2075-163X"]}, DOI={10.3390/min9120718}, abstractNote={The mineral exploration industry requires new methods and tools to address the challenges of declining mineral reserves and increasing discovery costs. Laser-induced breakdown spectroscopy (LIBS) represents an emerging geochemical tool for mineral exploration that can provide rapid, in situ, compositional analysis and high-resolution imaging in both laboratory and field and settings. We demonstrate through a review of previously published research and our new results how LIBS can be applied to qualitative element detection for geochemical fingerprinting, sample classification, and discrimination, as well as quantitative geochemical analysis, rock characterization by grain size analysis, and in situ geochemical imaging. LIBS can detect elements with low atomic number (i.e., light elements), some of which are important pathfinder elements for mineral exploration and/or are classified as critical commodities for emerging green technologies. LIBS data can be acquired in situ, facilitating the interpretation of geochemical data in a mineralogical context, which is important for unraveling the complex geological history of most ore systems. LIBS technology is available as a handheld analyzer, thus providing a field capability to acquire low-cost geochemical analyses in real time. As a consequence, LIBS has wide potential to be utilized in mineral exploration, prospect evaluation, and deposit exploitation quality control. LIBS is ideally suited for field exploration programs that would benefit from rapid chemical analysis under ambient environmental conditions.}, number={12}, journal={MINERALS}, author={Harmon, Russell S. and Lawley, Christopher J. M. and Watts, Jordan and Harraden, Cassady L. and Somers, Andrew M. and Hark, Richard R.}, year={2019}, month={Dec} }
 @article{shouakar-stash_kharaka_koopmann_harmon_negrel_wanty_2018, title={A remembrance of Thomas (Tom) Bullen, 1951-2018}, volume={98}, ISSN={["0883-2927"]}, DOI={10.1016/j.apgeochem.2018.10.004}, journal={APPLIED GEOCHEMISTRY}, author={Shouakar-Stash, Orfan and Kharaka, Yousif and Koopmann, Roger and Harmon, Russell and Negrel, Philippe and Wanty, Richard B.}, year={2018}, month={Nov}, pages={474–475} }
 @article{harmon_throckmorton_hark_gottfried_woerner_harpp_collins_2018, title={Discriminating volcanic centers with handheld laser-induced breakdown spectroscopy (LIBS)}, volume={98}, ISSN={["1095-9238"]}, DOI={10.1016/j.jas.2018.07.009}, abstractNote={Microcrystalline igneous rocks of volcanic origin, such as basalt or rhyolite, were a common source of prehistoric stone tools. This study explores the use of laser-induced breakdown spectroscopy (LIBS) as part of an effort to develop analytical tools to examine geological materials of archaeological interest. LIBS is a method of atomic emission spectroscopy capable of providing rapid, in situ elemental analysis of any material with minimal to no sample preparation. We have utilized both a bespoke laboratory system and a commercial handheld analyzer to acquire broadband LIBS emission spectra for fresh and unaltered volcanic samples of varying age and composition from two tectonic settings. The distinguishing chemical characteristics of the different volcanic regions and centers were identified and their sources differentiated through multivariate chemometric analysis. Classification and discrimination has been achieved with a high degree of success using a pattern recognition approach. These results suggest that the provenance of stone artifacts may be identified in the field using handheld LIBS through the use of algorithmic matching of LIBS emission spectra against a sufficiently robust and representative database previously prepared by analysis of samples of known origin.}, journal={JOURNAL OF ARCHAEOLOGICAL SCIENCE}, author={Harmon, Russell S. and Throckmorton, Chandra S. and Hark, Richard R. and Gottfried, Jennifer L. and Woerner, Gerhard and Harpp, Karen and Collins, Leslie}, year={2018}, month={Oct}, pages={112–127} }
 @article{harmon_2018, title={Remembrance Melvyn (Mel) Gascoyne, 1948-2018 Obituary}, volume={98}, ISSN={["0883-2927"]}, DOI={10.1016/j.apgeochem.2018.08.018}, journal={APPLIED GEOCHEMISTRY}, author={Harmon, Russell}, year={2018}, month={Nov}, pages={473–473} }
 @article{harmon_hark_throckmorton_rankey_wise_somers_collins_2017, title={Geochemical Fingerprinting by Handheld Laser-Induced Breakdown Spectroscopy}, volume={41}, ISSN={["1751-908X"]}, DOI={10.1111/ggr.12175}, abstractNote={A broad suite of geological materials was studied a using a handheld laser‐induced breakdown spectroscopy (LIBS) instrument. Because LIBS is simultaneously sensitive to all elements, the full broadband emission spectrum recorded from a single laser shot provides a ‘chemical fingerprint’ of any material – solid, liquid or gas. The distinguishing chemical characteristics of the samples analysed were identified through principal component analysis (PCA), which demonstrates how this technique for statistical analysis can be used to identify spectral differences between similar sample types based on minor and trace constituents. Partial least squares discriminant analysis (PLSDA) was used to distinguish and classify the materials, with excellent discrimination achieved for all sample types. This study illustrates through four examples (carbonate minerals and rocks, the oxide mineral pair columbite–tantalite, the silicate mineral garnet and native gold) how portable, handheld LIBS analysers can be used for real‐time chemical analysis under simulated field conditions for element or mineral identification, plus such applications as stratigraphic correlation, provenance determination and natural resource exploration.}, number={4}, journal={GEOSTANDARDS AND GEOANALYTICAL RESEARCH}, author={Harmon, Russell S. and Hark, Richard R. and Throckmorton, Chandra S. and Rankey, Eugene C. and Wise, Michael A. and Somers, Andrew M. and Collins, Leslie M.}, year={2017}, month={Dec}, pages={563–584} }
 @article{harmon_woerner_goldsmith_harmon_gardner_lyons_ogden_pribil_long_kern_et al._2016, title={Linking silicate weathering to riverine geochemistry-A case study from a mountainous tropical setting in west-central Panama}, volume={128}, ISSN={["1943-2674"]}, DOI={10.1130/b31388.1}, abstractNote={Chemical analyses from 71 watersheds across an ∼450 km transect in west-central Panama provide insight into controls on weathering and rates of chemical denudation and CO2 consumption across an igneous arc terrain in the tropics. Stream and river compositions across this region of Panama are generally dilute, having a total dissolved solute value = 118 ± 91 mg/L, with bicarbonate and silica being the predominant dissolved species. Solute, stable isotope, and radiogenic isotope compositions are consistent with dissolution of igneous rocks present in Panama by meteoric precipitation, with geochemical signatures of rivers largely acquired in their upstream regions. Comparison of a headwater basin with its entire watershed observed considerably more runoff production from the high-elevation upstream portion of the catchment than in its much more spatially extensive downstream region. Rock alteration profiles document that weathering proceeds primarily by dissolution of feldspar and pyroxene, with base cations effectively leached in the following sequence: Na > Ca > Mg > K. Control on water chemistry by bedrock lithology is indicated through a linking of elevated ([Na + K]/[Ca + Mg]) ratios in waters to a high proportion of catchment area silicic bedrock and low ratios to mafic bedrock. Sr-isotope ratios are dominated by basement-derived Sr, with only very minor, if any, contribution from other sources. Cation weathering of Casil + Mgsil + Na + K spans about an order in magnitude, from 3 to 32 tons/km2/yr. Strong positive correlations of chemical denudation and CO2 consumption are observed with precipitation, mean watershed elevation, extent of land surface forest cover, and physical erosion rate.}, number={11-12}, journal={GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, author={Harmon, Russell S. and Woerner, Gerhard and Goldsmith, Steven T. and Harmon, Brendan A. and Gardner, Christopher B. and Lyons, W. Berry and Ogden, Fred L. and Pribil, Michael J. and Long, David T. and Kern, Zoltan and et al.}, year={2016}, month={Nov}, pages={1780–1812} }
 @article{kern_harmon_forizs_2016, title={Stable isotope signatures of seasonal precipitation on the Pacific coast of central Panama}, volume={52}, ISSN={["1477-2639"]}, DOI={10.1080/10256016.2015.1016021}, abstractNote={As calculated from data archived in the IAEA-WMO Global Network of Isotopes in Precipitation programme, the amount-weighted local meteoric water line for the Pacific coast of central Panama is: δ2H = 7.63(±0.08) × δ18O + 6.51(±0.49). Amount-weighted mean isotopic values were regressed against the sea surface temperature (SST) fields of the adjacent tropical oceans. A negative correlation of precipitation isotope composition with Caribbean SSTs is observed only for the early wet season (May–June), whilst the mid-summer dry period is characterized by positive correlation with eastern Pacific SSTs, similar to the late wet season (October–November). The negative response of May–June rainfall isotopic composition to Caribbean SSTs is explained by a SST-mediated change in stratiform rain fraction from organized convective systems proximal to the Inter Tropical Convergence Zone (ITCZ). The positive correlation for the rest of the wet season, when the organized convective zone of ITCZ and its attached stratiform belt are distant from the Pacific coast of Panama, is interpreted as simple evaporative temperature effect on isotopic fractionation.}, number={1-2}, journal={ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES}, author={Kern, Zoltan and Harmon, Russell S. and Forizs, Istvan}, year={2016}, month={Mar}, pages={128–140} }
 @article{goldsmith_harmon_lyons_harmon_ogden_gardner_2015, title={Evaluation of controls on silicate weathering in tropical mountainous rivers: Insights from the Isthmus of Panama}, volume={43}, DOI={10.1130/g36082.1}, abstractNote={The Isthmus of Panama comprises a lithologically diverse andesitic oceanic arc of Late Cretaceous to Holocene age; it has large spatial variation in rainfall, displays a large range of physical erosion rates, and, therefore, is an ideal location to examine silicate weathering in the tropics. We use a multiyear data set of river chemistry for a 450 km transect across the Cordillera Central of west-central Panama to investigate controls on chemical weathering in tropical small mountainous rivers. Sea-salt corrected cation weathering yields (Casil + Mgsil + Na + K) range over more than an order in magnitude from 3.1 to 31.7 t/km2/yr, while silicate weathering yields (Casil + Mgsil + Na + K + Si) range from 6.9 to 69.5 t/km2/yr. Watershed lithology is the primary control on riverine chemistry, but landscape topographic character and land cover and/or land use also influence solute delivery potential. Strong statistical links of small mountainous river chemical weathering fluxes with rainfall and physical weathering rates attest to the importance of runoff and erosion in maintaining elevated bedrock weathering rates. CO2 consumption ranges from 155 × 103 mol/km2/yr to 1566 × 103 mol/km2/yr, in the upper range of global rates, leading us to suggest that andesite terrains should be considered separately when calculating removal of CO2 from the atmosphere via silicate weathering.}, number={7}, journal={Geology (Boulder, Colo.)}, author={Goldsmith, S. T. and Harmon, R. S. and Lyons, W. B. and Harmon, B. A. and Ogden, F. L. and Gardner, C. B.}, year={2015}, pages={563–566} }
 @article{goldsmith_moyer_harmon_2015, title={Hydrochemistry and biogeochemistry of tropical small mountain rivers}, volume={63}, ISSN={["0883-2927"]}, DOI={10.1016/j.apgeochem.2015.11.005}, abstractNote={Small river basins represent an important source of dissolved nutrients to the coast, which are fundamental to coastal primary production. However, such transport is a resultant of nutrient fluxes from small rivers, estuarine modulation and, currently, anthropic emission loads. In this context, this study assessed ammonium (NH4+) and phosphate (PO43−) dynamics in a small subtropical river-estuary system by addressing seasonal fluxes from the river to the estuary, as well as the estuarine spring-neap tidal modulation, the resultant fluxes to the coast, and the influence of natural processes and anthropogenic activities on the land-sea nutrient dynamics. The results indicated that NH4+ and PO43− fluxes in the small river-estuary system were influenced by anthropic emission loads and by estuarine modulation through amplification of river discharge and NH4+ and PO43− concentrations and fluxes within the estuary. During most of the time, the small river-estuary system exported such dissolved nutrients to the coast, likely contributing to coastal primary production.}, journal={APPLIED GEOCHEMISTRY}, author={Goldsmith, Steven T. and Moyer, Ryan P. and Harmon, Russell J.}, year={2015}, month={Dec}, pages={453–455} }
 @article{harmon_woerner_pribil_kern_forizs_lyons_gardner_goldsmith_2015, title={Isotopic Geochemistry of Panama Rivers}, volume={13}, ISSN={["1878-5220"]}, DOI={10.1016/j.proeps.2015.07.026}, abstractNote={River water samples collected from 78 watersheds rivers along a 500-km transect across a Late Cretaceous-Tertiary andesitic volcanic arc terrane in west-central Panama provide a synoptic overview of riverine geochemistry, chemical denudation, and CO2 consumption in the tropics. D/H and 18O/16O relationships indicate that bedrock dissolution of andesitic arc crust in Panama is driven by water-rock interaction with meteoric precipitation as it passes through the critical zone, with no evidence of a geothermal or hydrothermal input. Sr-isotope relationships suggest a geochemical evolution for Panama riverine waters that involves mixing of bedrock pore water with water having 87Sr/86Sr ratios between 0.7037-0.7043 and relatively high Sr-contents with waters of low Sr content that enriched in radiogenic Sr that are diluted by infiltrating rainfall to variable extents.}, journal={11TH APPLIED ISOTOPE GEOCHEMISTRY CONFERENCE AIG-11}, author={Harmon, Russell S. and Woerner, Gerhard and Pribil, Michael J. and Kern, Zoltan and Forizs, Istvan and Lyons, W. Berry and Gardner, Christopher B. and Goldsmith, Steven T.}, year={2015}, pages={108–111} }
 @article{goldsmith_lyons_harmon_harmon_carey_mcelwee_2015, title={Organic carbon concentrations and transport in small mountain rivers, Panama}, volume={63}, ISSN={["1872-9134"]}, DOI={10.1016/j.apgeochem.2015.04.014}, abstractNote={Tropical small mountainous rivers (SMRs) are increasingly recognized for their role in the global export of dissolved organic carbon (DOC) to the oceans. Here we utilize the Isthmus of Panama as an ideal place to provide first-order estimates of DOC yields across a wide assemblage of bedrock lithologies and land cover practices. Samples for dissolved organic carbon (DOC) analysis were collected across Panama along an E–W transect from the central Panama area to the Costa Rican border for 24 mainstem rivers, 3 large tributary rivers, and one headwater stream. Sampling occurred during both the wet and the dry seasons. DOC concentrations during the wet season are higher than during the dry season in all but three of the rivers. Concentrations vary greatly from river to river and from season to season, with values as low as 0.64 mg l−1 to greater than >25 mg l−1 with the highest concentrations observed for the rivers draining Tertiary marine sedimentary rocks in the Burica and Azuero peninsulas. DOC yields from Panamanian rivers (2.29–7.97 tons/km2/y) are similar to or slightly lower than those determined for other tropical SMR systems. Areas underlain by Tertiary aged sediments exhibited significantly higher mean DOC yields compared to their igneous counterparts, despite maintaining substantially lower aboveground carbon densities, suggesting the important influence of lithology. Finally, regression analyses between DOC yields and select watershed parameters revealed a negative and statistically significant relationship with maximum and mean gradient suggesting lower soil retention times may be linked to lower DOC yields.}, journal={APPLIED GEOCHEMISTRY}, author={Goldsmith, Steven T. and Lyons, W. Berry and Harmon, Russell S. and Harmon, Brendan A. and Carey, Anne E. and McElwee, Gregg T.}, year={2015}, month={Dec}, pages={540–549} }
 @article{gilewitch_king_palka_harmon_mcdonald_doe_2014, title={Characterizing the desert environment for Army operations}, volume={22}, DOI={10.1130/2014.4122(07)}, abstractNote={Military geosciences are concerned with using the broad scope of the earth sciences for military purposes. These purposes range from direct support for military operations to a broad spectrum of non-combat military activities and military land management applications. Historically, the focus has been on geology and geography, but other earth science disciplines such as geophysics, remote sensing, and geocomputation have become increasingly important as a consequence of technological progress made during the final decades of the twentieth century. The eighteen chapters in this volume address the critical aspects of the role of geosciences in military undertakings by focusing on historical perspectives, geoscience for military operations, and military environmental stewardship.}, journal={Military geosciences in the twenty-first century}, author={Gilewitch, D. A. and King, W. C. and Palka, E. J. and Harmon, R. S. and McDonald, E. V. and Doe, W. W.}, year={2014}, pages={57–68} }
 @article{harmon_mcdonald_2014, title={Editors' introduction: Military geoscience in the twenty-first century-A historical perspective and overview}, volume={22}, DOI={10.1130/2014.4122(01)}, abstractNote={Military geosciences are concerned with using the broad scope of the earth sciences for military purposes. These purposes range from direct support for military operations to a broad spectrum of non-combat military activities and military land management applications. Historically, the focus has been on geology and geography, but other earth science disciplines such as geophysics, remote sensing, and geocomputation have become increasingly important as a consequence of technological progress made during the final decades of the twentieth century. The eighteen chapters in this volume address the critical aspects of the role of geosciences in military undertakings by focusing on historical perspectives, geoscience for military operations, and military environmental stewardship.}, journal={Military geosciences in the twenty-first century}, author={Harmon, R. S. and McDonald, E. V.}, year={2014}, pages={1–10} }
 @article{harmon_lyons_gardner_goldsmith_long_mitasova_welch_welch_2013, title={Surface water geochemistry and chemical weathering across Panama}, volume={7}, ISSN={["1878-5220"]}, DOI={10.1016/j.proeps.2013.03.134}, abstractNote={Abstract A geochemical study of rivers and streams was undertaken across Panama during 2005-09, from the Lago Bayano area in the east to the Costa Rican border in the west. Low overall dissolved solute contents (TDS = 145±160 mg/L) suggest a short residence time for infiltrating precipitation in the weathering zone. Watershed lithology exerts the main control on riverine chemistry, with streams on marine sedimentary rocks having higher dissolved solids loads than those on igneous rocks, with the latter exhibiting the highest silica contents and increasing trends of total cations with increasing dissolved silica. This feature and the large degree of compositional overlap between large rivers and small tributary streams implies that chemical weathering of silicate materials in the soil zone is the predominant process determining the geochemistry of streams and rivers in this tropical environment. Silicate weathering rates (Casil+Mgsil+Na+K) range over more than an order in magnitude from 2.5 to 28.4 tons/km2/y, whilst H4SiO4 yields range from 7.1 to 65 tons/km2/y. Basin-wide CO2 consumption yields by silicate weathering, calculated from total cation content (corrected for sea salt contribution), basin area and discharge, are high on a global basis.}, journal={PROCEEDINGS OF THE FOURTEENTH INTERNATIONAL SYMPOSIUM ON WATER-ROCK INTERACTION, WRI 14}, author={Harmon, Russell S. and Lyons, W. Berry and Gardner, Christopher B. and Goldsmith, Steven T. and Long, David T. and Mitasova, Helena and Welch, Susan and Welch, Kathy}, year={2013}, pages={342–345} }
 @article{lyons_leslie_harmon_neumann_welch_bisson_mcknight_2013, title={The carbon stable isotope biogeochemistry of streams, Taylor Valley, Antarctica}, volume={32}, ISSN={["1872-9134"]}, DOI={10.1016/j.apgeochem.2012.08.019}, abstractNote={The McMurdo Dry Valleys region of Antarctica is the largest ice-free region on the continent. This study reports the first C stable isotope measurements for dissolved inorganic C present in ephemeral streams in four dry valleys that flow for four to twelve weeks during the austral summer. One of these valleys, Taylor Valley, has been the focus of the McMurdo Dry Valleys Long-Term Ecological Research (MCM-LTER) program since 1993. Within Taylor Valley, numerous ephemeral streams deliver water to three perennially ice-covered, closed-basin lakes: Lake Fryxell, Lake Hoare, and Lake Bonney. The Onyx River in the Wright Valley, the longest river in Antarctica, flows for 40 km from the Wright Lower Glacier and Lake Brownworth at the foot of the glacier to Lake Vanda. Streamflow in the McMurdo Dry Valley streams is produced primarily from glacial melt, as there is no overland flow. However, hyporheic zone exchange can be a major hydrogeochemical process in these streams. Depending on landscape position, these streams vary in gradient, channel substrate, biomass abundance, and hyporheic zone extent. This study sampled streams from Taylor, Wright, Garwood, and Miers Valleys and conducted diurnal sampling of two streams of different character in Taylor Valley. In addition, transect sampling was undertaken of the Onyx River in Wright Valley. The δ13CPDB values from these streams span a range of greater than 14‰, from −9.4‰ to +5.1‰, with the majority of samples falling between −3‰ and +2‰, suggesting that the C stable isotope composition of dissolved C in McMurdo Dry Valley streams is largely inorganic in character. Because there are no vascular plants on this landscape and no groundwater input to these streams, atmospheric exchange is the dominant control on δ13C-DIC.}, journal={APPLIED GEOCHEMISTRY}, author={Lyons, W. B. and Leslie, D. L. and Harmon, R. S. and Neumann, K. and Welch, K. A. and Bisson, K. M. and McKnight, D. M.}, year={2013}, month={May}, pages={26–36} }
 @article{torres-alvarado_birkle_harmon_2012, title={13th International Symposium on Water-Rock Interaction (WRI-13) Preface}, volume={27}, ISSN={["0883-2927"]}, DOI={10.1016/j.apgeochem.2012.02.003}, abstractNote={The U234/238U ratio of fine particles can record the time since their separation from bed rock because of the disruption of uranium series equilibrium introduced by the recoil of daughter 234Th nuclei (precursor of 234U) out of particle surfaces during the decay of 238U. Application of the uranium comminution age method, which has great potential in tracing production and transportation of sediments is however complicated by the weathering dissolution of U234 depleted particle surfaces, the difficulty in determining the fraction of recoiled nuclei, and the precipitation of exogenetic U234. Here we minimize these complications by using a newly developed precise size separation using electroformed sieve, and a chemical protocol that involves reductive and oxidative leaching. Eolian deposits collected from the Chinese Loess Plateau (CLP) were used to test the validity of our method. Possible effects of weathering dissolution were also evaluated by comparing samples with different weathering intensities. The results show decreasing 234U/238U ratios in fine eolian particles with increasing sedimentation age, agreeing well with the theoretical prediction of the comminution age model. This successful application of the uranium comminution age approach to the eolian deposits on the CLP is also aided by a stable dust source, the low weathering intensity, the lack of consolidation, and the well-defined age model of the deposits. A transportation time of 242±18 ka was calculated for the eolian deposits, which indicates a long residence time, and thus extensive mixing, of the dust particles in source regions, partly explaining the stable and homogeneous composition of the eolian dust over glacial–interglacial cycles.}, number={9}, journal={APPLIED GEOCHEMISTRY}, author={Torres-Alvarado, Ignacio S. and Birkle, Peter and Harmon, Russell}, year={2012}, month={Sep}, pages={1679–1680} }
 @article{remus_harmon_hark_haverstock_baron_potter_bristol_east_2012, title={Advanced signal processing analysis of laser-induced breakdown spectroscopy data for the discrimination of obsidian sources}, volume={51}, ISSN={["2155-3165"]}, DOI={10.1364/ao.51.000b65}, abstractNote={Obsidian is a natural glass of volcanic origin and a primary resource used by indigenous peoples across North America for making tools. Geochemical studies of obsidian enhance understanding of artifact production and procurement and remain a priority activity within the archaeological community. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique being examined as a means for identifying obsidian from different sources on the basis of its 'geochemical fingerprint'. This study tested whether two major California obsidian centers could be distinguished from other obsidian localities and the extent to which subsources could be recognized within each of these centers. LIBS data sets were collected in two different spectral bands (350±130 nm and 690±115 nm) using a Nd:YAG 1064 nm laser operated at ~23 mJ, a Czerny-Turner spectrograph with 0.2-0.3 nm spectral resolution and a high performance imaging charge couple device (ICCD) detector. Classification of the samples was performed using partial least-squares discriminant analysis (PLSDA), a common chemometric technique for performing statistical regression on high-dimensional data. Discrimination of samples from the Coso Volcanic Field, Bodie Hills, and other major obsidian areas in north-central California was possible with an accuracy of greater than 90% using either spectral band.}, number={7}, journal={APPLIED OPTICS}, author={Remus, Jeremiah J. and Harmon, Russell S. and Hark, Richard R. and Haverstock, Gregory and Baron, Dirk and Potter, Ian K. and Bristol, Samantha K. and East, Lucille J.}, year={2012}, month={Mar}, pages={B65–B73} }
 @article{hark_remus_east_harmon_wise_tansi_shughrue_dunsin_liu_2012, title={Geographical analysis of "conflict minerals" utilizing laser-induced breakdown spectroscopy}, volume={74-75}, ISSN={["0584-8547"]}, DOI={10.1016/j.sab.2012.06.052}, abstractNote={Laser-induced breakdown spectroscopy (LIBS) offers a means of rapidly distinguishing different geographic sources for a mineral because the LIBS plasma emission spectrum provides information on the chemical composition (i.e. geochemical fingerprint) of a geomaterial. An application of this approach with potentially significant commercial and political importance is the spectral fingerprinting of “conflict minerals” such as columbite–tantalite (“coltan”). Following a successful pilot study of a columbite–tantalite suite from North America, a more geographically diverse set of 57 samples from 37 locations around the world was analyzed using a commercially available LIBS system. The LIBS spectra were analyzed using advanced multivariate statistical signal processing techniques. Partial least squares discriminant analysis (PLSDA) resulted in a correct place-level geographic classification at success rates above 90%. The possible role of rare-earth elements (REEs) as a factor contributing to the high levels of sample discrimination was explored. These results provide additional evidence that LIBS has the potential to be utilized in the field as a real-time screening tool to discriminate between columbite–tantalite ores of different provenance.}, journal={SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY}, author={Hark, Richard R. and Remus, Jeremiah J. and East, Lucille J. and Harmon, Russell S. and Wise, Michael A. and Tansi, Benjamin M. and Shughrue, Katrina M. and Dunsin, Kehinde S. and Liu, Chunyi}, year={2012}, pages={131–136} }
 @book{russell s. harmon_parker_2011, title={Frontiers in geochemistry contribution of geochemistry to the study of the earth}, publisher={Chichester, West Sussex, UK ;|aHoboken, NJ: Wiley-Blackwell}, author={Russell S. Harmon and Parker, Andrew}, year={2011} }
 @article{wegner_woerner_harmon_jicha_2011, title={Magmatic history and evolution of the Central American Land Bridge in Panama since Cretaceous times}, volume={123}, ISSN={["0016-7606"]}, DOI={10.1130/b30109.1}, abstractNote={Chemical compositions for 310 igneous rocks from the Cordillera de Panama and the Sona and Azuero peninsulas were supplemented by 40 Ar/ 39 Ar dating and Sr-, Nd-, Pb-, and O-isotope analysis to determine the magmatic evolution and oceanic plate interactions over the past 100 Ma in western Panama. An initial phase of intraplate magmatism, having geochemical characteristics of the Galapagos hotspot, formed the oceanic basement of the Caribbean large igneous province from 139 to 69 Ma. Younger accreted terranes with enriched trace element patterns (accreted ocean island basalt [OIB]) were amalgamated between 70 and 20 Ma. A second magmatic phase in the Azuero and Sona peninsulas has trace element patterns (Sona-Azuero arc) suggesting the initiation of subduction at 71–69 Ma. Arc magmatism continued in the Chagres basin region (Chagres-Bayano arc) from 68 to 40 Ma. A third phase formed discrete volcanic centers across the Cordillera de Panama (Cordilleran arc) from 19 to 5 Ma. The youngest phase consists of isolated volcanic centers of adakitic composition (Adakite suite) in the Cordillera de Panama that developed over the past 2 million years. Initiation of arc magmatism at 71 Ma coincides with the cessation of Galapagos plateau formation, suggesting a causal link. The transition from intraplate to arc magmatism occurred relatively quickly and introduced a new enriched mantle source. The arc magmatism involved progressive transition to more homogeneous intermediate mantle wedge compositions through mixing and homogenization of subarc magma sources through time and/or the replacement of the mantle wedge by a homogeneous, relatively undeleted asthenospheric mantle. Adakite volcanism started after a magmatic gap, enabled by the formation of a slab window.}, number={3-4}, journal={GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, author={Wegner, Wencke and Woerner, Gerhard and Harmon, Russell S. and Jicha, Brian R.}, year={2011}, pages={703–724} }
 @article{tateosian_mitasova_harmon_fogleman_weaver_harmon_2010, title={TanGeoMS: Tangible Geospatial Modeling System}, volume={16}, ISSN={["1941-0506"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78149238565&partnerID=MN8TOARS}, DOI={10.1109/tvcg.2010.202}, abstractNote={We present TanGeoMS, a tangible geospatial modeling visualization system that couples a laser scanner, projector, and a flexible physical three-dimensional model with a standard geospatial information system (GIS) to create a tangible user interface for terrain data. TanGeoMS projects an image of real-world data onto a physical terrain model. Users can alter the topography of the model by modifying the clay surface or placing additional objects on the surface. The modified model is captured by an overhead laser scanner then imported into a GIS for analysis and simulation of real-world processes. The results are projected back onto the surface of the model providing feedback on the impact of the modifications on terrain parameters and simulated processes. Interaction with a physical model is highly intuitive, allowing users to base initial design decisions on geospatial data, test the impact of these decisions in GIS simulations, and use the feedback to improve their design. We demonstrate the system on three applications: investigating runoff management within a watershed, assessing the impact of storm surge on barrier islands, and exploring landscape rehabilitation in military training areas.}, number={6}, journal={IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS}, author={Tateosian, Laura G. and Mitasova, Helena and Harmon, Brendan A. and Fogleman, Brent and Weaver, Katherine and Harmon, Russel S.}, year={2010}, pages={1605–1612} }
 @article{harmon_lyons_long_ogden_mitasova_gardner_welch_witherow_2009, title={Geochemistry of four tropical montane watersheds, Central Panama}, volume={24}, ISSN={["0883-2927"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-62849118013&partnerID=MN8TOARS}, DOI={10.1016/j.apgeochem.2008.12.014}, abstractNote={The major element chemistry was determined for surface waters from four watersheds in Central Panama during the 2005 dry season to ascertain geochemical patterns resulting from differing geology and human influences as well to estimate chemical denudation rates for this montane region of tropical rain forest. The Upper Rio Chagres (580 km2), Rio Pequini (281 km2) and Rio Cuango (175 km2) watersheds are formed on a geologically mixed terrain that consists of strongly hydrothermally altered andesite and volumetrically subordinate mafic-intermediate volcanic rocks and felsic intrusive lithologies, whereas the Rio Pacora watershed (374 km2) is developed largely on gabbroic and dioritic lithologies. The headwater areas of all four river basins lie in pristine tropical rainforest, with the Rio Cuango, Rio Pequini and Rio Pacora subject to varying degrees of different land uses in their middle to lower reaches. Values of pH for the four watersheds are near neutral to slightly alkaline (7.0–8.5), DO saturation is high (typically >90%) and dissolved solute contents of the rivers and tributary streams are low (SPC = 130 ± 31 μS/cm), documenting the overall pristine quality of the waters in all four basins. Cluster analysis, supported by a comparison of elemental variations, indicates a broad geochemical similarity of rivers and streams in the four watersheds, but also reveals subtle differences that can be attributed to lithologic control rather than anthropogenic influences. Low-order streams in the Pacora watershed have distinctly higher TDS values plus silica and Ca2+ concentrations than those forming in the mixed lithology terrain. Streams and rivers developed on mafic terrain are also slightly more enriched in total dissolved cations (TZ+) and HCO3-, relative to silica, than streams and rivers developed in the mixed lithology terrain. Potassium concentrations are uniformly low, and like Mg2+ and Na+, are similar in both terrains. Calcium/Mg ratios for all watersheds are lower than the world river average, indicating the importance of the weathering of Mg-rich minerals. The Ca/Na, HCO3/Na and Mg/Na ratios for the Rio Pacora streams and rivers fall within the mid-range of what has been observed globally for other streams/rivers draining mafic rocks. The chemical weathering rate calculated is 108 tons/km2/a, which is about 40% of the physical denudation rate for the Upper Rio Chagres watershed of 275–289 tons/km2/a. The results of this study document that both chemical and physical erosion rates within tropical montane watersheds in central Panama are significant in a global context.}, number={4}, journal={APPLIED GEOCHEMISTRY}, author={Harmon, Russell S. and Lyons, W. Berry and Long, David T. and Ogden, Fred L. and Mitasova, Helena and Gardner, Christopher B. and Welch, Kathleen A. and Witherow, Rebecca A.}, year={2009}, month={Apr}, pages={624–640} }
 @article{harmon_2009, title={IAGC Celebrates 40 Years}, volume={24}, ISSN={["0883-2927"]}, DOI={10.1016/j.apgeochem.2009.02.018}, number={6}, journal={APPLIED GEOCHEMISTRY}, author={Harmon, Russell S.}, year={2009}, month={Jun}, pages={1044–1046} }
 @article{pelletier_mitasova_harmon_overton_2009, title={The effects of interdune vegetation changes on eolian dune field evolution: a numerical-modeling case study at Jockey's Ridge, North Carolina, USA}, volume={34}, ISSN={["1096-9837"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-69749085481&partnerID=MN8TOARS}, DOI={10.1002/esp.1809}, abstractNote={Abstract}, number={9}, journal={EARTH SURFACE PROCESSES AND LANDFORMS}, author={Pelletier, Jon D. and Mitasova, Helena and Harmon, Russell S. and Overton, Margery}, year={2009}, month={Jul}, pages={1245–1254} }
 @article{mitasova_overton_harmon_2005, title={Geospatial analysis of a coastal sand dune field evolution: Jockey's Ridge, North Carolina}, volume={72}, ISSN={["1872-695X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-28744438601&partnerID=MN8TOARS}, DOI={10.1016/j.geomorph.2005.06.001}, abstractNote={Preservation and effective management of highly dynamic coastal features located in areas under development pressures requires in-depth understanding of their evolution. Modern geospatial technologies such as lidar, real time kinematic GPS, and three-dimensional GIS provide tools for efficient acquisition of high resolution data, geospatial analysis, feature extraction, and quantification of change. These techniques were applied to the Jockey's Ridge, North Carolina, the largest active dune field on the east coast of the United States, with the goal to quantify its deflation and rapid horizontal migration. Digitized contours, photogrammetric, lidar and GPS point data were used to compute a multitemporal elevation model of the dune field capturing its evolution for the period of 1974– 2004. In addition, peak elevation data were available for 1915 and 1953. Analysis revealed possible rapid growth of the dune complex between 1915–1953, followed by a slower rate of deflation that continues today. The main dune peak grew from 20.1 m in 1915 to 41.8 m in 1953 and has since eroded to 21.9 m in 2004. Two of the smaller peaks within the dune complex have recently gained elevation, approaching the current height of the main dune. Steady annual rate of main peak elevation loss since 1953 suggests that increase in the number of visitors after the park was established in 1974 had little effect on the rate of dune deflation. Horizontal dune migration of 3–6 m/yr in southerly direction has carried the sand out of the park boundaries and threatened several houses. As a result, the south dune section was removed and the sand was placed at the northern end of the park to serve as a potential source. Sand fencing has been an effective management strategy for both slowing the dune migration and forcing growth in dune elevation. Understanding the causes of the current movements can point to potential solutions and suggest new perspectives on management of the dune as a tourist attraction and as a recreation site, while preserving its unique geomorphic character and dynamic behavior.}, number={1-4}, journal={GEOMORPHOLOGY}, author={Mitasova, H and Overton, M and Harmon, RS}, year={2005}, month={Dec}, pages={204–221} }