Short-wave Infrared Spectroscopy Research Articles

Alteration mineralogy, characteristics and shortwave infrared spectroscopy of white mica in the Zijinshan ore field, Fujian Province: Implications for porphyry Cu prospecting

The Zijinshan ore field is situated in the southeastern part of China. in which contains the large Zijinshan high-sulfidation Cu-Au deposit, the Luoboling porphyry Cu-Mo deposit, the Yueyang low-sulfidation Au-Ag deposit, the Longjiangting and the Wuziqilong tansitional Cu deposit, and the Xi’nan porphyry Cu-Mo prospect. Debates on genetic relationship among these deposits, especially the relationship between the Zijinshan Cu-Au deposit and the adjacent Luoboling deposit is a question of importance for further exploration in this ore field. In this contribution, the alteration mineralogy, alteration texture, zonation and mineral chemistry, in combination with shortwave infrared spectroscopy (SWIR) analysis of white mica were used to help focus exploration and assessment of hydrothermal deposits in the Zijinshan ore field.In this study, diaspore-pyrophyllite alteration zone, chlorite-sericite alteration zone and propylitic alteration zone were first identified in the deep drill core of the Zijinshan Cu-Au deposit, which gives way upward to quartz-alunite-kaolinite zone, quartz-alunite zone and the silicic alteration zone. In the Xi’nan Cu-Mo prospect, diaspore-pyrophyllite alteration zone was first recognized in the shallow level with the chlorite-sericite alteration zone and propylitic alteration zone in the deeper level. Andalusite- sericite ± diaspore alteration zone was first recognized in the upper part of the Luoboling Cu-Mo deposit and the deeper part of the Wuziqilong Cu deposit. It indicates that a pervasive occurrence of diaspore -pyrophyllite ± andalusite alteration zones in the Zijinshan ore field, which may potentially represent a transitional environment between the top of porphyry alteration zones and the base of advanced argillic alteration zones. Minerals of the white mica group are extensively distributed in various alteration zones of the Zijinshan ore field. The SWIR analysis of white mica indicated that the wavelength position of the Al-OH (∼2,200 nm; wAlOH) absorption feature increases gradually from the shallow kaolinite-dickite alteration zone to the deep potassic alteration zone. In the advanced argillic alteration zones, the range of wAlOH values of white mica is less than 2205 nm. Conversely, in the porphyry alteration zones, it always exceeds 2205 nm. It is evident that the andalusite-sericite alteration zone with higher wAlOH values (average of 2203 nm) is always proximal to the porphyry mineralization, which may act as indicators for deep porphyry prospecting. The results of electron probe microanalysis (EPMA) reveal that the early enrichment of Mg and depletion of Fe in white mica can be attributed to the preferential incorporation of Fe into iron oxides and iron sulfides in the potassic and propylitic alteration zones. Overall, there is a negative correlation between wAlOH and Al, while wAlOH exhibits a positive correlation with the sum of Fe + Mg + Mn. The distribution characteristics of alteration zones and the variation patterns of the wAlOH of white mica indicate that there are probably several paleo-thermal centers in the deep parts of the Zijinshan ore field, located respectively in the deep parts of the Xi’nan Cu-Mo prospect and the deep part of the Zijinshan Cu-Au deposit and the deep parts of the Wuziqilong Cu deposit, and the latest seems to be more fertile and deserves further exploration.

Rapid non-destructive evaluation of texture properties changes in crispy tilapia during crispiness using hyperspectral imaging and data fusion

In this study, two distinct hyperspectral imaging systems, the Visible and Near-Infrared Spectroscopy (VNIR) and the Short-Wave Infrared Spectroscopy (SWIR), were employed in combine with chemometric techniques to examine the alterations in the texture properties (hardness, resilience, chewiness, and cohesiveness) of tilapia during the crispy process. Partial least squares regression (PLSR) was used to establish a linear relationship between the spectral reflectance values and the different texture parameters of tilapia, and various preprocessing, variable selection, and data fusion (Low-Level Fusion (LLF) and Mid-Level Fusion (MLF)) methods were considered to optimize the calibration model. For hardness, with RP, RMSEP, %RMSEP and RPD values of 0.63, 5.84, 21.65% and 1.26 respectively. For resilience, the LLF presented superior performance, with RP, RMSEP, %RMSEP and RPD values of 0.92, 0.03, 6.8% and 2.52 respectively. For chewiness, the MLF presented superior performance, with RP, RMSEP, %RMSEP and RPD values of 0.68, 4.03, 23.05% and 1.36. For cohesiveness, the MLF exhibited the best performance, with RP, RMSEP, %RMSEP and RPD values of 0.82, 0.03, 4.85% and 1.65 respectively. It was demonstrated that the fusion of both hyperspectral datasets provides a promising method for non-destructive texture measurement of tilapia at different stages of crispiness.

A Characterization Approach for End-of-Life Textile Recovery Based on Short-Wave Infrared Spectroscopy

Reusing and recycling End-Of-Life (EoL) textiles is a successful approach to develop sustainable and circular strategies in the apparel industry. Textile reuse and recycling can help to reduce the environmental impact of the fashion and textile industry by preserving natural resources and reducing waste. Textile fibers recognition and sorting, according to material composition, are of primary importance for the implementation of efficient and sustainable recycling strategies. In this work, Short-Wave InfraRed (SWIR: 1000–2500 nm) spectroscopy was applied to extract information regarding the fabric composition of different EoL textiles in order to set up a hierarchical classification procedure able to recognize different type of textile. In more detail, Partial Least Squares-Discriminant Analysis (PLS-DA) pattern recognition technique was used and classifications were performed in two steps: (1) recognition of the fiber origin [i.e. plant-derived, animal-derived, artificial textiles such as synthetic and/or Man-Made Cellulosic Fibers (MMCFs)] and, (2) discrimination of fabrics according to the material classes (i.e. silk, cotton, wool, viscose, linen, jute, polyester and blends). The proposed chemometric technique successfully classified textiles based on their spectral properties. The acquired results are highly promising and provide important insight into the EoL textile recycling business. These analytical techniques have the potential to be utilized to successfully automate the recycling process, either in addition to or as a replacement for manual processes, hence improving sorting procedures.Graphical

Characteristics of the shortwave-thermal infrared spectra of the Zhuxi superlarge tungsten deposit in Jiangxi Province and their exploration significance

Infrared spectroscopy, as an innovative exploration tool, enables rapid identification of alteration minerals, thus can facilitate an improved understanding of mineralization and enhance prospecting efficiency. This paper specifically applies this methodology to drill core samples from the Zhuxi Deposit, Jiangxi Province, the world's largest tungsten deposit. Using shortwave and thermal infrared spectroscopy, this study aims to identify spectral characteristics of typical altered minerals within the deposit, establish the mineral identification methods and preferred spectrum bands, and discern spectral characteristics of varied altered mineral combinations. The variations observed in the characteristic bands of these isomorphic minerals serve as indicators of changes in the ore-forming environment. Specifically, absorption features around 2190 nm are indicative of paragonite formation in low-temperature environments, while features around 2210–2225 nm signify the presence of phengite in high-pressure, high-temperature conditions. Absorption at 2260 nm is characteristic of Fe-rich chlorite, suggesting a low-temperature, reducing environment, whereas Mg-rich chlorite exhibits absorption at 2250 nm, indicative of a higher-temperature environment. Based on depth, the deposit can be classified into three types of alteration mineralization: greisen, garnet skarn, and diopside skarn. Shortwave infrared spectroscopy proves effective for identifying muscovite in greisen and altered minerals such as serpentine and chlorite in diopside skarn. Thermal infrared spectroscopy, on the other hand, is ideal for quartz identification in greisen and garnet in garnet skarn. Intriguingly, the study finds that the absorption characteristics of garnet can reflect the metal mineralization type of the deposit. The absorption valley wavelength of garnet varies from around 11290–11380 nm in non-mineralized or poorly mineralized samples, to 11230–11290 nm when scheelite mineralization dominates, and to 11180–11230 nm when both scheelite and chalcopyrite are present. These findings contribute significantly to our understanding of the mineralogical characteristics and genetic environment of the Zhuxi deposit. Moreover, they provide valuable insights into the potential application of infrared spectroscopy for skarn zonation and mineral exploration.

Wavelength Calibration for the LIBS Spectra of the Zhurong Mars Rover

China’s first Mars rover, Zhurong, landed on the southern region of Utopia Planitia, Mars, on 14 May 2021 (UTC). Zhurong is equipped with the Mars Surface Composition Detection Package (MarSCoDe), which analyzes the Martian surface’s material composition. Composed of laser-induced breakdown spectroscopy (LIBS), short-wave infrared spectroscopy (SWIR), and a microimaging camera, MarsCoDe can work at a distance of 1.6–7 m to analyze element abundance and the mineralogy of targets on the Martian surface. Analysis shows that the wavelengths of MarSCoDe onboard LIBS spectra acquired within the same probe period will have different degrees of drift, leading to deviation in qualitative and quantitative elemental analysis. This paper finds that the spectrum drift follows a quadratic function relationship with the CCD temperature of the MarSCoDe spectrometer, based on which a wavelength calibration method is established. According to the function, the drift of a certain channel is calculated by the corresponding CCD temperature, and then the wavelength of the spectrum is calibrated by the drift. The accuracy of this calibration method for the position of peak wavelength in the LIBS spectrum can reach about 1/5 of the apparatus spectral width, and the cross-validation analysis using a norite standard sample shows that it is comparable to the wavelength calibration accuracy of the ChemCam onboard data product.

An Investigation on Bromine Content Assessment in e-Waste Plastics by Short Wave Infrared (SWIR) Spectroscopy

This paper reported a study based on the application of SWIR (shortwave infrared) spectroscopy to assess the presence of brominated flame retardants (BFRs) in plastic scraps coming from an e-waste stream composed by CRT (i.e., cathode-ray tube) monitors and televisions. An X-ray fluorescence (XRF) analysis was performed on plastic scraps to determine the presence and content of bromine (Br). The presence in plastic waste-flow streams, fed to or resulting from a recycling process, of individuals characterized by high concentrations of Br does not allow their use as secondary raw materials, imposing the need for an ad hoc separation processes. Chemometric methods were adopted for setting up models able to discriminate Br content. In more detail, principal component analysis (PCA) was used as an exploratory tool, while partial least squares (PLS) and locally weighted regression based on PLS regressions (LWRPLS) were used as multivariate regression models to test the ability of the spectra to predict Br content. The LWRPLS, showing an Rp2 of about 0.9, demonstrates the ability of this algorithm to establish a good correlation between the spectral signatures of plastic scraps and their Br content.

Fungi Classification in Various Growth Stages Using Shortwave Infrared (SWIR) Spectroscopy and Machine Learning.

Dark septate endophytes (DSEs) fungi are beneficial to host plants with regard to abiotic stress. Here, we examined the capability of SWIR spectroscopy to classify fungus types and detected the growth stages of DSEs fungi in a timely, non-destructive and time-saving manner. The SWIR spectral data of five DSEs fungi in six growth stages were collected, and three pre-processing methods and sensitivity analysis (SA) variable selection methods were performed using a machine learning model. The results showed that the De-trending + first Derivative (DET_FST) processing spectra combined with the support vector machine (SVM) model yielded the best classification accuracy for fungi classification at different growth stages and growth stage detection on different fungus types. The mean accuracy of generic model for fungi classification and growth stage detection are 0.92 and 0.99 on the calibration set, respectively. Seven important bands, 1164, 1456, 2081, 2272, 2278, 2448 and 2481 nm, were found to be related to the SVM fungi classification. This study provides a rapid and efficient method for the classification of fungi in different growth stages and the detection of fungi growth stage of various types of fungi and could serve as a tool for fungi study.

Application of Vis-NIR and SWIR spectroscopy for the segregation of bison muscles based on their color stability

The study objective was to investigate the potential for using visible near-infrared (Vis-NIR) and short wave infrared (SWIR) spectroscopy to segregate bison portions based on muscle types and storage periods. In the Vis-NIR range, the principal component analysis showed clear segregation of the muscles based on storage at retail display d 4 whereas the discrimination based on muscle type was better portrayed in the SWIR region. Furthermore, partial least squares discriminant analysis (PLS-DA) models classified muscles based on muscle type and storage in the Vis-NIR range with the classification accuracy of 97% for calibration and 86% for cross-validation. Finally, the PLS-regression models were developed for the successful prediction of a* value with an R2 of 0.88 (RMSEC: 1.57), 0.84 (RMSECV: 1.88), and 0.90 (RMSEP: 1.41), color score with an R2 of 0.96 (0.25), 0.95 (0.27), and 0.92 (0.32), and discoloration score with an R2 of 0.96 (0.47), 0.93 (0.63), and 0.93 (0.56) for calibration, cross-validation, and prediction, respectively.

Ni2+-Doped Garnet Solid-Solution Phosphor-Converted Broadband Shortwave Infrared Light-Emitting Diodes toward Spectroscopy Application.

Broadband shortwave infrared (SWIR) light-emitting diodes (LEDs), capable of advancing the next-generation solid-state smart invisible lighting technology, have sparked tremendous interest and will launch ground-breaking spectroscopy and instrumental applications. Nevertheless, the device performance is still suppressed by the low quantum efficiency and limited emission bandwidth of the critical phosphor layer. Herein, we report a high-performance Ni2+-doped garnet solid-solution broadband SWIR emitter centered at ∼1450 nm with a large full-width at half-maximum of ∼300 nm, thereby fabricating, for the first time, a directly excited Ni2+-doped garnet solid-solution phosphor-converted broadband SWIR LED device. A synergetic enhancement strategy, adding a fluxing agent and a charge compensator simultaneously, is proposed to deliver a more than 20-fold increase of the SWIR emission intensity and nearly 2-fold improvement of the thermal quenching behavior. The site occupation and mechanism behind the synergetic enhancement strategy are elucidated by a combination of experimental study and theoretical calculation. A prototype of the SWIR LED with a radiation flux of 1.25 mW is fabricated and utilized as an invisible SWIR light source to demonstrate the SWIR spectroscopy applications. This work not only opens a window to explore novel broadband SWIR phosphors but also provides a synergetic strategy to remarkably improve the performance of artificial SWIR LED light sources.

Directional Effect of Shortwave Infrared Spectroscopy Radiation of High-Temperature Target

Directional Effect of Shortwave Infrared Spectroscopy Radiation of High-Temperature Target

Detection of Brominated Plastics from E-Waste by Short-Wave Infrared Spectroscopy

In this work, the application of Short-Wave Infrared (SWIR: 1000–2500 nm) spectroscopy was evaluated to identify plastic waste containing brominated flame retardants (BFRs) using two different technologies: a portable spectroradiometer, providing spectra of single spots, and a hyperspectral imaging (HSI) platform, acquiring spectral images. X-ray Fluorescence (XRF) analysis was preliminarily performed on plastic scraps to analyze their bromine content. Chemometric methods were then applied to identify brominated plastics and polymer types. Principal Component Analysis (PCA) was carried out to explore collected data and define the best preprocessing strategies, followed by Partial Least Squares—Discriminant Analysis (PLS-DA), used as a classification method. Plastic fragments were classified into “High Br content” (Br > 2000 mg/kg) and “Low Br content” (Br < 2000 mg/kg). The identified polymers were acrylonitrile butadiene styrene (ABS) and polystyrene (PS). Correct recognition of 89–90%, independently from the applied technique, was achieved for brominated plastics, whereas a correct recognition ranging from 81 to 89% for polymer type was reached. The study demonstrated as a systematic utilization of both the approaches at the industrial level and/or at laboratory scale for quality control can be envisaged especially considering their ease of use and the short detection response.

Broadband Short-Wave Infrared Light-Emitting Diodes Based on Cr3+-Doped LiScGeO4 Phosphor

Short-wave infrared (SWIR) spectroscopy has recently emerged as an important technology across a wide range of areas, whether industrial, biomedical, or environmental. Nevertheless, it is still a long-standing challenge to develop robust SWIR light sources. The SWIR phosphor-convert light emitting diodes (LEDs) by coating blue LED chips with desirable SWIR-emitting phosphors are becoming an ideal alternative for solid-state SWIR light sources due to its compactness, low-cost, and long operating lifetime, as does the commercial white LEDs. Herein, we report a blue-pumped Cr3+-doped LiScGeO4 SWIR phosphor as a luminescent converter for phosphor-convert SWIR LEDs. This phosphor shows an intense SWIR emission band with a peak wavelength at ∼1120 nm owing to the 4T2 → 4A2 electron transition of Cr3+ when exciting with blue light. The full width at half-maximum (fwhm) of the phosphor is ∼300 nm and the absolute quantum efficiency is determined to be ∼26%. SWIR LED prototypes are constructed by combining the optimized phosphor materials with commercial blue InGaN LED chips, which can generate a commendable emission band in the SWIR region over 800-1600 nm and achieve a maximum output power of ∼4.78 mW at 60 mA with the photoconversion efficiency of 4.4%. The current exploration of Cr3+-doped SWIR-emitting phosphors will lay the foundation to engineer phosphor-convert SWIR LEDs for applications in night-vision surveillance and SWIR spectroscopy technology. These blue-light-excitable SWIR-emitting phosphors can serve as an important complement to the spectral gap of the current Cr3+-doped phosphors in the SWIR region and will pave the way toward cost-effective phosphor-converted solid-state SWIR light sources.

Footprints of ore fluid pathway and implications to mineral exploration in the Shihu Gold Deposit, North China: Evidence from short wave infrared spectroscopy of illitic alteration rocks

Most hydrothermal ore deposits have experienced multiple stages of hydrothermal activities and the overprinting makes the footprints of ore fluid pathway difficult to identify, which prevents us from targeting the mineral resource effectively. In this paper, the altered wall-rocks from all accessible underground tunnels of No.101 lode in the Shihu Gold Deposit, North China were investigated by the combined methods of petrographic microscopy and short wave infrared spectroscopy (SWIR). The results show that there are three types of alteration in the Shihu Gold Deposit, i.e., the proximal illitic alteration, the transitional chloritic alteration and the distal propylitic alteration. The wavelength (wvl) of the 2200 nm absorption features (2200wvl) of the illitic alteration rocks around ore bodies are shorter than those from the barren areas, suggestive of the compositional variation of illites derived from the multiple stages of hydrothermal fluids. The domains with higher absorption depth at 1400 nm, 1900 nm and 2200 nm (1400D, 1900D and 2200D) are spatially coincident with the economic ore bodies, which is well in accordance with the field truth that the gold mineralization in the Shihu mining district is intimately related to illitic alteration. The band ratio of 2200D/1900D, which is regarded as the proxy to illite crystallinity, is positively related to the temperature of fluid inclusions. The coincidence between low crystallinity and gold mineralization reflects the fact that fluid temperature during the main mineralization stage was relatively low compared to those of previous stages. Detailed investigation indicated that the economic ore bodies mainly occurred in the structural dilation domains, i.e., the widened portions of the ore-controlling structure were more suitable for the fluids migration and probably acted as the fluid up-flow zones. Therefore, SWIR spectroscopy of illite is a powerful tool to trace the ore fluid pathway, which is crucial to the understanding and exploration of gold mineralization.Based on the geological significance of the SWIR signatures and the investigation of the ore-forming conditions, it can be concluded that there are two fluid up-flow zones in No.101 lode, one of which lies on the north of No.13 cross section and centered at No.7 cross section, whereas the other on the south of No.17 cross section and centered at No.27 cross section. As a result, two steeply dipped ore bodies were formed along the up-flow zones. According to this ore-forming analysis, the location centered at No.47 cross section with elevation below 150 m would be an ideal site for the formation of a third ore body. This has recently been verified by underground drillings in the Shihu Gold Deposit (Yougang Zhang, pers. commun. 2020).

Mapping Alteration Mineralogy in Eastern Tsogttsetsii, Mongolia, Based on the WorldView-3 and Field Shortwave-Infrared Spectroscopy Analyses

This study produces alteration mineral maps based on WorldView-3 (WV-3) data and field shortwave-infrared (SWIR) spectroscopy. It is supported by conventional analytical methods such as X-ray diffraction, X-ray fluorescence, and electron probe X-ray micro analyzer as an initial step for mineral exploration in eastern Tsogttsetsii, Mongolia, where access is limited. Distributions of advanced argillic minerals (alunite, dickite, and kaolinite), illite/smectite (illite, smectite, and mixed-layered illite-smectite), and ammonium minerals (buddingtonite and NH4-illite) were mapped using the decorrelation stretch, band math, and mixture-tuned-matched filter (MTMF) techniques. The accuracy assessment of the WV-3 MTMF map using field SWIR data showed good WV-3 SWIR data accuracy for spectrally predominant alteration minerals such as alunite, kaolinite, buddingtonite, and NH4-illite. The combination of WV-3 SWIR mineral mapping and a drone photogrammetric-derived digital elevation model contributed to an understanding of the structural development of the hydrothermal system through visualization of the topographic and spatial distribution of surface alteration minerals. Field SWIR spectroscopy provided further detailed information regarding alteration minerals such as chemical variations of alunite, crystallinity of kaolinite, and aluminum abundance of illite that was unavailable in WV-3 SWIR data. Combining WV-3 SWIR data and field SWIR spectroscopy with conventional exploration methods can narrow the selection between deposit models and facilitate mineral exploration.

Identifying animate stones and sacred landscapes: Twenty-five years of native pipestone-quarries research in the American midcontinent

This paper assesses our current understanding of the native use of the major midcontinental United States pipestone quarries based on over two decades of research. Our studies indicate that combining chemical and mineralogical techniques such as shortwave infrared spectroscopy (SWIS), thin-section petrography, and X-ray diffraction (XRD) have identified pipestones with similar chemical compositions containing distinctive mineralogical suites (often including berthierine, kaolinite, diaspore, muscovite, and pyrophyllite). This research has identified unique mineral compositions at known quarries such as catlinite, Ohio Feurt Hill, Baraboo, and Barron pipestones, as well as identifying previously unknown quarries of Sterling Illinois pipestone, Cahokia Missouri flint clay, and Portsmouth Ohio Claystone. These discoveries have led to a major shift in interpretations of Cahokian and Hopewell pipe exchange. Further examination of native ethnographic quarry use identified the primary attraction of pipestone quarries lay in the perceived ritual and spiritual power of the stone rather than in its economic utility.

Mineralogical Study and Genetic Model of Efflorescent Salts and Crusts from Two Abandoned Tailings in the Taxco Mining District, Guerrero (Mexico)

The mineralogy of surface crusts and efflorescent salts of two old abandoned tailings (Xochula and Remedios) of the mining district of Taxco, Guerrero, was studied by short-wave infrared spectroscopy (SWIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The chemistry of the selected samples was studied with induced coupled plasma mass spectrometry (ICP–MS). Principal mineralogy is composed of hydrated sulfates of iron (di-trivalent), other less-soluble sulfates such as gypsum and jarosite, and oxides–hydroxides of iron, all of which are the result of the weathering of sulfides (mainly pyrite) accumulated in mining waste. Using quantitative X-ray diffraction (Rietveld method) and the spatial distribution of secondary minerals, two main zones (lateral and central) have been established in both tailings. The genetic model for their formation shows that the secondary iron minerals (sulfates, oxides, and hydroxides) in these deposits have been formed at least in three different stages, mainly by oxidation, dissolution, and precipitation processes in combination with dehydration and primary sulfides neutralization reactions. The chemical analyses of some salts confirm the presence of potentially toxic elements (PTE) in their structure and therefore indicate that the dissolution of the efflorescences in these deposits is a potential source of contamination during the wet season.

Solid-State Thin-Film Broadband Short-Wave Infrared Light Emitters.

Solid-state broadband light emitters in the visible have revolutionized today's lighting technology achieving compact footprints, flexible form factors, long lifetimes, and high energy saving, although their counterparts in the infrared are still in the development phase. To date, broadband emitters in the infrared have relied on phosphor-downconverted light emitters based on atomic optical transitions in transition metal or rare earth elements in the phosphor layer resulting in limited spectral bandwidths in the near-infrared and preventing their integration into electrically driven light-emitting diodes (LEDs). Herein, phosphor-converted LEDs based on engineered stacks of multi-bandgap colloidal quantum dots (CQDs) are reported as a novel class of broadband emitters covering a broad short-wave infrared (SWIR) spectrum from 1050-1650 nm with a full-width-half-maximum of 400 nm, delivering 14 mW of optical power with a quantum efficiency of 5.4% and power conversion efficiency of 13%. Leveraging the electrical conductivity of the CQD stacks, further, the first broadband SWIR-active LED is demonstrated, paving the way toward complementary metal-oxide-semiconductor integrated broadband emitters for on-chip spectrometers and low-cost volume manufacturing. SWIR spectroscopy is employed to illustrate the practical relevance of the emitters in food and material identification case studies.

Ammonium abundance and short-wave infrared absorption spectra of altered rocks

Rhyolitic rocks hosting the El Zapote epithermal Ag deposit are pervasively altered and contain ammonium ranging from 290 to 1750 ppm. High ammonium values are found in samples containing abundant fine-grained illite. This fine-grained illite shows overall low ratios of K/(Al + Fe), likely due to ammonium substituting K+. Samples containing high ammonium, greater than 1000 ppm in the proximity of Ag-bearing veins, show distinct absorption features of ammonium in short-wave infrared (SWIR) absorption spectra. Samples containing ammonium ranging from 500 to 1000 ppm show mixed absorption signatures; some show prominent absorption features related to ammonium, whereas others have no recognizable features. There is no discernible absorption feature related to ammonium for samples containing less than 500 ppm NH4. The data suggest that SWIR spectroscopy is useful in locating the proximal areas to mineralization, but the extent of ammonium alteration is much larger than that identified by SWIR spectroscopy. Nitrogen isotope compositions of ammonium are similar to those of sedimentary rocks, suggesting that the source of ammonium in altered rhyolite is sedimentary basement rocks in the area.Supplementary material: bulk rock composition is available at https://doi.org/10.6084/m9.figshare.c.5015663

116 Short Wave Infrared Light Imaging Distinguishes Superficial from Deep Burns

Abstract Introduction Burns represent a significant public health burden that rely on accurate diagnosis of burn depth. The gold standard for burn injury depth remains visual clinician appraisal. Candidate modalities for objective and standardized diagnostics have failed to reach wide adoption due to limitations in practicality, cost, and reproducibility. Here we utilize short wave infrared spectroscopy (SWIR) which involves analysis of a subset of the infrared spectrum, between 1000–2500 nm, and has previously been described in the assessment of water composition in human skin. Given literature highlighting moisture as a potential biomarker for tissue viability, we hypothesized a similar application in a novel, healthcare context for assessing tissue damage following contact burn injury. Methods A custom imaging system was constructed with tungsten-filament light source, filters centered at 1200, 1650, 1940, and 2250 nm, and a SWIR camera. Phantom models of agar slabs were constructed at 1, 2, 3, 5, and 10 mm thickness and spectrally interrogated in epi-illumination and trans-illumination configurations (Fig A, top). For verification of moisture detection, filter paper was wetted with 50 µL H2O and imaged. For burns study, Yorkshire pigs (N=5) were injured with both short (20 s) and long (40 s) exposure burns to assess varying degrees of burn injury for SWIR and biopsy histology (H&E, picrosirius). In vivo imaging occurred 72 hours after burn injury. For quantifications, a 50x50 pixel region was selected from the center of each burn site to determine average reflectance. Results Absorbance of SWIR light was found to depend on agar thickness, increasing with depth and moisture in substrates. 1940 nm absorbance was sensitive with full absorbance even in agar slabs as thin as 1 mm (Fig A, bottom). Water directly applied to paper demonstrated sharp demarcation of dry vs. wet regions consistent with absorptive patterns seen in agar (Fig B). Short (S) and long (L) regions of porcine burns were imaged (Fig C-D). Two-way ANOVA analysis across 5 animals revealed that reflected fraction was different for each wavelength (p< 0.001) and for both burn exposure times (p=0.011). Imaged wavelengths of 1200, 1650 and 2250, but not 1940 nm, showed a significant 10–20% higher reflectance in the long duration burn in comparison to the short or unburned regions (Fig E). Analysis of biopsies in each treatment region confirmed deeper damage with longer injury times (long: 922±45 vs short: 590±57 mm, n=10/group, p< 0.001, Fig F). Conclusions There exists a need in burn care for a reliable, objective measure of tissue viability following burn injury. SWIR spectroscopy can delineate moisture content in phantom models and distinguish burn depth in porcine models. Applicability of Research to Practice This work to be particularly timely given the need and demand for more objective diagnostic modalities in contemporary burn depth assessment.

How Do Secondary Minerals in Granite Help Distinguish Paleo- from Present-Day Permeable Fracture Zones? Joint Interpretation of SWIR Spectroscopy and Geophysical Logs in the Geothermal Wells of Northern Alsace

The investigation of permeable hydrothermally altered and fractured zones and their distribution is a key issue for the understanding of fluid circulation in granitic rocks, on which the success of geothermal projects relies. Based on the use of short-wave infrared (SWIR) spectroscopy applied to rock cuttings coupled with interpretation of geophysical logs, we propose an investigation of the clay signature of fault and fracture zones (FZ) inside the granitic basement. This methodology was applied to two geothermal wells: GRT-2 from the Rittershoffen and GPK-1 from the Soultz-sous-Forêts (Soultz) geothermal sites, both located in the Upper Rhine Graben (URG). A total of 1430 SWIR spectra were acquired and analysed. Variations in the 2200 nm absorption band area are correlated with hydrothermal alteration grades. The 2200 nm absorption band area is found to reflect the illite quantity and its variations in the granitic basement. Low, stable values are observed in the unaltered granite facies, showing good reproducibility of the method, whereas scattered high values are associated with high hydrothermal alteration and FZs. Variations in the 2200 nm absorption band area were correlated with the gamma ray and electrical resistivity logs. This procedure allowed us to confirm that illite mainly controls the resistivity response except inside the permeable FZs, where the resistivity response is controlled by the geothermal brine. Thus, the architecture of these permeable FZs was described precisely by using a combination of the 2200 nm absorption band area data and the electrical resistivity log. Moreover, by correlation with other geophysical logs (temperature (T), porosity, and density), paleo-permeable and currently permeable FZs inside the reservoir were distinguished. The correlation of SWIR spectroscopy with electrical resistivity logs appears to be a robust tool for geothermal exploration in granitic reservoirs in the URG.