Laser Raman Analysis Research Articles

The superposition of Cretaceous mineralization events leading to the formation of the large Baiyinnuoer Pb–Zn deposit in NE China

The Baiyinnuoer Pb–Zn deposit, estimated at 26.57 million metric tonnes (Mt) with grades of 1.77% Pb and 5.21% Zn, is situated in the southern Great Xing'an Range (SGXR) of northeast China. The deposit comprises southern and northern ore belts. The southern belt primarily contains skarn ore bodies (32% of reserves) associated with Triassic granodiorite, while the northern belt is dominated by skarn ore bodies (30% of reserves) related to Triassic diorite porphyry. In addition to Triassic skarn‐type mineralization, the deposit also exhibits Early Cretaceous mineralization. This includes vein‐type occurrences (36% of reserves) within volcanic tuff and syenite porphyry, alongside a small amount of skarn ore bodies (2% of reserves) related to syenite porphyry. LA‐ICP‐MS U–Pb dating of intrusive rocks and garnets was conducted to investigate the timing and genesis of these mineralization events, revealing two distinct stages of skarn‐type mineralization. The first stage, associated with Early Triassic granitoids, dates to 254.6 ± 1.4–241.7 ± 2.7 Ma, while the second stage is closely associated with Early Cretaceous syenite porphyry, constrained to 135.4 ± 1.1–135.2 ± 1.6 Ma. Garnet U–Pb dating in the syenite porphyry‐related skarn yielded an age of 134.9 ± 4.7 Ma; however, due to low U content, reliable dating of garnets associated with Early Triassic granitoid‐related skarn was not feasible. Micro‐thermometry and Laser Raman analyses of fluid inclusions within vein‐type ore bodies highlighted distinct differences between vein‐type mineralization and Early Triassic skarn‐type mineralization. Additionally, in situ sulfur isotope analyses of sphalerite from both Early Triassic and Early Cretaceous ore bodies indicate a magmatic origin for sulfur in both stages. Through comprehensive geological, geochronological, in situ sulfur isotope and fluid inclusion studies, the Baiyinnuoer Pb–Zn deposit is conclusively identified as a large deposit characterized by two distinct periods of mineralization (Early Triassic and Early Cretaceous), akin to several other significant polymetallic deposits in NE China.

Genesis of the Yu'erya gold deposit, East Hebei, China: Insights from geology and fluid inclusions

The Yu'erya gold deposit is a large‐scale gold deposit in eastern Hebei. However, the ore genesis is controversial because the gold orebody is closely related to biotite granite in time and space. The hydrothermal processes of the Yu'erya gold deposit can be divided into early quartz (Q1)‐pyrite stage, middle quartz (Q2)‐sulphide stage and late quartz (Q3)‐calcite stage. The Q1 is subdivided into Q1‐1 and Q1‐2 generations by SEM‐CL images, and Q2 is subdivided into Q2‐1 and Q2‐2 generations. Three types of fluid inclusions (FIs), including aqueous‐carbonic type (C‐type), aqueous‐rich type (W‐type) and vapour‐rich type (V‐type), were observed in the Yu'erya gold deposit. The Q1‐1 is dominated by C‐type inclusions, and the other quartz is dominated by W‐type inclusions. Laser Raman analysis shows that the initial ore‐forming fluids mainly belong to the CO2‐H2O‐NaCl system and gradually transferred to the H2O‐NaCl system. The C‐type inclusions of Q1‐1 show the salinity of 3.1–10.1 (av. 6.9 ± 1.7) wt.% NaCl eqv., and the total homogenization temperature (Th) of 305–391°C. The homogenization temperature decreases gradually from the early to the late stage, with insignificant change in salinity, indicating that fluid cooling is the main precipitation mechanism. Trapping pressures of C‐type FIs are estimated at 206–284 MPa and 203–211 MPa for the early and middle stages, corresponding to the mineralization depths of 7.2–9.9 km and 7.1–7.4 km, respectively. The FIs in the early stage indicate that the initial ore‐forming fluids are characterized by low salinity and CO2 richness, which are different from those of the intrusion‐related gold deposits, but consistent with the orogenic gold deposits.

Organic Petrologic Characterization and Paleoenvironmental Analysis of Permian Shale in Northeast Sichuan Province, China

The Permian shale in Northeast Sichuan is an important shale oil and gas resource potential area, and the study of its organic matter characteristics and paleoenvironmental analysis is of great significance for revealing the shale oil and gas formation mechanism and resource evaluation. In this study, the organic matter of Permian shales in northeast Sichuan was carefully studied based on various analytical tools, such as petrology, laser Raman, microscopy, and principal trace elements, and the paleoenvironmental parameters of the shales were comprehensively analysed. A detailed study of the organic matter characteristics of Permian shales in northeast Sichuan reveals important features such as organic matter fractions, structural characteristics, maturity and sources. The results show that the organic matter of the shale consists mainly of solid bitumen, putrescine group, specular group and multicellular planktonic algae. Petrological observations and laser Raman analyses indicate a high maturity of the organic matter and a high content of organic carbon (TOC), showing good hydrocarbon potential. In this study, we reconstructed the palaeoenvironmental parameters and inferred the palaeoenvironmental evolution through palaeoenvironmental analyses of Permian shales in northeast Sichuan. The results of the comprehensive multi-indicator study show that the type of palaeoenvironment at the time of shale deposition was mainly an anoxic-reducing environment, and the depositional conditions were favourable to the enrichment and preservation of organic matter. In summary, the organic matter characteristics and paleoenvironmental analyses of the Permian shales in Northeast Sichuan provide important geological background information for an in-depth understanding of the formation mechanism, exploration potential and development prospect of shale hydrocarbons in this area. The results of this study can provide a scientific basis for the evaluation and development of shale oil and gas resources in this area, which is of great significance to geologists and the energy industry.

Contrasting fluids and implications for ore genesis in the Jiawula-Chaganbulagen Porphyry Mo-epithermal Pb[sbnd]Zn metallogenetic system: Evidence from fluid inclusions and H-O-He-Ar isotopes

The Jiawula-Chaganbulagen (Jia-Cha) ore field is located in the part of the southern Erguna Block of Northeast China and has significant mineralization potential. It comprises three deposits: The Chaganbulagen hydrothermal vein-type PbZn (Ag) deposit in the southeast, the Jiawula hydrothermal vein-type PbZn (Ag) deposit in the northwest, and the blind porphyry Mo mineralization in between. Previous geochronological dates, including molybdenite ReOs, zircon UPb, sulfide RbSr, and sericite ArAr, indicate that the formation of hydrothermal molybdenite and the PbZn mineralization were coeval and that they originated from a porphyry-epithermal metallogenetic system that was related to Early Cretaceous magmatism. However, our comprehensive analysis of fluid inclusions and H-O-He-Ar isotopes reveals dissimilarities in the features and sources of the fluids that form three different deposits. Both the Jiawula deposit and porphyry Mo mineralization have three distinct types of fluid inclusions, which comprise liquid-rich two-phase aqueous inclusions (L-type), vapor-rich two-phase inclusions (V-type), and daughter mineral-bearing three-phase inclusions (S-type). The HeAr (3He/4He = 1.32–1.51 Ra; 40Ar/36Ar = 300 to 324) and HO (δ18OH2O = − 13.4 ‰ to 4.1 ‰; δD= − 155.1 ‰ to −129.9 ‰) isotope analysis results suggest that the trap fluids originated from an H2O-NaCl magmatic fluid system, which experienced Mo mineralization with high-temperature transformed into medium-temperature fluids that were primarily of meteoric water in the late-stage (Jiawula PbZn (Ag) deposit). The Chaganbulagen PbZn (Ag) deposit features L-type and V-type inclusions, along with aqueous‑carbonic inclusions (C-type). The results of Laser Raman analysis reveal that the gas phases of the fluid inclusions present in Chaganbulagen contain three different compositions: H2O, CO2, and CH4. The HO isotope compositions (δ18OH2O = −18.8 ‰ to −11.6 ‰; δD = −166 ‰ to −131 ‰) and HeAr (3He/4He = 0.034–0.041 Ra; 40Ar/36Ar = 296–298) in quartz of the Chaganbulagen PbZn (Ag) deposit indicate that the crustal fluids (MASW) were the main source of the ore-forming fluids, and belonged to a H2O-NaCl-CO2-CH4 system, which had low-temperature and low-salinity characteristics. By combining previously published geochronological dates, we proposed a model to explain the difference in the evolution of the fluids.

Fluid Mixing, Organic Matter, and the Origin of Permian Carbonate-Hosted Pb-Zn Deposits in SW China: New Insights from the Fuli Deposit

The Fuli Pb-Zn deposit is situated at the southwestern margin of the Yangtze Block in Yunnan. The deposit, which is hosted in the Permian Yangxin Formation dolomite, is a recent discovery. Our study indicates a significant presence of fluid inclusions in sphalerite from the Fuli Pb-Zn deposit, with fewer inclusions observed in dolomite and calcite. We conducted comprehensive petrographic, microthermometric, and laser Raman analyses on the inclusions within sphalerite and dolomite. Additionally, six samples of dolomite from the mineralization period were selected for H-O isotope analysis. The results of our study reveal the characteristics of ore-forming fluids and explore the mechanisms of ore formation. The study results indicate that the Fuli Pb-Zn deposit is a low- to medium-temperature hydrothermal deposit with fluid inclusions mainly composed of two-phase gas-liquid inclusions. Salinity and homogenization temperature analyses affirmed that there are two types of fluids present, one with low salinity and the other with high salinity. Laser Raman tests demonstrated the presence of CH4, N2, and CO2 in the gas phase of the inclusions. Microthermometric analyses indicated that the sphalerite ore-forming fluids consist of a multicomponent system of Mg2+ and Ca2+ enriched fluids. The features of the ore-forming fluids in the Fuli deposit arise from a blend of high-temperature, low-salinity metamorphic fluids and low-temperature, high-salinity basin brines. The basin brines in question have the potential to emanate from the Youjiang Basin. The formation of the ore is ascribed to the TSR and the mixing of fluids. The combination of these processes provided the requisite materials (SO42−), catalysts (Mg2+), and reducing agents (organic matter, CH4, and H2S) required to initiate the thermochemical sulfate reduction (TSR). As the TSR proceeded, it caused a shift in the pH of the fluids, thus promoting the precipitation of metal sulfides.

Mineralization of the Liwu large-scale stratiform copper deposits in Sichuan Province, China: Constraints from fluid inclusions

The Liwu stratiform copper deposit is located in the NW Jianglang dome, western China. Current studies mainly focus on the genetic type and mineralization of this deposit. Detailed fluid inclusion characteristics of metallogenic period quartz veins were studied to reveal the ore-forming fluid features. Laser Raman analysis indicates that the ore-forming fluids is a H₂O-NaCl-CH₄ (-CO₂) system. Fluid inclusions microthermometry shows a homogenization temperature of 181–375°C and a salinity of 5.26%–16.99% for the disseminated-banded Cu-Zn mineralization; but a homogenization temperature of 142–343°C and a salinity of 5.41%–21.19% for the massive-veined Cu-Zn mineralization. These features suggest a medium–high temperature and a medium salinity for the ore-forming fluids. H-O isotopic data indicates that the ore-forming fluids were mainly from the metamorphic and magmatic water, plus minor formation water. And sulfur isotopic data indicates that sulfur was mainly derived from the formation and magmatic rocks. Metallogenesis of the disseminated-banded mineralization was mainly correlated with fluid mixing and water-rock reaction; whereas that of the massive-veined mineralization was mainly correlated with fluid boiling. The genetic type of the deposit is a medium-high temperature hydrothermal deposit related to magmatism and controlled by shear zones. This study is beneficial to understand the stratiform copper deposit.

Genesis of the Fenghuangshan gold deposit, eastern Hebei, China: Insights from ore geology, fluid inclusion and H–O–S isotopes

The Jidong area is a vital gold province in North China, including plenty of metamorphic rock-hosted gold deposits. Whether ore-forming fluids are magmatic or metamorphic remains controversial. The genesis for gold mineralization in this gold province is ambiguous. The Fenghuangshan gold deposit lies on the eastern fragment of the Jidong gold province. In this paper, we present a detailed study on ore geology, fluid inclusions, and stable isotopes for the deposit to illustrate the characteristics of ore-forming fluids and ore genesis.The deposit occurs as gold-bearing quartz vein and disseminated- and veinlet-type mineralization. The main orebody named 7# is hosted in migmatitic granite, controlled by NE trending secondary fracture system. Four hydrothermal mineralization stages were identified, including: (Ⅰ) white quartz, (II) pyrite-quartz, (III) quartz-polymetallic sulfide, and (IV) calcite-chlorite-quartz. The Stage II and III belong to main gold mineralization stage. Fluid inclusions from different stages show that a lowering trend of fluid inclusion homogenization temperature was observed. They ranged from 222 °C to 407 °C (early-stage), 144 °C to 375 °C (main-stage), and 86 °C to 174 °C (late-stage), respectively. The salinities of the ore-forming fluids were typically low, ranging from 0.83 to 15.47 wt% NaCl equivalent. On the basis of Laser Raman analysis and fluid inclusion microthermometry, the ore-forming fluids belonged to a low- to moderate-temperature, low-salinity H2O-NaCl-CO2 system. Fluid immiscibility gave rise to rapid gold deposition. The early-stage δD and δ18OH2O values from quartzs ranged from –96.4‰ to –92.5‰ and from 1.74‰ to 2.44‰, whereas main-stage fluids had δ18OH2O values of –4.10‰ to –3.50‰ and δD values of –91.5‰ to –89.5‰. The early- and main-stage sulfide δ34S values varied from –2.0‰ to + 2.2‰, with average values of + 0.4‰. H-O-S-isotope data indicated that the primary ore-forming fluids were magmatic water mixing meteoric water during mineralization, and ore-forming materials were derived from a homogeneous magmatic source. Ore geology, fluid inclusions, and stable isotopes illustrate that the Fenghuangshan gold deposit is a low- to moderate-temperature magmatic-hydrothermal gold deposit. Future deep-seated and surrounding gold exploration should center on this area.

Preparation of Metal-Oxide-Doped Li7P2S8Br0.25I0.75 Solid Electrolytes for All-Solid-State Lithium Batteries.

The all-solid-state lithium battery (ASSB) has received great attention due to its greater safety than the conventional lithium-ion battery (LIB). Sulfide-based inorganic solid electrolytes are an important component to fabricate the ASSB. But to attain a better performance, the ionic conductivity and electrochemical stability of the sulfide-based solid electrolytes need to be improved. In this work, we prepared the metal-oxide-doped/mixed Li7P2S8I0.75Br0.25 lithium superionic conductors by a dry ball-milling process. The high ionic conductivity was achieved by a low-temperature (200 °C) heat-treatment process. The metal-oxide-doped Li7P2S8I0.75Br0.25 solid electrolyte exhibited a higher ionic conductivity value of 7.3 mS cm-1 at room temperature than the bare Li7P2S8I0.75Br0.25 solid electrolyte. The structural characteristics of the prepared solid electrolytes were studied by solid NMR and laser Raman analysis. The electrochemical stability of the prepared solid electrolyte was studied by cyclic voltammetry and DC charge-discharge analysis. The addition of metal oxide increased the electrochemical stability and dry-air stability of the Li7P2S8I0.75Br0.25 solid electrolyte. The Ta2O5-doped Li7P2S8I0.75Br0.25 solid electrolyte was stable even after 300 charge-discharge DC cycles and also 100 h of dry-air exposure. Further, the Ta2O5-doped Li7P2S8I0.75Br0.25 solid electrolyte-based ASSB exhibited a high discharge capacity value of 184 mA h g-1 at 0.1 C rate with 66% initial cycle Coulombic efficiency.

Geneses of multi-stage carbonate minerals and their control on reservoir physical properties of dolomitic shales

The formation and distribution of carbonate minerals have important influences on reservoir development. The dissolution-precipitation effect plays an important role in controlling the reformation of reservoir physical properties. High-quality source rocks with abundant reserves exist in the Lower Permian Fengcheng Formation, Junggar Basin, China, and the basin reservoir contains a large amount of carbonate minerals. Multi-stage cementation and dissolution of these carbonate minerals have important influences on diagenesis-porosity evolution of the reservoirs. Because of the coupled influences of deep fluid transformation and volcanic activity in the diagenetic evolution of the Fengcheng Formation, it has experienced a complex evolution of carbonate minerals. In this study, through core observation, thin section, X-ray diffraction mineral composition, carbon and oxygen isotope, fluid inclusion homogenization temperature, and laser Raman and cathodoluminescence analysis, the material sources, development period, dissolution-precipitation reactions, and transformation mechanisms of carbonate minerals in the diagenetic evolution of the Fengcheng Formation reservoir were evaluated in detail. Finally, the controlling effect of multi-stage cementation of carbonate minerals on the reservoir physical properties was determined. The results showed that there are three stages of carbonate minerals in the Fengcheng Formation. The material source of the early carbonate was mainly terrigenous debris, and the formation temperature range was 30–70 °C. The material source of middle-late carbonate minerals was mainly decarboxylation of organic acid, and the formation temperature was 60–110 °C. In addition, some were generated through hydrothermal metasomatism at high ambient temperatures, up to 120 °C. In areas where early carbonate minerals are well developed, a large number of microcracks was more likely to form under the influence of tectonic movements, resulting in high-quality reservoirs. The formation of late carbonate minerals, which is the main reason for reservoir densification in the later stage of diagenesis, resulted in poor reservoir physical properties. This study provides information useful for predicting the distribution areas of favorable reservoirs in the Fengcheng Formation, and a theoretical basis and guidance for improving the accuracy of shale oil exploration and development.

Pressure Evolution Mechanism of Marine Shale Reservoirs and Shale Gas Accumulation Model: Evidence from Fluid Inclusions in the Wufeng–Longmaxi Formation in the Basin Margin Structural Transition Zone in Northern Guizhou Province, China

The Wufeng–Longmaxi Formation in northern Guizhou Province is the dominant shale gas exploration and development strata in China. This study investigates the Shixi and Daozhen synclines, which are located in the basin margin transition zone. This region experienced complex tectonic stages and superimposed transformations, resulting in heterogeneous preservation conditions and shale reservoir pressure evolution in different tectonic units of the Wufeng–Longmaxi Formation. Based on fluid inclusion analysis, the types of fluid inclusion and the fluid filling stages of the Wufeng–Longmaxi shale reservoir were determined by laser Raman analysis and homogenization temperature and salinity tests. It was found that the fluid inclusion density and paleopressure in each filling stage were then restored. The results confirm that: ① Both the Shixi syncline and Daozhen syncline Wufeng–Longmaxi shale reservoirs experienced two fluid filling phases, in the early Yanshanian and late Yanshanian–Himalayan, respectively. In the course of tectonic evolution, the Wufeng–Longmaxi Formation in the Shixi and Daozhen synclines experienced pressure relief to some extent during the two aforementioned key fluid charging periods but remained in overpressurized states overall; ② The Wufeng–Longmaxi Formations of the Shixi and Daozhen synclines are characterized by high-density methane inclusions; ③ Based on the differences in the structural preservation conditions, the pressure evolution mechanisms of the Wufeng–Longmaxi Formation Shales during the important tectonic evolution period in northern Guizhou Province were revealed. Furthermore, differential enrichment and accumulation models of shale gas were established and named “facing thrust structural sealing type (Shixi syncline)” and “reverse fault lateral blocking type (Daozhen syncline)”.

Preparation of Li7P2S8X-Type Solid Electrolytes with Complex Anions for All-Solid-State Lithium Battery Applications

To improve the energy/power density and safety of all-solid-state lithium batteries (ASSBs), sulfide-based solid electrolytes have recently attracted attention. Li7P2S8X solid electrolytes are believed to show highly comparable ionic conductivity and stability against lithium metal. In this study, complex anion-based Li7P2S8X solid electrolytes were prepared for the first time to achieve good stability against lithium metal anodes. The crystalline structure and the role of complex anions in tuning the crystal structure were analyzed using powder X-ray diffraction techniques. Laser Raman and nuclear magnetic spectroscopy analyses were performed to reveal the structural characteristics of complex anion-based Li7P2S8X solid electrolytes. Among all prepared solid electrolytes, the Li7.05Sn0.05P1.95S8(OH)0.25I0.75 solid electrolyte exhibited the highest ionic conductivity of 4.3 mS cm–1 at room temperature. Cyclic voltammetry and DC polarization analysis were carried out to study the stability of solid electrolytes against lithium metal anodes. Interestingly, complex anion:halogen anion-based solid electrolytes exhibited a high critical current density and a long DC cycle stability (>250 cycles).

NanoSpot™ collector for aerosol sample collection for direct microscopy and spectroscopy analysis.

We describe design and characterization of an aerosol NanoSpot™ collector, designed for collection of airborne particles on a microscopy substrate for direct electron and optical microscopy, and laser spectroscopy analysis. The collector implements a water-based, laminar-flow, condensation growth technique, followed by impaction onto an optical/electron microscopy substrate or a transmission electron microscopy grid for direct analysis. The compact design employs three parallel growth tubes allowing a sampling flow rate of 1.2 L min-1. Each growth tube consists of three-temperature regions, for controlling the vapor saturation profile and exit dew point. Following the droplet growth, the three streams merge into one flow and a converging nozzle enhances focusing of grown droplets into a tight beam, prior to their final impaction on the warm surface of the collection substrate. Experiments were conducted for the acquisition of the size-dependent collection efficiency and the aerosol concentration effect on the NanoSpot™ collector. Particles as small as 7 nm were activated and collected on the electron microscopy stub. The collected particle samples were analyzed using electron microscopy and Raman spectroscopy for the acquisition of the particle spatial distribution, the spot sample uniformity, and the analyte concentration. A spot deposit of approximately 0.7-mm diameter is formed for particles over a broad particle diameter range, for effective coupling with microscopic and spectroscopic analysis. Finally, the NanoSpot™ collector's analytical measurement sensitivity for laser Raman analysis and counting statistics for fiber count measurement using optical microscopy were calculated and were compared with those of the conventional aerosol sampling methods.

Geology, geochemistry, fluid inclusions, and H–O–C–S–Pb isotope constraints on the genesis of the Atash-Anbar epithermal gold deposit, Urumieh–Dokhtar magmatic arc, central-northern Iran

The newly discovered Atash-Anbar gold deposit, with ∼2 Mt of ore grading 2.13 g/t Au (locally up to 14 g/t), is located in the Buin-Zahra Range, central-northern Iran. Hosted by Middle Eocene (ca. 39.0 Ma) volcanic-subvolcanic rocks, the Au-polymetallic orebodies occur as NW− and NE − trending quartz-sulfide veins that are structurally controlled by NW-trending faults. The Middle Eocene host rocks are characterized by high-K calc-alkaline, peraluminous signatures, and moderately Eu negative anomalies (Eu/Eu* = 0.2–0.6). Four primary paragenetic stages of veining have been recognized: (I) smoky-grey quartz-chalcopyrite stage, (II) grey-white quartz-polysulfide stage, (III) white-pinkish barite-sulfide stage, and (IV) late quartz-carbonate stage. Fluid inclusion investigations coupled with laser Raman analyses indicate that the ore-forming fluids were formed in a NaCl − H2O ± CO2 system with two types of FIs: two phase, liquid-rich inclusions (type I) and two phase, vapor-rich inclusions (type II). The primary coexisting types I and II inclusions are observed in gold-bearing ore-stage II, sharing similar homogenization temperatures in the range of 233–286 °C and 243–281 °C, but contrasting salinity values of 10.7–14.8 and 14.6–15.5 wt% NaCl equivalent, respectively. Fluid inclusion examinations show that fluid phase separation occurred concurrently with gold precipitation during the ore-stage II. The δ18Ofluid values calculated from the δ18OSMOW and δDSMOW values of the inclusions in quartz veins are 4.9–11.1 ‰ and −84.6 ‰ to −68.3 ‰, respectively. δ13CPDB and δ18OSMOW values of Fe-dolomite are −6.5 ‰ to −5.0 ‰ and 3.1 ‰–4.9 ‰, respectively. H–O–C isotope data indicate magmatic origin of initial ore-forming fluids with minor addition of meteoric water through time. The δ34S values (−3.1 ‰ to −1.2 ‰, avg. = −2.0 ‰) of the ore-stage II sulfides suggest that sulfur comes from a homogeneous magmatic source. The Pb isotopic compositions of sulfides (207Pb/204Pb = 15.420–15.525, 206Pb/204Pb = 18.423–18.536, 208Pb/204Pb = 37.135–38.208) indicate that the Pb in the Atash-Anbar gold deposit is a mixture of crust and mantle components. We conclude that (1) the Atash-Anbar is an IS epithermal system that (2) resulted from Eocene subduction of the NeoTethys Ocean plate beneath the central Iran plate and thus (3) ore-forming fluid and its metal components (i.e., Ag, Pb, and Zn) were emanated through crystallization of the final phase of a granite porphyry intrusion.

Insights into organic metagenesis using Raman spectroscopy and high resolution mass spectrometry: A case study of the Shahezi formation, deep Songliao basin, China

The maturity of sedimentary organic matter is a key parameter for evaluating oil and gas resources. Existing maturity indicators have different evaluation principles and application scopes. This study investigated samples of high to overmature lacustrine source rocks (Ro = 1.33%–4.24%) from the deep Shahezi formation in the Songliao basin, including the zone of catagenesis and metagenesis. Various methods, including vitrinite reflectance, Tmax, laser Raman spectroscopy, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to evaluate the samples' maturity. Through laser Raman analysis of representative samples from the Shahezi formation, most laser Raman parameters showed an inflection point or reversal when the thermal evolution of deep source rocks in the Shahezi formation reaches a certain stage. The variation trend of some Raman parameters and Ro has strong regularity (1.33% < Ro < 3.52%). Based on FT-ICR MS, this research analyzed the relative content and molecular composition of polycyclic and heterocyclic aromatic compounds in soluble organic matter of lake source rock samples and comparison samples (marine shale). Quantitative maturity evaluation of organic matter was performed by converting the signal intensity of each compound. The fitting results of maturity parameter based on FT-ICR MS and Tmax indicated that the maturity parameter of the samples have high coefficient of correlations with maturity in the vitrinite reflectance (Ro) range of 1.33%–2.5% and the Tmax range of 420 °C–600 °C. The maturity parameter values decreased as Ro exceeded 2.5% and Tmax exceeded 600 °C. These findings are attributed to the thermal stability of organic compounds and the formation of pyrobitumen and graphite. The parameters of laser Raman spectroscopy also confirmed the growth of aromatic rings reflected by the maturity parameters of FT-ICR MS. These two methods revealed the structural changes of organic matter in the thermal evolution process from multiple perspectives and provided insights for the maturity evaluation of deep source rocks.

Laser cleaning and Raman analysis of the contamination on the optical window of a rubidium vapor cell

In this work, we present the laser cleaning of a Rubidium vapor cell and the Raman analysis of the contaminant material to be removed. The optical window of the vapor cell had gradually lost transparency due to the development of an opaque layer of unknown composition at the inner side during the normal operation of the cell. Laser cleaning was successfully performed by a frequency-doubled Nd:YAG laser focusing the beam inside the cell, avoiding any possible damage to the window. A single laser pulse was enough to clear away the black discoloration at the focal spot and locally restore the transparency of the window. The Raman spectra of the deposit showed peaks not yet described in the literature. Comparison with known Rubidium germanate spectra and simulation results strongly suggested that the unknown material was Rubidium silicate.

Evaluation of the mineral-promoting effects of in-office bleaching on experimental subsurface enamel lesions

The aim of this study was to investigate the mineral-promoting effects of in-office bleaching agent on enamel subsurface lesions. Enamel subsurface lesions were divided into following groups; D: demineralized samples without any further treatment, DS: samples were further immersed in fresh saliva, DSR: samples were immersed in saliva followed by remineralization buffer, and DSBR: samples were immersed in saliva, subjected to in-office bleaching, and then immersed in remineralization buffer. The control group (CONT) consisted of untreated enamel specimens. Transverse microradiography showed that integrated mineral loss was significantly lower in the DSBR group than in the DSR group. Confocal laser Raman analysis revealed that ν1 phosphate peak height of 959 cm-1 and mineral to matrix ratio of peak heights 959 cm-1 to 1,610 cm-1 in the DSBR group were similar to those in the CONT. In-office bleaching can promote enamel remineralization by altering or removing proteins infiltrated to enamel subsurface lesions.

Hydrothermal evolution and origin of the Suixian molybdenum deposit in the Tongbai orogenic belt, China: Constraints from geology, fluid inclusions and multiple isotopes (H[sbnd]O[sbnd]C[sbnd]S[sbnd]Pb)

The Suixian Mo deposit is a recently discovered deposit in the northern Hubei Province, Tongbai orogen. The Mo orebodies of this deposit are all hosted in the metamorphic rocks (leuco-gneiss, amphibolite and marble) of the Neoproterozoic Tianwangzhai Group, and these orebodies have no direct contact with the granite surrounding the host rocks. The mineralization types are dominated by disseminated ore and fine Mo-bearing quartz-sulfide veins. Hydrothermal alteration consists of abundant feldspathization, epidotization and chloritization, together with less garnetization, tremolitization, and muscovitization. A detailed study on fluid inclusions and multiple isotope (CHOSPb) analyses, together with geologic features, are carried out to investigate the fluid composition, fluid origin and evolution, the source of ore-forming materials, and the ore genetic type. In line with microthermometric measurements and laser Raman analysis on fluid inclusions from three hydrothermal stages, the ore-forming fluid in this deposit is characterized by medium–high temperatures and salinities, as well as richness in CO2 and CH4. Three hydrothermal stages are identified in this deposit, including (I) feldspar-quartz-amphibole-muscovite stage, (II) quartz-sulfides stage, and (III) quartz-calcite-scheelite-fluorite stage. From stages I, II to III, the temperatures change from 290 to 354 °C, through 229–312 °C, to 173–269 °C, with decreasing salinities of 12.6 to 16.3 wt% NaCl equiv., 4.5 to 13.4 wt% NaCl equiv., and 0.2 to 6.9 wt% NaCl equiv., respectively. Most of sulfur isotope data of sulfides (chalcopyrite, pyrite, pyrrhotite and molybdenite) show a narrow δ34S range from −2.0 to 3.0 ‰, suggesting a dominant magmatic source, but some data show either positive or negative values (δ34S: −13.3 to −10.6 ‰ and 9.8 to 11.2 ‰) which may indicate small contribution from the restricted wall rocks. The Pb isotope data (molybdenite, pyrite and pyrrhotite: 206Pb/204Pb: 17.239 to 18.483; 207Pb/204Pb: 15.378 to 15.717; 208Pb/204Pb: 37.889 to 38.850) imply that the lead of sulfides pertains to a mixture of magma (derived from the lower crust) and upper crustal materials (host metamorphic rocks). Based on evident CO2 and CH4 in fluid inclusions, the gradually depleted carbon isotopic compositions (δ13C: −5.4 to −9.9 ‰ at stage I, −14.8 to −19.7 ‰ at stage II, and −17.0 to −24.2 ‰ at stage III) and the HO isotope data, it is suggested that the ore-forming fluids were mainly magmatic fluids with mixture of some organic-containing water, and the thermochemical reaction between the fluids and organic matters (e.g., CH4) from host metamorphic rocks and fluid immiscibility are two important mechanisms for Mo mineralization. Compared with typical Mo deposits in the same orogen, the Suixian Mo deposit belongs to the magmatic hydrothermal vein-type deposit associated with intrusions rather than porphyry or skarn type deposit.

Spectrochemical and stable isotopic characteristics of magnesite deposits in Salem, Southern India: CO2 repository through supergene processes

Magnesite (MgCO3), a carbonate mineral, is considered as a carbon dioxide repository in geological formations and has important industrial applications. Magnesite can form through the alteration of magnesium-rich rocks in marine and non-marine geological settings. We investigated the magnesite deposits of the Salem mafic–ultramafic Complex (SMUC) in southern India through chemical and spectroscopic techniques. We characterize the magnesite mineralization based on visible-near infrared reflectance spectroscopic analyses, XRD, laser Raman analysis, and stable C-O isotope methods. Hyperspectral data show paired absorption at 2.3 and 2.5 µm, attributed to C-O bond vibration overtones and combination tones of C-O stretching and bending. The FTIR spectrum brings out frequencies of vibrations between the atomic bonds. The Laser Raman data show peaks at or near 212, 332, 735, 1096, and 1460 cm−1. The stable isotope data indicate that the magnesite mineralization resulted from the alteration of the ultramafic rocks by low-temperature (49 ± 3.3 °C) fluids. The source of carbon is correlated to the decarboxylation or dissolution of marine limestone. We propose a genetic model that invokes the percolation of meteoric water through weak planes and fractures into the ultramafic rocks.Our results provide a typical example of magnesite as a natural CO2 repository formed through supergene processes.

Optical nonlinear properties of hydroxyapatite based materials

Pure hydroxyapatite (HAP) and biphasic HAP/β-TCP powders were synthesized using wet chemical route. Several heat treatment procedures (900–1300 °C) have been adopted in order to investigate their thermal stability and decomposition. The powder X-ray diffraction studies were carried out to examine the sample’s phase stability. The frequency of vibrations, surface morphology, structural stability, absorption and emission spectra were analyzed using Fourier Transform Infra Red (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Laser Raman analysis, UV-Vis and Fluorescence spectroscopy respectively. The nonlinear optical investigations were explored using Z-Scan (ZS) measurement for all the heat treated samples. The nonlinear (NL) absorption coefficient and nonlinear refractive index of the samples were evaluated using closed and open aperture Z-scan procedures. The observed pattern shows the negative nonlinear refractive index due to the peak followed by a valley. Further, the samples depict saturable absorption and it is also found that the saturable absorption varies as temperature increases. The influence of temperature in the optical nonlinearity of the samples was briefly discussed.

Electrochemical and DFT studies of andrographolide on electrochemically reduced graphene oxide for anti-viral herbaceutical sensor

Herbal extracts are re-emerging as potential remedies for various vector-borne diseases. Amongst several phytochemicals, active ingredients of Andrographis paniculata extract is regarded as promising for dengue fever, caused by Aedes species. However, fingerprinting the active phytochemicals from herbal extracts are often relies on sophisticated analytical techniques which are not universally accessible. Herein, an electrochemically reduced graphene oxide on glassy carbon electrode (ErGO/GCE) has been devised as user-friendly and cost-effective sensor platform for fingerprinting of andrographolide (AG) in anti-dengue polyherbal formulation, i.e., Nilavembu kudineer powder. Confocal laser Raman and X-ray photoelectron spectral analyses revealed that the ErGO surfaces exert structural defects augmenting the conductivity at the electrode interface. DFT investigations enabled that C-3 and C-18 OH groups in AG is involved in the electrooxidation and adsorption-diffusion at the ErGO interface, respectively. Complementary electrochemical studies revealed that the diffusion-controlled process follows 1e−/1H+ transfer. Under optimal experimental conditions, ErGO sensor platform exhibit an amplified current sensitivity of 13.3 μA μM−1. cm−2 in the studied analyte concentration range of 10–400 μM. From the polyherbal extract and clinical sample analysis, the proposed sensor system offers selective, and sensitive detection of target AG regardless of common interferents.