scholarly journals In situ geochemical characterization of pyrite crystals in burial dolomites of St. George Group carbonates

2018 ◽  
Vol 55 (5) ◽  
pp. 536-544 ◽  
Author(s):  
Babatunde John Olanipekun ◽  
Karem Azmy
Keyword(s):  
Sulfate Reduction ◽  
Fluid Inclusions ◽  
Secondary Ion Mass Spectrometry ◽  
Main Stage ◽  
Mississippi Valley ◽  
Sulfide Mineralization ◽  
Two Phase ◽  
Saddle Dolomite ◽  
Phase Fluid

Secondary ion mass spectrometry (SIMS) was used to measure the δ34S of pyrite disseminated in burial dolomite matrix of Boat Harbour formation at Main Brook and Daniel’s Harbour (about 130 km apart). At Main Brook, δ34S values for the pyrite grains show wide variation (–15 to +20‰ (n = 20)), but are mostly negative. Combined with a paucity of two-phase fluid inclusions in the host burial dolomite, the depleted δ34S values suggest that the pyrite is a direct product of bacterial sulfate reduction (BSR). Predominantly negative δ34S values were also obtained for sampled pyrite at Daniel’s Harbour and Port au Choix; however, relatively high homogenization temperatures (>100 °C) of two-phase fluid inclusions in the host dolomite is incompatible with a BSR process for pyrite formation. More so, Daniel’s Harbour is a site for main stage sulfide mineralization (Mississippi Valley-type (MVT) system), hosted in similarly burial dolomite and that has been previously constrained to be associated with thermochemical sulfate reduction (TSR). A relative proximity of the currently studied pyrite samples to this MVT system deposit is thus inconsistent with an in-situ BSR for these pyrites. The analyzed pyrite grains are commonly encased in bitumen, and they postdate their host burial dolomite and predate deep burial saddle dolomite. Taken together, the depleted δ34S signature in the pyrite was likely inherited from migrated hydrocarbons in the reservoir. Incursion of an initial pulse of hot sulfate-rich brine into the formation can cause thermal cracking of hydrocarbons, thereby releasing its low δ34S. Thus the inherited low δ34S signature was likely a product of an earlier BSR that occurred in the kerogen or source organic materials in source rock. Subsequently, the main stage sulfide mineralization (MVT deposit) occurred via in-situ TSR. These findings have an implication for the paragenetic history of sulfide minerals precipitated during MVT mineralization episode.

scholarly journals Microbial sulfate reduction plays an important role at the initial stage of subseafloor sulfide mineralization

Geology ◽  
2020 ◽  
Author(s):  
Tatsuo Nozaki ◽  
Toshiro Nagase ◽  
Takayuki Ushikubo ◽  
Kenji Shimizu ◽  
Jun-ichiro Ishibashi ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Secondary Ion Mass Spectrometry ◽  
Okinawa Trough ◽  
Sulfide Minerals ◽  
Sulfide Mineralization ◽  
Ambient Seawater ◽  
Microbial Sulfate Reduction ◽  
Framboidal Pyrite ◽  
Initial Stage ◽  
Iheya North Knoll

Seafloor hydrothermal deposits form when hydrothermal fluid mixes with ambient seawater, and constituent sulfide minerals are usually interpreted to precipitate abiogenically. Recent research drilling at Izena Hole and Iheya North Knoll in the middle Okinawa Trough (East China Sea), combined with secondary ion mass spectrometry determinations of δ34S in pyrite grains, provides compelling evidence that the initial stage of subseafloor sulfide mineralization is closely associated with microbial sulfate reduction. During the sulfide maturation process, pyrite textures progress from framboidal to colloform to euhedral. Pyrite δ34S has highly negative values (as low as –38.9‰) in framboidal pyrite, which systematically increase toward positive values in colloform and euhedral pyrite. Sulfur isotope fractionation between seawater sulfate (+21.2‰) and framboidal pyrite (–38.9‰) is as great as –60‰, which can be attained only by microbial sulfate reduction in an open system. Because framboidal pyrite is commonly replaced by chalcopyrite, galena, and sphalerite, framboidal pyrite appears to function as the starting material (nucleus) of other sulfide minerals. We conclude that framboidal pyrite, containing microbially reduced sulfur, plays an important role at the initial stage of subseafloor sulfide mineralization.

Origin of the Fule Pb–Zn deposit, Yunnan Province, SW China: insight from in situ S isotope analysis by NanoSIMS

2019 ◽  
Vol 157 (3) ◽  
pp. 393-404 ◽  
Author(s):  
Zhenli Li ◽  
Lin Ye ◽  
Yusi Hu ◽  
Zhilong Huang ◽  
Chen Wei ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Isotope Analysis ◽  
Isotopic Analysis ◽  
Mississippi Valley ◽  
Metallogenic Province ◽  
Sulphide Precipitation ◽  
Isotope Studies ◽  
Secondary Ion ◽  
S Isotope

AbstractThe Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province is one of the most productive areas of Pb–Zn resources in China. The Fule deposit occurs in Permian carbonate and contains Pb–Zn reserves exceeding 1 Mt. To investigate the sulphur source, in situ S isotopic analysis of sphalerite and pyrite was carried out using nanoscale secondary-ion mass spectrometry. The results show that the δ34S values of the sulphide minerals range from +16.1‰ to +23.0‰, higher than that of marine sulphates hosted in Permian carbonate rocks (+11‰), but similar to that of sulphates over a broader area (+12.9‰ to +25.9‰). The sulphates in the regional rocks could therefore represent an important source of S for the Fule deposit via thermochemical sulphate reduction. The S source of the Fule deposit is different from those of most other Pb–Zn deposits in the SYG Pb–Zn mineralization province, which were mainly derived from the ore-bearing strata. The δ34S values of the early to late generations and some single sulphide crystals from the cores to rims show a slight increasing trend, implying that partial Rayleigh fractionation took place in the Fule deposit. It is suggested that the Fule sulphide precipitation resulted from the mixing of a metalliferous fluid with a H2S-rich fluid derived from the regional strata. Combining the geology, mineralogy and S isotope results with previous Pb isotope studies, it is suggested that the Fule deposit should be attributed to a Mississippi Valley type deposit.

New insights into the evolution of Mississippi Valley-Type hydrothermal system: A case study of the Wusihe Pb-Zn deposit, South China, using quartz in-situ trace elements and sulfides in situ S-Pb isotopes

2020 ◽  
Vol 105 (1) ◽  
pp. 35-51 ◽  
Author(s):  
Kai Luo ◽  
Jia-Xi Zhou ◽  
Zhi-Long Huang ◽  
John Caulfield ◽  
Jian-Xin Zhao ◽  
...  
Keyword(s):  
Trace Elements ◽  
Sulfate Reduction ◽  
South China ◽  
Hydrothermal System ◽  
Stage Ii ◽  
Pb Isotopes ◽  
Mississippi Valley ◽  
Mississippi Valley Type

Abstract Unraveling the evolution of Mississippi Valley-type (MVT) hydrothermal system is crucial for understanding ore genesis and exploration. In this paper, we take the Wusihe Pb-Zn deposit in the western Yangtze Block (South China) as a case study, using detailed ore deposit geology, quartz in situ trace elements, and sulfides in situ S-Pb isotopes, to propose a new integrated model for the evolution of MVT hydrothermal system. Four hydrothermal stages were identified in the Wusihe ore district: (I) lamellar pyrite-sphalerite; (II) disseminated, stock-work, and brecciated sphalerite-galena; (III) massive galena, and (IV) veined calcite-bitumen. Within the most representative stage (stage II), Al concentrations in quartz (Q) increase from 8.46–354 ppm (mean 134 ppm) of Q1 to 171–3049 ppm (mean 1062 ppm) of Q2, and then decrease to 3.18–149 ppm (mean 25.4 ppm) of Q3. This trend indicates the role of acid-producing processes that resulted from sulfide precipitation and acid consumption by carbonate buffering. The occurrence of authigenic non-altered K-feldspar provides further evidence that the ore-forming fluids were weakly acidic with pH values of > ~5.5. Moreover, new bulk δ34S values of sulfides (+1.8 to +14.3‰) are overall lower than those previously reported (+7.1 to +20.9‰), implying that in addition to thermochemical sulfate reduction (TSR), bacterial sulfate reduction (BSR) may play an important role in the formation of S2–. In situ δ34S values show a larger range (–4.3 to +26.6‰), and significantly, varies within single grains (up to +12.3‰), suggesting mixing of two isotopically distinct S2– end-members produced by TSR and BSR. The diagenetic and hydrothermal early phase (stage I) sulfides were formed within a nearly closed system of BSR, whereas the formation of late phase (stage II and stage III) sulfides was caused by the input of hydrothermal fluids that promoted TSR. New galena in situ Pb isotopic ratios (206Pb/204Pb = 18.02–18.19, 207Pb/204Pb = 15.66–15.69, and 208Pb/204Pb = 38.14–38.39) suggest that the sources of mineralizing metals in the Wusihe deposit are mainly Proterozoic basement rocks. Hence, a multi-process model (i.e., basin-mountain coupling, fluid mixing, local sulfate reduction, in situ acid-producing and involvement of black shales and carbonate sequences) was responsible for the formation of the Wusihe deposit, while S2– was produced by both TSR and BSR, providing new insights into the evolution of MVT hydrothermal system.

scholarly journals Origin of the Moroccan Touissit-Bou Beker and Jbel Bou Dahar Supergene Non-Sulfide Biomineralization and its Relevance to Microbiological Activity, Late Miocene Uplift and Climate Changes

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 401
Author(s):  
Mohammed Bouabdellah ◽  
Wissale Boukirou ◽  
Adriana Potra ◽  
Erik Melchiorre ◽  
Hassan Bouzahzah ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Climatic Conditions ◽  
Current Data ◽  
Ore Deposits ◽  
Main Stage ◽  
Mississippi Valley ◽  
Sulfide Mineralization ◽  
Two Stages ◽  
Mississippi Valley Type ◽  
Valley Type

Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type districts of the Moroccan Atlasic system have been investigated in order to gain insights into the origin and processes that contributed to the formation of the base metal non-sulfide mineralization. In both districts, direct replacement (“red calamine”) and wallrock replacement (“white calamine”) ores are observed. Based on the mineral assemblages, ore textures, and crosscutting relations, three distinct mineralizing stages are recognized. The earliest, pre-non-sulfide gossanous stage was a prerequisite for the following supergene stages and constituted the driving force that ultimately promoted the leaching of most base metals such as Zn and Cu and alkalis from their rock sources. The following two stages, referred to as the main supergene “red calamine” and late “white calamine” ore stages, generated the bulk of mineable “calamine” ores in the Touissit-Bou Beker and Jbel Bou Dahar districts. Stable isotope compositions (d13CV-PDB, d18OV-SMOW, d34SCDT) support a three-stage model whereby metals were released by supergene acidic fluids and then precipitated by bacteria and archaea-mediated metal-rich meteoric fluids due to a decrease in temperature and/or increase of fO2. Oxygen isotope thermometry indicates decreasing precipitation temperatures with advancing paragenetic sequence from 33° to 18 °C, with wet to semi-arid to arid climatic conditions. The close spatial relationships between coexisting sulfide and non-sulfide mineralization along with stable isotope constraints suggest that the oxidation of sulfides occurred concurrently after the main stage of the Alpine orogeny between 15 Ma and the present. More importantly, the current data show for the first time the involvement of biologically controlled activity as the major driving process that triggered both oxidation and deposition of supergene mineralization at Jbel Bou Dahar and Touissit-Bou Beker districts. Conclusions drawn from this study therefore have implications for supergene Mississippi Valley-type (MVT) -derived non-sulfide deposits worldwide and account for the prominent role of biological processes in the genesis of this category of ore deposits.

CONSERVATION OF RARE SPECIES PLANTS AND LICHENS IN SITU WITH PLANNED ANTHROPOGENIC ACTIVITIES: BASIC APPROACHES AND IMPLEMENTATION PRINCIPLES

2018 ◽  
Vol 12 (7-8) ◽  
pp. 38-45
Author(s):  
A. N. EFREMOV ◽  
N. V. PLIKINA ◽  
T. ABELI
Keyword(s):  
Rare Species ◽  
Technology Implementation ◽  
Technology Development ◽  
Anthropogenic Activities ◽  
Natural Habitat ◽  
Local Population ◽  
Main Stage ◽  
Social Risks

Rare species are most vulnerable to man-made impacts, due to their biological characteristics or natural resource management. As a rule, the economic impact is associated with the destruction and damage of individual organisms, the destruction or alienation of habitats. Unfortunately, the conservation of habitat integrity is an important protection strategy, which is not always achievable in the implementation of industrial and infrastructural projects. The aim of the publication is to summarize the experience in the field of protection of rare species in the natural habitat (in situ), to evaluate and analyze the possibility of using existing methods in design and survey activities. In this regard, the main methodological approaches to the protection of rare species in the natural habitat (in situ) during the proposed economic activity were reflected. The algorithm suggested by the authors for implementing the in situ project should include a preparatory stage (initial data collection, preliminary risk assessments, technology development, obtaining permitting documentation), the main stage, the content of which is determined by the selected technology and a long monitoring stage, which makes it possible to assess the effectiveness of the taken measures. Among the main risks of in situ technology implementation, the following can be noted: the limited resources of the population that do not allow for the implementation of the procedure without prior reproduction of individuals in situ (in vitro); limited knowledge of the biology of the species; the possibility of invasion; the possibility of crossing for closely related species that сo-exist in the same habitat; social risks and consequences, target species or population may be important for the local population; financial risks during the recovery of the population. The available experience makes it possible to consider the approach to the conservation of rare species in situ as the best available technology that contributes to reducing negative environmental risks.

Optics-Free Visualization of Proteins in Single Cells by Time of Flight-Secondary Ion Mass Spectrometry Coupled with Genetically Encoded Chemical Tags

2020 ◽  
Author(s):  
Feifei Jia ◽  
Jie Wang ◽  
Yanyan Zhang ◽  
Qun Luo ◽  
Luyu Qi ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Single Cells ◽  
Time Of Flight ◽  
E Coli ◽  
Tof Sims ◽  
Ion Mass Spectrometry ◽  
Chemical Tags ◽  
Secondary Ion

<p></p><p><i>In situ</i> visualization of proteins of interest at single cell level is attractive in cell biology, molecular biology and biomedicine, which usually involves photon, electron or X-ray based imaging methods. Herein, we report an optics-free strategy that images a specific protein in single cells by time of flight-secondary ion mass spectrometry (ToF-SIMS) following genetic incorporation of fluorine-containing unnatural amino acids as a chemical tag into the protein via genetic code expansion technique. The method was developed and validated by imaging GFP in E. coli and human HeLa cancer cells, and then utilized to visualize the distribution of chemotaxis protein CheA in E. coli cells and the interaction between high mobility group box 1 protein and cisplatin damaged DNA in HeLa cells. The present work highlights the power of ToF-SIMS imaging combined with genetically encoded chemical tags for <i>in situ </i>visualization of proteins of interest as well as the interactions between proteins and drugs or drug damaged DNA in single cells.</p><p></p>

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