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Marine evaporitic sulfates (gypsum and anhydrite) can record ancient seawater sulfur isotopic data; however, these records are scarce and widely dispersed owing to both restricted environments in which they form and their propensity to be eroded. The late Neoproterozoic–early Cambrian transition was a pivotal timeframe in Earth's history, witnessing the early evolution of animal life and major environmental changes. Seawater chemistry changed abruptly during this interval, including significant changes to the sulfur cycle as evidenced by unusually high sulfur isotopic values. This positive sulfur excursion, termed the Yudomski Event, has been reported previously from early and middle Cambrian units in Siberia, Iran, Australia, and India. In this study, we provide the first report of the Yudomski Event in early and middle Cambrian evaporites from the Tarim Basin, northwestern China. Our data support this event having been of global significance. We additionally report early and middle Ordovician sulfur data from China, which constrain the decline of the Yudomski Event to the late Cambrian. [ABSTRACT FROM AUTHOR]

At the present day, stromatolites are very rare and limited to high-salinity settings. However, abundant and variable stromatolite fossils occur in thick evaporite sequences, the Middle Ordovician Majiagou Formation of the Ordos Basin, northwestern China. The setting and fossil assemblage imply that the high salinity prevented metazoan grazing and allowed stromatolites to flourish. The carbon isotope curve based on new data (average data range from −4.52 to +0.56‰) from drilling cores in Majiagou Formation is in good agreement with Middle Ordovician (Darriwilian), and supports the Middle Ordovician age inferred from biostratigraphy. Sulfur isotopes values (range from +27.1 to +28.0‰) are higher than those of the Upper Ordovician but much lower than those of the Lower Middle Cambrian; thus, the sulfur values imply that the Majiagou Formation is of Middle Ordovician age. New carbon and sulfur isotope data imply that these strata are of Middle Ordovician age, in good agreement with previous paleontological dating. [ABSTRACT FROM AUTHOR]

Abstract The Dongyang gold deposit is a recently discovered large gold deposit located within the Dehua–Youxi–Yongtai mining camp in central–east Fujian Province, southeast China. The deposit contains two individual ore sections: the northwestern Jitou section and the southeastern Dadongkeng section. Most of the mineralization is hosted by rhyolite porphyry and volcanic rocks of the Nanyuan Formation. The locations of subvolcanic intrusions in this area are controlled by NE–SW and NW–SE trending faults that are also closely related to mineralization. Detailed drillhole logging and adit mapping indicates that the deposit contains massive, polymetallic quartz–sulfide veins, and cryptoexplosive breccia type ores. Ore minerals consist of gold, electrum, silver minerals, pyrite, marcasite, and arsenopyrite with lesser amounts of sphalerite and chalcopyrite. The mineralization is hosted by quartz, sericite, illite, chalcedony, and calcite gangue and is associated with sericite and argillic alteration as well as silicification. Fluid inclusion microthermometry indicates that the inclusions within quartz from auriferous quartz–sulfide veins formed during the main stage of mineralization and homogenize at temperatures (T h) of 172 °C–217 °C (average of 192 °C) and have salinities of 0.4–2.6 wt% NaCl equivalent. These low to moderate temperatures and low salinities suggest that the mineralization occurred in an epithermal environment. The precipitation of gold mineralization at Dongyang was most likely caused by the mixing of a large amount of meteoric fluid with a smaller amount of magmatic fluid. Quartz-hosted fluid inclusions have H and O isotope compositions (δD H2O = −63.1 to −54.2‰; δ18O H2O = −5.7‰ to −3.8‰) that are indicative of derivation from a predominantly meteoric source. The S isotope values of pyrite vary from a narrow range of −3.4‰ to 0.9‰, suggesting that the S within the deposit was derived from a homogeneous magmatic source. The mineralization and alteration, gangue and ore mineral assemblages, fluid inclusion and H–O–S isotope compositions indicate that the Dongyang gold deposit is a low-sulfidation epithermal-type deposit. The estimated ore formation depth of Donyang is nearly identical to its actual depth, indicating minor denudation in the region. These results imply a great prospecting potential for other epithermal mineralization at the Dehua–Youxi–Yongtai mining camp. Highlights • The Dongyang gold deposit is a low-sulfidation epithermal gold deposit. • Dominated by a quartz + sericite + illite + schalcedony alteration assemblage. • Mineralization was generated by low- to moderate-temperature and low-salinity fluids. • Stable isotope data indicate that ore-forming fluids were mainly of meteoric origin. • Gold precipitation was caused by mixing of dominant meteoric and minor magmatic fluids. [ABSTRACT FROM AUTHOR]

Abstract The Ancun gold deposit is located in the Dehua–Youxi–Yongtai ore region of Fujian Province, southeast China. The orebodies are mainly hosted in early Paleozoic quartz diorite and structurally controlled alteration zones along NW- and NE-trending faults. Based on the characteristics of mineralization, alteration mineral assemblages, fluid inclusions, and H–O–S isotope data, the Ancun gold deposit can be classified as an intermediate-sulfidation epithermal deposit. The primary metallic minerals are gold, electrum, pyrite, sphalerite, chalcopyrite, and galena, and the principal gangue minerals are quartz, calcite, sericite, and illite. The main types of wall rock alteration include sericitization, argillization, silicification, beresitization, and carbonation. Fluid inclusion studies were carried out on quartz and sphalerite from Au-bearing silicified massive ores and auriferous polymetallic-sulfide-bearing quartz veins from the main ore stage. Microthermometric measurements of fluid inclusions yielded homogenization temperatures (T h) of 152–255 °C and salinities of 0.9–5.3 wt% NaCl equivalent in quartz, and T h of 175–236 °C and salinities of 1.6–5.0 wt% NaCl equivalent in sphalerite. The low to moderate temperatures and salinities imply that the ore-forming fluids formed in epithermal environments. Gold deposition at Ancun is inferred to have been caused mainly by mixing of magmatic and diluted meteoric waters. The H and O isotopic compositions (δD H2O = −76.4‰ to −61.2‰; δ18O H2O = −6.1‰ to 4.0‰) of inclusion water in quartz imply that ore-forming fluids were derived mainly from magmatic sources. Sulfur isotopic values of sulfide minerals vary over a narrow range from −3.9‰ to −0.6‰, suggesting that S was derived from a homogeneous magmatic source. Based on the close temporal and spatial relationship between intermediate-sulfidation epithermal deposits and porphyry deposits, along with the alteration and mineralization characteristics of the Ancun gold deposit, potential exists in this region to drill into deeper-seated porphyry deposits. Highlights • The Ancun gold deposit is an intermediate-sulfidation epithermal gold deposit. • Reliable microthermometry data were obtained for gangue and ore minerals. • Mineralization was formed from low–medium temperature and salinity fluids. • Stable isotope data indicate that ore-forming fluids were mainly of magmatic origin. • Gold deposition was caused by mixing of magmatic and meteoric water. [ABSTRACT FROM AUTHOR]

Abstract The Qiucun gold deposit, located in the central Fujian Province, is one of the most important gold producers at the Dehua prospecting region. The deposit is hosted in the Nanyuan Formation consisting of continental arc volcanic rocks, which belong to the Mesozoic coastal volcanic belt of south China. Gold ore bodies are controlled by a group of NE-NEE trending faults. Wall rock alteration shows that gold mineralization is closely associated with quartz (chalcedony)-illite-pyrite-calcite assemblages, in which pyrite is the dominate sulfides (>90%). Petrographic study of ore minerals shows that gold occurs as electrum grains of 2–65 μm in diameter, interstitially or in fractures within pyrite. EPMA analysis of electrum yielded compositions of 62–69 wt% Au and 28–33 wt% Ag. Fluid inclusions petrographic and microthermometric studies were carried out on auriferous quartz veins from three different elevations, i.e. 712 m, 742 m and 820 m above sea level. Two types of fluid inclusion were observed, namely two-phase liquid-rich (type I) and two-phase vapor-rich (type II) fluid inclusions. There inclusions are predominately aqueous inclusions but can sometimes contain minor CO 2 and N 2 as revealed by laser Raman analysis. Type I inclusions show homogenization temperatures (Th) of 181–248 °C, with salinities of 0.5–2.6 wt% NaCl equivalent. Type II inclusions display Th of 208–249 °C, with salinities of 0.5–0.9 wt% NaCl equivalent. The occurrence of platy calcite and hydrothermal breccias, together with coexisting type I and type II inclusions which shows similar homogenization temperatures but contrasting salinities, all indicate that fluid boiling is a crucial mechanism for ore deposition at the Qiucun gold deposit. Combining the geological settings, alteration, mineralization and fluid inclusion characteristics, we propose that the Qiucun gold deposit is a low-sulfidation epithermal deposit. The estimated pressure calculated by fluid inclusion boiling assemblages corresponds to a formation depth of 200 to 260 m below paleo-surface, which is slightly deeper than the current depth. Accordingly, the denudation thickness of the overlying Nanyuan volcanic rocks is supposed to be approximately 100 m since ore deposition, which is conductive to the preservation of epithermal ore deposit. It is therefore suggested that the large area of the Daiyunshan Volcanic Basin at Dehua district is of great potential for epithermal ore exploration. Highlights • A low-sulfidation genesis was proposed to the Qiucun gold deposit. • Fluid boiling induced metal precipitation from hydrothermal solutions. • Denudation thickness of deposit was estimated to be 100 m since formation. • Dehua prospecting region shows great potential for epithermal deposit exploration. [ABSTRACT FROM AUTHOR]

[Display omitted] • The oscillatory zonation exhibits distinct trace element patterns in contrast to the sector zonation. • For in situ studies, it is advisable to analyze cassiterite samples that retain their intact crystal texture. • The two trends observed in the Fe–W diagram of cassiterite associated with granite were elucidated. Cathodoluminescent (CL) imaging, combined quantitative geochemical analyses using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), was employed to study the cassiterite crystals from the Yunling tin deposit in western Yunnan Province, China. This investigation aimed to establish a connection between CL response with trace element compositions. The CL imaging of a well-formed centimeter-scale euhedral single crystal of cassiterite revealed two types of primary growth domains, namely oscillatory and sector zoning. High spatial resolution LA-ICP-MS spot analysis along three centimeter-scale profiles revealed that the oscillatory zoning patterns were primarily defined by the concentrations of Nb and Ta. The CL response associated with the oscillatory zoning was attributed to the interplay between activators such as Ti, Nb, Ta, and V, and quenchers like Fe. On the other hand, sector zoning exhibited significantly high W content, reaching three orders of magnitude greater than that in the oscillatory zoning. Consequently, the sectors displayed a dark CL response. Furthermore, U showed a sectoral preference, with contents within the sector zoning examined in this study reaching up to 10 ppm. The systematic variations in geochemical compositions suggest that the incorporation of trace elements in Yunling cassiterite involves a coupled substitutional mechanism of pentavalent and trivalent elements (e.g., Sc3+ + V5+ ↔ 2Sn4+) with H+ potentially serving as a compensating ion for the Fe3+ excess. It is worth noting that the trace element enrichment and potential substitution in the sector and non-sector regions of the single crystal may differ significantly. Therefore, the use of cassiterite trace elements as indicators of the mineralization environment requires careful consideration, particularly when analyzing randomly selected particles obtained from crushing. In such instances, it is recommended to utilize cassiterite samples that exhibit a preserved crystal texture extending from the core to the rim, such as cassiterite in thin sections or morphology-integral cassiterite separates. Moreover, the contrasting W contents observed between the sector and non-sector zones may provide an explanation for two trends in the Fe–W diagram of cassiterite associated with granite that were previously-unspecified. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wolframite-quartz veins and scheelite-skarn can be traced back to an identical magmatic fluid source. • Formation of diverse W mineralization styles is mainly controlled by different host lithology and fluid processes. • Fluid-rock interaction may have played an important role in wolframite deposition than fluid immiscibility at Yaogangxian. • Ca responsible for the precipitation of scheelite is primarily contributed by carbonate. The large-scale Yaogangxian W deposit, located in central of the Nanling metallogenic belt, South China, comprises independent quartz vein-type and skarn-type W mineralization. Wolframite-bearing quartz veins occur invariably in metasandstone and slate to the northwest of the Yaogangxian granitic intrusion, whereas scheelite-skarn are mainly hosted by the limestone to the east. The vertical extension of single wolframite-bearing quartz vein can reach up to 1000 m and we focused on the vein samples collected from the deepest level (26 level) which likely recorded early magmatic fluids. For skarn mineralization, two scheelite precipitation stages were recognized, namely scheelite-1 in retrograde stage and scheelite-2 from sulfide-stage. To reveal the fluid sources and characteristics of two mineralizing systems, detailed petrography and microthermometry analyses were carried out on fluid inclusion assemblages (FIA) in scheelite, wolframite and their coexisting quartz. Fluid compositions were obtained from individual fluid inclusion (FI) in ore and gangue minerals via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. These data aid elucidation on the source and nature of fluids in the two distinct W mineralization styles. The chemical compositions of FIs hosted in wolframite and scheelite points to a common magmatic source. The fluid in the scheelite ore section exhibits lower As and B than the wolframite ore section, indicating that boiling may have occurred at early skarn stage. Fluid evolution in the two mineralizing systems suggest that formation of diverse W mineralization styles is mainly controlled by different host lithology and fluid processes. In the wolframite ore section, ore-forming fluid recorded in the deepest level of vein show elevated As, B, K and Rb contents than previously reported ore-forming fluid obtained from the tip of the vein. This likely indicate absence of intensive fluid immiscibility in the deep during wolframite formation, which may rather be accompanied by fluid-rock interaction. In the scheelite ore section, constant injection of meteoric water is revealed. FI hosted in scheelite-1 and 2 exhibit similar compositions, and the lower K content in scheelite-2 fluid is thought to be caused by sericitization in the retrograde stage skarn. The Mo content of scheelite decreased from the retrograde stage to sulfide-stage, indicating a decrease in oxygen fugacity. Based on these conclusion and previous geological and geochronological studies, we propose a metallogenic model of the coupled wolframite-quartz vein and scheelite-skarn mineralization. [ABSTRACT FROM AUTHOR]