Abstract Carlin-type Au deposits in Guizhou Province, China, have similarities to and differences from the Carlin-type Au deposits in Nevada, USA. The Shuiyindong and Jinfeng deposits, located in the Guizhou Province of southern China, are compared with the Getchell and Cortez Hills Carlin-type Au deposits of Nevada in terms of ore paragenesis and pyrite chemistry. The Guizhou deposits formed in a tectonic setting similar to Nevada with the deposition of passive-margin sequences in a rifted cratonic margin context with subsequent deformation. In both districts, orebodies are preferentially hosted in limestone and calcareous siltstone and are related to faults, gold is invisible and ionically bound in arsenian pyrite, and ore-stage minerals include quartz and illite with late ore-stage minerals, including calcite, realgar, orpiment, and stibnite. Despite major similarities, however, the Guizhou deposits have characteristics that contrast with those of Carlin-type deposits of Nevada. Significant differences include the following: Guizhou ore-stage pyrite is commonly subhedral to euhedral, and typical Nevada fuzzy ore pyrite is absent. Guizhou ore pyrite contains significantly less Au, As, Hg, Tl, Cu, and Sb than the Nevada ore pyrite. Decarbonatization in Nevada deposits is expressed by extensive removal of calcite, dolomite, and Fe dolomite. In contrast, decarbonatization in the Guizhou deposits results in loss of most primary calcite, but Fe dolomite was instead sulfidized, forming ore pyrite and dolomite. This alteration is a key process in the formation of ore pyrite in the Guizhou deposits. Silicification in Nevada deposits is characterized by jasperoid replacement of calcite, dolomite, and Fe dolomite, whereas in the Guizhou deposits jasperoid replaced mainly calcite but not Fe dolomite or dolomite. Minor vein quartz, which formed during the early ore stage in Guizhou deposits, has not been identified in Nevada deposits. Clay alteration in the Nevada deposits is characterized by formation of significant illite and variable kaolinite/dickite; however, in the Guizhou deposits, trace to minor illite is present and kaolinite is uncommon. Late ore-stage arsenopyrite and vein quartz are common in Guizhou deposit but are rare in Nevada deposits. Guizhou ore fluids contained significantly more CO 2 and were higher in temperature and pressure compared with the ore fluids in Nevada deposits. To date, magmatism spatially or temporally associated with the Guizhou deposits has not been recognized. Conversely, the Nevada deposits coincide in time and space with the southward sweep of Eocene magmatism and related extension. Dolomite-stable alteration in Guizhou formed from less acidic, CO 2 -rich ore fluids at higher temperature and pressure compared with Nevada deposits, reflecting similarities between Guizhou deposits and orogenic systems. Study results are consistent with Guizhou deposits having formed in a transitional setting between typical orogenic gold and shallow Carlin-type deposits, as indicated by estimated pressure-temperature conditions at the time of gold deposition and ore-forming fluid chemistry.

Abstract The Dian-Qian-Gui “Golden Triangle” area of southwest China has the second-largest concentration of Carlin-type gold deposits in the world, containing more than 800 tonnes of Au (25.7 Moz). All of the deposits are located along long-lived, deep-penetrating crustal structures inherited from Devonian rifting of the Precambrian Yangtze craton. They are hosted in Cambrian to Middle Triassic platform carbonate, transitional, and siliciclastic rocks of the Youjiang basin, and locally in Late Permian diabase intrusions or volcaniclastic rocks. These deposits have many characteristics in common with Carlin-type gold deposits in Nevada, USA, including lithology of host rocks, alteration types, elemental associations, and occurrence of gold. Our recent work has identified two episodes of gold mineralization in the Dian-Qian-Gui area that have distinct geologic settings, radiogenic and stable isotopes, and fluid inclusions. Gold deposits hosted in diabase intrusions along the southern margin of the Youjiang basin formed in the Middle-Late Triassic (232–212 Ma) and have low-salinity (~2 wt % NaCl equiv), high-temperature (~245°C) fluid inclusions with high-density CO 2 that are similar to those in orogenic gold deposits. Sediment-hosted gold deposits along the northern margin of the Youjiang basin formed in the Late Jurassic-Early Cretaceous (148–134 Ma) and have moderate salinity (~5 wt % NaCl equiv) and temperature (~210°C) fluid inclusions, with variable CO 2 , low Fe, and high As, Sb, and Au contents, based on microanalysis of fluid inclusions. Deposits on each margin contain gold-bearing arsenian pyrite and arsenopyrite that precipitated from H 2 S-rich fluids by sulfidation of Fe minerals in the host rocks. Oxygen and hydrogen isotopes indicate metamorphic fluid sources for deposits on both margins, but sulfur isotopes indicate different sources of reduced sulfur. The narrow range of high δ 34 S values for arsenian pyrite and arsenopyrite from districts along the southern margin of the Youjiang basin suggests derivation from a sedimentary source. Some of the deposits along the northern margin of the Youjiang basin have δ 34 S values near zero that permit a magmatic or sedimentary sulfur source, while others have high values indicative of a sedimentary source. We propose a model in which metamorphic ore fluids were generated by regional metamorphism of sedimentary rocks during the Indosinian orogeny along the southern margin and the Yanshanian orogeny along the northern margin of the Youjiang basin. Metamorphic ore fluids were focused into reactivated basement-penetrating rift faults and flowed upward into structural highs in response to stress relaxation during each orogeny. Gold-bearing sulfides precipitated where the ore fluids reacted with carbonaceous and Fe-rich host rocks and mixed with variably exchanged meteoric ground water. The pressure-temperature conditions and compositions of ore fluids are intermediate between those of the mesozonal orogenic and the shallow Carlin-type gold systems. The Chinese Carlin-type gold deposits may, therefore, represent a link between orogenic and Carlin-type gold deposits that formed during transitions between compressional and extensional environments.