Separation of Au and Sb mineralization from different hydrothermal stages is a common phenomenon in many Au-Sb deposits, but its cause remains enigmatic. The Qukulekedong intrusion-related Au-Sb deposit in the East Kunlun Orogen has undergone four hydrothermal stages: (1) barren quartz vein, (2) quartz vein with disseminated arsenopyrite-pyrite alteration halo, (3) stibnite-quartz +/- native gold vein, and (4) calcite-quartz vein. Stages 2 and 3 formed disseminated Au and vein-type Sb +/- Au ore, respectively. Here, internal texture and trace elements in quartz, fluid inclusions (Fls) microthermometry, and H-O isotopes were analyzed to unravel the separation mechanism of the Au and Sb +/- Au mineralization at Qukulekedong. Stage 2 quartz has euhedral growth zones with elevated Ti-Al-Li-K-Sb and varying As contents. Stage 2 FIs have medium homogenization temperature (203-307 degrees C) and salinity (12.2-17.8 wt% NaCl equiv.), and are CH4-rich. They have delta 18OH2O = 9.5-10.8 %o and delta DH2O =-93.4 to-80.8 %o. In contrast, stage 3 quartz has lower Ti-Al-Li-K and varying Sb contents. Stage 3 FIs show phase separation (coexistence of V-, L-and V-L-type FIs), and are of lower temperature (141-164 degrees C) and salinity (2.1-10.7 wt% NaCl equiv.), and CO2- and CH4-bearing. They have delta 18OH2O = 3.3-5.2 %o and delta DH2O = -95.4 to -89.6 %o. Considering that the disseminated Au ore is Sb-rich and its pyrite has fine stibnite inclusions, we suggest that the disseminated Au and vein-type Sb +/- Au mineralization shared a common Au-and Sb-rich initial magmatic fluids. The disseminated Au mineralization may have formed by fluid-rock interactions. Meanwhile, the vein-type Sb +/- Au mineralization was likely caused by the phase separation and cooling led by dilational activities and meteoric water injection.

Genetic classification of sediment-hosted Au deposits is often disputed in many orogenic belts around the world. The marine sediment-hosted Qukuleke Au deposit (>5 t Au) is an example of this, which has been attributed to orogenic or intrusion-related type. This paper addresses its metallogeny through detailed geologic and petrographic studies, together with apatite U-Pb dating and C-O-S-Pb isotopes. The hydrothermal paragenesis at Qukuleke is divided into three stages (I to III): Stage I (pre-ore) sheeted quartz veins; Stage II (main ore) pervasive sericite +/- carbonate +/- apatite +/- pyrite +/- arsenopyrite alteration associated with quartz-calcite +/- stibnite veins; Stage III (post-ore) barren calcite veins. LA-ICP-MS hydrothermal apatite U-Pb dating on Stage II disseminated Au ore yielded 208.1 +/- 6.5 Ma, coeval with the Late Triassic post-collisional intrusions from the periphery of Qukuleke deposit. Carbon-oxygen isotopes of Au-Sb ore-related hydrothermal calcite show that the hydrothermal fluids were derived from the marine carbonate ore host with considerable magmatic input. Lead-sulfur isotopes of the Au-Sb ore-related are consistent with those of coeval intrusions around the deposit, but different from those of the local sedimentary strata. Our age and geochemical data suggest the presence of a magma source that supplied the hydrothermal fluids, sulfur and metals for the mineralization. Combining the low sulfide content and the Au-As-W-Sb-Mo assemblage characteristics, the Qukuleke is best classified as a sediment-hosted intrusion-related Au deposit. Considering also the discovery of the large coeval Qukukekedong Au deposit nearby, we propose that Late Triassic intrusion-related Au system is a high-potential exploration target in the western EKOB.

The large intrusion-related Qukulekedong Au-Sb deposit was recently discovered in the East Kunlun Orogenic Belt (EKOB). Mineralization occurs in the Late Triassic granitoid intrusion and its surrounding carbonaceous siltstone. Pyrite is an important Au-rich mineral in the deposit, and can be classified into three types: Py1, Py2 and Py3. The lattermost Py3 represents the main metallogenic episode. In-situ trace elements and S-Pb isotopes of pyrites indicate that the Py3 has a relatively high Au content (mean 7.84 ppm), high Co/Ni ratios (mean 4.93), with d34S values around 0 & PTSTHOUSND; (-2.03 to 1.69 & PTSTHOUSND;) and matched Pb isotopic ratios to the intrusions, suggesting that Au and other ore-forming material were most likely derived from a magmatic source. Carbonaceous siltstone contains organic carbon up to 3.39 wt%. According to the evidence of paragenetic minerals, texture, and S isotopes, the carbonaceous material may have played a key role in the precipitation of Au and pyrite in the carbonaceous strata. The Au-As decoupling of pyrite in intrusions may be attributed to the Au precipitation and crystallization of arsenopyrite, which was caused by the decreasing of oxygen fugacity. Overall, the new understanding highlights the importance of carbonaceous strata in intrusion-related Au ore-forming processes, the combination of carbonaceous strata and Late Triassic intrusions provides a new exploration direction for Au prospecting in the EKOB and similar settings.& COPY; 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Numerous Paleozoic deposits have been found in the Tianshan Mountains. Postmineralization burial plays an important role in the preservation of Paleozoic epizonal deposits. However, the preservation mechanisms for mesozonal deposits in the Tianshan Mountains need further investigation. The late Paleozoic Katebasu gold-copper deposit (with a reported mineralization age varying from - 270 Ma to - 330 Ma) in the Chinese Western Tianshan is a mesothermal magmatic hydrothermal deposit that formed at mesozonal depths. The exhumation process and preservation mechanisms of this deposit remain ambiguous. In this study, (U-Th)/He and fission-track dating were applied to samples from a vertical profile to constrain the exhumation history of the Katebasu deposit. Apatite (U-Th)/He and fission-track ages vary systematically with elevation, ranging from 32.4 +/- 9.0 Ma to 176.4 +/- 18.0 Ma and 106.4 +/- 3.1 Ma to 181.7 +/- 5.1 Ma, respectively. Zircon (U-Th)/He ages range from 220.4 +/- 11.0 Ma to 260.1 +/- 17.4 Ma. The age-elevation relationship and inverse thermal modeling reveal that the Katebasu deposit underwent two phases of exhumation. The first phase of exhumation, which caused at least 4 km of erosion, occurred during the late Paleozoic to Early Jurassic. The second exhumation started during the Early Oligocene, resulting in - 0.9 km of erosion. A protracted period of tectonic stability during the middle-late Mesozoic to early Cenozoic and limited exhumation during the late Cenozoic uplift played important roles in the preservation of the Katebasu deposit.

The Qukulekedong deposit is a recently discovered large Au-Sb deposit in the western part of the East Kunlun Orogenic Belt, NW China. Pyrite with a characteristic dissolution-regrowth texture has developed in the high-grade Au ore of the deposit. In this study, information on the mineralogical properties, elements distribution, and in situ S isotopic composition of the dissolution-regrowth pyrite was used to interpret its genesis and relationship to Au concentration. The pyrite grains are composed of a core, mantle, and rim. The core consists of pyrite with delta 34S values ranging from 1.02 %o to 1.99 %o, indicating a neutral pH, medium-oxygen fugacity environment. The mantle consists of sphalerite, sericite, quartz, and ankerite with dissolution texture, indicating pyrite dissolution and replacement in a neutral pH, high-oxygen fugacity environment. The rim consists of pyrite with fine arsenopyrite inclusions and recovers the crystal shape of the pyrite, which have delta 34S values ranging from 1.60 %o to 2.67 %o. This indicates that the rim was formed via regrowth in a neutral pH, low-oxygen fugacity environment. The dissolution of the mantle and regrowth of the rim represent an oxygen fugacity increa-sing-decreasing process in the formation of pyrite. The increase in oxygen fugacity could remobilize Au from dissolved pyrite, forming a highly Au-concentrated hydrothermal fluid. The decrease in oxygen fugacity trig-gered the supersaturation and precipitation of Au, forming an Au-rich rim. Combining geological characteristics, the pyrite likely had a magmatic sulfur origin and formed via a dissolution-regrowth process caused by the depressurization-oxidation associated with rock fractures. The dissolution-regrowth pyrite can be used as a mineralogical indicator for regional Au exploration.

The Qukulekedong Au-Sb deposit is the first large Au-Sb deposit discovered in the western section of the East Kunlun Orogenic Belt. Even though the significance of the deposit is important, mineralization timing and genesis of the deposit have remained elusive. This study integrated a regional geological survey and the analysis of deposit characteristics with newly acquired geochemical data (Re-Os dating, LA-ICP-MS zircon U-Pb dating, and Lu-Hf isotopes) to gain insights into the chronology and genesis of this deposit. The deposit is closely related to granodiorite and diorite porphyry intrusions in space. The orebody occurs in the inner and outer contact zones of the intrusions and is characterized by disseminated, quartz veins, and breccia type mineralization. The main Au-bearing minerals are pyrite, arsenopyrite, and stibnite. The zircon U-Pb ages of the granodiorite and diorite porphyry are 214.8 +/- 1.1 Ma and 211.0 +/- 3.7 Ma, respectively. The Re-Os isochron age of Au-bearing arsenopyrite is 209 +/- 12 Ma. The epsilon Hf(t) values of zircons from the granodiorite range from 4.78 to 9.16, the epsilon Hf(t) of zircons from the diorite porphyry range from -1.81 to 7.05, and the initial Os-187/Os-188 value of Au-bearing arsenopyrite is 0.7851 +/- 0.0079, indicating that the magmas of deposit were derived from the lower crust and ore-forming materials were mainly derived from ancient lower crust. These results show that the Qukulekedong Au-Sb deposit was formed in a Late Triassic post-collision extensional background and is an Au-Sb deposit related to the crust-derived magmatic activity. There is still significant prospecting potential in the depth of the deposit.

The western Tianshan Gold Belt hosts numerous giant and large gold deposits that have been formed during the late Paleozoic amalgamation of the Tianshan orogen. However, little is known about their exhumation histories during the Mesozoic to Cenozoic intracontinental evolution of the orogen. The Carboniferous Katebasu orogenic gold deposit in northwestern China is a new gold discovery within the western Tianshan Gold Belt, and it shares many similarities with other orogenic gold deposits in the belt. In this contribution, new 40 Ar/ 39 Ar and (U–Th)/He ages were combined with previous geochronology and numerical modelling to quantify its post-Carboniferous cooling and exhumation history. The results revealed a three-phase cooling history and two phases of post-mineralization exhumation. We suggest that a large volume ( c. 0.8 km) of the mineralized roof parts of the Katebasu deposit might have been removed during uplift and erosion, whereas significant ore reserves could still exist at depth. The large erosion depth of the Katebasu gold deposit in the Nalati Range of the Chinese western Tianshan also signifies that shallow-emplaced porphyry and epithermal systems that formed prior to Permo-Triassic uplift might have been largely eroded.

The Central Asian Orogenic Belt (CAOB) records a critical stage of Phanerozoic continental growth directly related to substantial juvenile additions during accretionary orogenesis. However, the processes and mechanisms of how juvenile continental growth remain controversial. The Central Tianshan Block (CTB) is a crucial part of the Tianshan orogenic belt. It was involved in the subduction—accretion of the western Paleo-Asian Ocean and the final amalgamation of the Tianshan Orogen in the southwestern CAOB. Multiphase late Paleozoic magmatism is recorded in the Katebasu district, forming one of the most critical granitoid stocks that host significant gold mineralization (i.e., Katebasu Au deposit, 89 t Au @ 2.7 g/t) in the CTB. Based on our new U–Pb ages, geochemical and Sr–Nd–Hf isotopic systematics, in combination with previously published datasets from the adjacent regions, we propose that the Katebasu granitoid stock records the regional tectonic switching from compression to extension of the CTB during the Devonian to Early Carboniferous. The compressional tectonic regime produced extensive juvenile granitoid crust. In contrast, subsequent extensional setting was probably related to slab rollback that may have triggered incremental involvement of juvenile mantle components in producing additional continental crust. Such a tectonic model probably plays an important role in the tectonic evolution and crustal growth of the CTB during the late Paleozoic. On a larger scale, such a long-term “rejuvenation” process probably plays a significant role in the generation of widespread juvenile magmatism and continental growth during the formation of the CAOB.