Tectonic Control, Reconstruction and Preservation of the Tiegelongnan Porphyry and Epithermal Overprinting Cu (Au) Deposit, Central Tibet, China

Abstract

The newly discovered Tiegelongnan Cu (Au) deposit is a giant porphyry deposit overprinted by a high-sulfidation epithermal deposit in the western part of the Bangong–Nujiang metallogenic belt, Duolong district, central Tibet. It is mainly controlled by the tectonic movement of the Bangong–Nujiang Oceanic Plate (post-subduction extension). After the closure of the Bangong–Nujiang Ocean, porphyry intrusions emplaced at around 121 Ma in the Tiegelongnan area, which might be the result of continental crust thickening and the collision of Qiangtang and Lhasa terranes, based on the crustal radiogenic isotopic signature. Epithermal overprinting on porphyry alteration and mineralization is characterized by veins and fracture filling, and replacement textures between two episodes of alteration and sulfide minerals. Alunite and kaolinite replaced sericite, accompanied with covellite, digenite, enargite, and tennantite replacing chalcopyrite and bornite. This may result from extension after the Qiangtang–Lhasa collision from 116 to 112 Ma, according to the reopened quartz veins filled with later epithermal alteration minerals and sulfides. The Tiegelongnan deposit was preserved by the volcanism at ~110 Ma with volcanic rocks covering on the top before the orebody being fully weathered and eroded. The Tiegelongnan deposit was then probably partly dislocated to further west and deeper level by later structures. The widespread post-mineral volcanic rocks may conceal and preserve some unexposed deposits in this area. Thus, there is a great potential to explore porphyry and epithermal deposit in the Duolong district, and also in the entire Bangong–Nujiang metallogenic belt.

Application of a Maximum Entropy Model for Mineral Prospectivity Maps

“…• 00 E), with an area of approximately 12,290 km 2 , and is an important copper metallogenic area in China [45][46][47][48]. The magmatic intrusion in the study area is intense, and the overall spatial distribution is east-west.…”

Sulphide geochemistry of the superlarge Tiegelongnan Cu (Au) deposit in Tibet, China: Implication for the mineralization process

“…The BNO commenced subduction towards the north in the Middle to Late Jurassic, possibly within 175–145 Ma (Kapp et al, 2003; Liu et al, 2014; Xu et al, 2017). While the closure time of the BNO is controversial, some studies suggest that the BNO may have closed during the Late Jurassic–Early Cretaceous through arc–arc ‘soft’ collision, most likely within 140–130 Ma (Zhu et al, 2016), and then entered the post‐collisional stage of the orogeny at approximately 110 Ma (Qu, Wang, Xin, Jiang, & Chen, 2012; Song et al, 2018). However, some studies have recommended that the BNO was still subducting northward during the Early Cretaceous, possibly within 106–125 Ma (Geng et al, 2016; Li et al, 2014; Sun et al, 2017; Xu et al, 2017).…”

“…The main ore body presents as a thick slab‐like form, of which the width, length, and depth are approximately 1,400, 1,800, and 960 m, respectively. The total reserves are >11 million tons of copper and ~120 tons of gold, with average grades of 0.53% and 0.12 g/t, respectively (He et al, 2018; Song et al, 2018). Mineralization mainly occurs in the Sewa Formation and the granodiorite porphyry zone (Figure 1a).…”

Geology of the Josemaría Porphyry Copper-Gold Deposit, Argentina: Formation, Exhumation, and Burial in Two Million Years

“…This is exemplified by the Cretaceous deposits at Pebble, Alaska, and Tiegelongnan, Tibet, which were exhumed sometime during the ~25-and 8-m.y. intervals, respectively, that preceded their concealment beneath postmineral cover (Lang et al, 2013;Song et al, 2018). Nonetheless, extremely rapid unroofing was documented at the Late Devonian Hugo Dummett porphyry copper-gold deposit in the Oyu Tolgoi district, Mongolia, where as little as 1 m.y.…”