Geology and metallogenesis of the Tiegelongnan Cu–Au–Ag deposit, Duolong ore district, Tibet

Abstract

The Tiegelongnan deposit is a giant deposit (>10 million tons Cu resources with an average grade of 0.53%) located in the west of the Bangong Co‐Nujiang metallogenic Belt, where typical porphyry and epithermal types of alteration and mineralization are developed. A compilation of geological features and mineralogical studies revealed that the Tiegelongnan deposit developed two stages of hydrothermal alteration. The early stage was related to porphyry emplacement, developing potassic, phyllic and propylitic alterations, telescoped by the late advanced argillic alteration in the shallow levels. Correspondingly, two stages of mineralization occurred, the early porphyry‐type mineralization being overlapped by the late high‐sulfidation epithermal mineralization. Due to differences in pH, log fO2, K+ activity and temperature of ore‐forming fluids, distinct sulfide minerals of low to extremely high sulfidation states, such as chalcopyrite, tennantite, enargite and covellite, precipitated throughout the entire hydrothermal process. The Tiegelongnan deposit is a complex porphyry metallogenetic system of ‘multiple structures’. The Early Cretaceous andesitic volcanic rocks of the Meiriqiecuo Formation exposed on the surface act as a cap for the ore body, beneath which an oxidizing‐leaching zone lies. Under the cap and the oxidizing‐leaching zone, a porphyry ore body is remoulded by high‐grade high‐sulfidation epithermal hydrothermal mineralization, which gradually transitions to continuous porphyry‐type mineralization at depth.

Petrogenesis of Early Cretaceous volcanic rocks from the Rena-Co area in the southern Qiangtang Terrane, central Tibet: evidence from zircon U-Pb geochronology, petrochemistry and Sr-Nd-Pb–Hf isotope characteristics

“…These adakite-like dacites formed from magmas generated by melting of juvenile lower crustal material and have compositions consistent with adakites that formed in a continental marginal arc. Together with previous data on the Early Cretaceous intrusive and volcanic rocks (especially the Duolong Meriqiecuo volcanic rocks) distributed in the southern QT (She et al 2009;Xin et al 2009;Liu et al 2012;Chen et al 2013;Li et al 2013aLi et al , 2016Wang et al 2015;Sun, 2015;Zhu et al 2016;Wei et al 2017Wei et al , 2018Shi et al 2019), we confidently propose that the sources of the RCA adakite-like magmas were most likely associated with crustal thickening, given that crustal thickening is a common geological phenomenon in arc settings. All of this evidence indicates that the timing of the final closure of the BNO might have been later than the Early Cretaceous (109.5.9-109.6 Ma).…”

“…Xu et al 1985;Dewey et al 1988;Yin et al 1988;Kapp et al 2003Kapp et al , 2005Kapp et al , 2007Raterman et al 2014), as also exemplified by the abundant Early Cretaceous magmatic rocks in the southern QT, which are interpreted as having formed in a continental arc setting (e.g. Kapp et al 2005Kapp et al , 2007Chang et al 2011;Liu et al 2012;Hao et al 2016a, b;Wang et al 2015;Sun, 2015;Li et al 2013aLi et al , b, 2015Li et al , 2016Wei et al 2017Wei et al , 2018Shi et al 2019;this study). Stratigraphic analysis suggests that the QT underwent N-S-directed compression and significant crustal shortening during the Early Cretaceous (Murphy et al 1997;Kapp et al 2005Kapp et al , 2007, probably as a result of the collision of an oceanic plateau with the Qiangtang continental margin (Zeng et al 2021).…”

“…Analytical data of 33 other Duolong volcanic rocks samples collected from (Wang et al . 2015; Sun, 2015; Li et al . 2016; Wei et al .…”

“…109.5-109.6 Ma), similar to the Duolong MF volcanic rocks (105.7-118.5 Ma; Wang et al . 2015; Sun, 2015; Li et al . 2016; Wei et al .…”

“…In addition, they generally show strong enrichments in large ion lithophile elements (LILEs: K, Rb, U and Pb) relative to high-field-strength elements (HFSEs: Nb, Ta, and Ti) in primitive-mantle-normalized multielement (Middlemost, 1994) for classification, (b) K 2 O (wt.%) vs. SiO 2 (wt.%) diagram (Peccerillo & Taylor, 1976), (c) A/NK vs. A/CNK diagram (Maniar & Piccoli, 1989). Analytical data of 33 other Duolong volcanic rocks samples collected from (Wang et al 2015;Sun, 2015;Li et al 2016;Wei et al 2017;Shi et al 2019) are shown for debate. See text for details.…”