Geochronology and Geochemistry of Ore-Hosting Rhyolitic Tuff in the Kengdenongshe Polymetallic Deposit in the Eastern Segment of the East Kunlun Orogen

Abstract

The Kengdenongshe Au–Ag–Pb–Zn polymetallic deposit, a newly discovered large-scale polymetallic deposit in the southeastern section of the East Kunlun Orogen (EKO), contains an Au resource of 40 t, Ag resource of 690 t and Pb–Zn resource of 10.5 × 105 t. The ore-bearing rocks are mainly composed of laminar barite and rhyolitic tuff. In this study, LA-ICP-MS zircon U–Pb dating and whole rock major and trace elements analyses have been conducted on the ore-bearing rhyolitic tuff. LA-ICP-MS zircon U–Pb dating data show that these rhyolitic tuffs were emplaced at ca. 243.3 ± 1.6 Ma. The samples show similar features to those of S-type granites, including high contents of SiO2 (76.4–82.6 wt. %) and Al2O3 (11.0–12.7 wt. %) and relatively low concentrations of Na2O (0.35–2.43 wt. %) and CaO (0.095–0.124 wt. %), with high A/CNK (molar [Al2O3/(CaO + Na2O + K2O)]) (1.72–2.03) and K2O/Na2O ratios (1.41–17.1). Further, they exhibit depletion in HFSEs (High Field Strength Elements) and enrichment in LREEs (Light Rare Earth Element) with negative Eu anomalies (Eu/Eu* = 0.51–0.64). These geochemical characteristics indicate that the Kengdenongcuo rhyolitic tuff originated from the fluid-absent melting of a plagioclase-poor, clay-rich metapelitic source and experienced minor fractional crystallization. In combination with arc-type magmatism and contemporaneous syn-collision granitoids in the region, the Kengdenongcuo tuff formed in a continental collision setting, implying that the Bayan Har–Songpan Ganzi Terrane collided with the East Kunlun Terrane and the Paleo-Tethys Ocean was closed at the period of ~243 Ma. The Kengdenongcuo polymetallic deposit formed at about the same time.

Geochronology and geochemistry of the Yidi'nan quartz diorite in the West Qinling, China: Implications for evolution of the Palaeo‐Tethys Ocean

“…However, quartz diorite lack typical peraluminous minerals (e.g., cordierite, andalusite and garnet) or alkaline mafic minerals (e.g., aegirine, riebeckite) but have a magmatic assemblage of amphibole and biotite (Figure 3b,c), indicating that the quartz diorite belongs to the I‐type magmatism. Trace elements such as Rb, Y, and Th are also used as distinguishing characteristics of I‐ and S‐type granites (Li et al, 2007; Liang et al, 2019). The characteristics also show that Yidi'nan granitoid belongs to I‐type granites.…”

Petrogenesis, Sources, and Tectonic Settings of Triassic Volcanic Rocks in the Ela Mountain Area of the East Kunlun Orogen: Insights from Geochronology, Geochemistry and Hf Isotopic Compositions

“…The igneous rocks of the P3 stage represent the products of post-collisional magmatism [11,47]. The intrusive and volcanic rocks of the P2 stage are widespread in the East Kunlun Orogen, but there is a great controversy about their formation environment, including post-collision [12,13], syn-collision [14][15][16], and subduction [17][18][19]. The volcanic rocks studied in this paper are in the range of the P2 stage; in the rock association of this stage, the intrusive rocks are mainly granodiorite [14,17,44], monzogranite, syenogranite [45,47], and a small amount of mafic-intermediate rocks [14,44,45].…”

“…During the Late Triassic, the mafic dikes with intraplate basalt characteristics [8,9] and extension-related A-type granites [10,11] appeared simultaneously, reflecting the extensional tectonic setting of post-collision. These previous achievements basically clarify the respective dynamic evolution background of the Early Triassic and Late Triassic in the East Kunlun Orogen, but there is great controversy about the formation environment of igneous rocks in the Middle Triassic-early Late Triassic in the East Kunlun Orogen, including post-collision [12,13], syn-collision [14][15][16], and subduction [17][18][19]. In addition, the Ela Mountain area is located at the easternmost point of the East Kunlun Orogen, which is the junction between the East Kunlun Orogen and the West Qinling Orogen.…”

Types and Quantitative Characterization of Microfractures in the Continental Shale of the Da’anzhai Member of the Ziliujing Formation in Northeast Sichuan, China

“…The belt overlaps with the arcshaped skirt belt in eastern Sichuan. During the Jurassic period, due to the disappearance of the Songpan Ganzi Sea and the Western Sea, all of the surrounding areas were surrounded and evolved into inland lakes [51][52][53]. The Early to Middle Jurassic basins were deep lakes, semi-deep lakes, and shallow lakes, where rivers, lakes, and deltas formed [54,55].…”