Low-temperature thermochronology of the Longmala - Mengya’a Pb-Zn deposits (southern Tibet): Implications for ore exhumation and preservation

• Published in: Ore geology reviews Vol. 160; p. 105611
• Main Authors: He, Zhiyuan, Zhong, Linglin, Su, Wenbo, Zhong, Kanghui, Glorie, Stijn, Ren, Fei, Shen, Xiaoming, Song, Shida, Dou, Jie, Qin, Qin, De Grave, Johan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2023
• Subjects: Exhumation and preservation; Gangdese metallogenic belt; Longmala and Mengya’a Pb-Zn deposits; Low-temperature thermochronology; Southern Tibet; Low-temperature thermochronology; Gangdese metallogenic belt; Exhumation and preservation; Southern Tibet; Longmala and Mengya’a Pb-Zn deposits
• ISSN: 0169-1368; 1872-7360
• DOI: 10.1016/j.oregeorev.2023.105611

[Display omitted] •The Miocene moderate cooling exposed the Longmala and Mengya’a ore bodies near the surface.•Basement exhumation was prompted by both tectonic and climatic factors in the central and southern Lhasa sub-terranes.•Areas that display late Cenozoic accelerated cooling in the Gangdese belt are potential targets for ore exploration. The large Gangdese metallogenic belt, located in the southern part of the Tibetan Plateau, hosts a variety of magmatic-hydrothermal ore deposits. Previous works in the area primarily concerned the ore genesis, while the exhumation history of these ore deposit has received less attention. In this contribution we explore the multi-stage thermo-tectonic evolution of the Longmala and Mengya’a Pb-Zn deposits, two large magmatic-hydrothermal ore deposits in the central Lhasa sub-terrane. In more detail, the thermal history of granitoids and deformed Paleozoic sediments inside and on the periphery of the ore districts have been constrained by low-temperature thermochronological methods, including the zircon (U-Th)/He and apatite fission track thermochronology. Additionally, zircon U-Pb geochronology was conducted on granitic host rocks to determine their emplacement ages. Our thermochronological data and inverse thermal history modeling results reflect two phases of accelerated basement cooling during the Cenozoic (i.e., ∼46–41 Ma and  ∼20–5 Ma), interpreted as exhumation phases. The ore body was exhumed to the near surface during the Miocene, which provides essential information for ore exploration in the region. We also explore the degrees of basement rock exhumation along the Gangdese metallogenic belt and their spatio-temporal relations to major ore deposit distributions. It is suggested that complex interactions between tectonic-structural activities and surface erosion occurred during the late Oligocene-Miocene (∼25–5 Ma), which resulting in widespread exhumation along the Gangdese batholith. During this period, the ore-bearing rocks were gradually (with medium to high cooling rates) exhumed to the near-surface from ∼3–4 km crustal depth, making these ore deposits feasible for commercial mining.