Geochronological and geochemical constraints on the origin of Yaguila Cretaceous and Palaeogene ore-bearing quartz porphyries, Central Lhasa Terrane, Tibet

Abstract

The quartz porphyries at Yaguila, Tibet, host important polymetallic ore deposits, but their age, source and evolution have received insufficient attention. In this study, LA-ICP-MS U-Pb zircon ages revealed that these quartz porphyries were formed in two stages, i.e. precollisional Early Cretaceous period (ca. 128 Ma) and late subduction to initial collision Palaeogene period (ca. 65 Ma). Geochemical evidence including whole-rock major element, trace element and rare earth element, zircon Hf isotopes together with sulphide Pb isotopes suggests the Early Cretaceous quartz porphyries could have formed by means of partial melting of crustal materials from Lhasa Terrane basement in a thickened crustal tectonic setting, whereas the Palaeogene quartz porphyries by enhanced input of mantle components probably were associated with slab rollback and breakoff at that time. Granitoid magmas produced in this way ascended to upper crustal level and interacted with marbles and breccias to form Pb-Zn-Ag ore bodies and Mo ore bodies, respectively. Age and geochemical constraints on the Early Cretaceous and Palaeogene polymetallic ore bodies not only have favoured a skarn and hydrothermal vein origin over a submarine exhalative sedimentary origin but also have consummated ore deposits metallogenic series and built up a reconnaissance model along the Lhasa Terrane.

Zircon U–Pb dating, geochemistry, and Sr–Nd–Pb–Hf isotopes of the subvolcanic intrusion from Beina Pb–Zn–(Ag) deposit in the southern Lhasa terrane, Tibet: Implications for petrogenesis and mineralization

“…In addition, the samples have extremely radiogenic Sr ( 87 Sr/ 86 Sr (i) = 0.7084 to 0.7092; Figure ) and Pb isotopes ( 206 Pb/ 204 Pb = 18.61–18.74, 207 Pb/ 204 Pb = 15.65–15.68, 208 Pb/ 204 Pb = 38.99–39.14; Figure ) but non‐radioactive Nd isotopes (ε Nd(t) = −8.6 to −7.2; Figure ) and Hf isotopes (ε Hf(t) = −8.6 to −4.7; Figure ), revealing that the ancient crustal material dominated the source. These characteristics are consistent with the S‐type intrusions such as Chagele granite porphyry (Wang, Zhou, et al, ), Longgen granite porphyry (Duan et al, ), Narusongduo granite porphyry (Fu et al, ; Ji, ), and Yaguila quartz granite (Fu et al, ; Gao et al, ) in the central Lhasa terrane. However, the mineralization‐related Longmala biotite monzogranite (Wang et al, ) and Leqingla granodioritic porphyry (Ma et al, ; Zhou et al, ) were considered as I‐type granites.…”

“…The Proterozoic–Precambrian metamorphic basement of the central Lhasa terrane after Pan et al () and Zhang et al (); Yarlung Zangbo ophiolite and Himalayan basement after Liu et al (). Data for the Longgen granite porphyry are from Zhang et al (unpublished data); data for the Narusongduo granite porphyry are from Yang et al (); data for the Yaguila granite porphyry are from Gao, Lan, Chen, and Tang (). Symbols are the same as in Figure [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…The Pb–Zn mineralization in the central Lhasa terrane is mainly associated with felsic intrusions (Duan et al, ; Fu et al, ; Gao et al, ; Hou et al, ; Jiang et al, ; Wang, Zhou, et al, ; Zheng, Sun, et al, ; Zhou et al, ). However, the genetic types of the felsic intrusions are still debated, Fu et al () proposed that they are S‐type granites, while Zhou et al () argued that they are I‐type granites (Figure ).…”

“…These ore‐forming intrusions were considered as S‐type granites (Fu et al, ), while Zhou et al () argued that they are I‐type granites. Through study and analysis of the metallogeny of Pb‐Zn ores in the Lhasa terrane, it was found that Pb–Zn–(Ag) mineralization is mainly related to S‐type granites such as Beina rhyolite porphyry, Chagele granite porphyry (Wang, Zhou, et al, ), Longgen granite porphyry (Duan et al, ), Narusongduo granite porphyry (Ji, 2013; Fu et al, ), and Yaguila quartz granite (Fu et al, ; Gao et al, ). While I‐type granites such as Longmala monzonitic granite (Wang et al, ) and Leqingla granodiorite porphyry (Ma et al, ; Zhou et al, ) have a close relationship with Pb–Zn–(Fe–Cu) mineralization.…”

“…The Pb-Zn mineralization in the central Lhasa terrane is mainly associated with felsic intrusions (Duan et al, 2014;Fu et al, 2017;Gao et al, 2017;Hou et al, 2015;Jiang et al, 2018;Wang, Zhou, et al, 2012;Zhou et al, 2017) 33 (Figure 7). These characteristics, together with the presence of CIPW-norm corundum (mostly >1%) in the samples (Table 4) and the observation of inherited cores in the zircon CL images ( Figure 5), indicate that the Beina rhyolite porphyry belongs to S-type Sun and McDonough (1989).…”