Relationship Between Orogenic Gold Mineralization and Crustal Shearing Along Ailaoshan‐Red River Belt, Southeastern Tibetan Plateau: New Constraint From Paleomagnetism

Abstract

A new perspective on the relationship between orogenic gold mineralization and crustal shearing is presented in this case study on the gold deposits along Ailaoshan‐Red River shear zone (ARSZ), southeastern Tibetan Plateau. The sinistral ductile shearing along the zone occurred from ca. 31 to 17 Ma resulting in a displacement of ~1,000 km. A series of orogenic gold deposits, represented by the Zhenyuan and Chang'an deposits, occur on western margin of the ARSZ. The timing of mineralization and its relationship to shearing continues to be debated despite extensive geological and geochemical studies. Here we try to clarify this issue by using paleomagnetism to constrain the paleolatitude of mineralized rocks. High temperature magnetization components were isolated from the mineralized rocks, and they record modification by ore‐forming fluid. Their magnetization yields a paleolatitude of 19.9° ± 3.6°N for the Zhenyuan deposit and 16.2° ± 2.9°N for the Chang'an deposit. The paleolatitudes from these deposits are similar to those of ca. 20 Ma strata (19.0° ± 3.6°N), deposited after the large‐scale shearing. By contrast, they differ significantly from the paleolatitude obtained from ca. 130 to 40 Ma strata (28.4° ± 1.1°N), which formed long before the onset of large‐scale shearing. These observations imply that the orogenic gold mineralization occurred after the main offset and associated ductile deformation of the ARSZ. Gold mineralization is thought to be related to ore‐forming fluids and metals derived from the subcrust, rather than from fluids released from shearing‐induced metamorphism of regional strata.

Pre-Late Eocene position of the Lüchun-Jinping microblock in western Yangtze Craton: Constraints from Eocene-Oligocene lamprophyres in southeastern Tibet

“…the paleoposition of the Lüchun-Jinping microblock was spatially at same paleolatitude as the Binchuan and in the western part of the Binchuan area during most of its geological history (Xiao et al, 2003). Furthermore, the paleomagnetic data of the lamprophyres and mineralized intrusions from the Beiya ore district in western Yangtze Craton and from the Chang'an gold district in the Lüchun-Jinping microblock also support this inference (Gao et al, 2018a(Gao et al, , 2018b.…”

Geochronology and Geochemistry of the Granite Xenolith within the Lamprophyre at the Zhenyuan Gold Deposit (Yunnan Province, SW China)

“…33 Ma, was obtained and interpreted as the precise age of the Zhenyuan gold deposit (Wang et al, 2001;Deng et al, 2015). Recently, Gao et al (2018) suggested the ore-forming age of the Zhenyuan gold deposit is ca. 20 Ma by constraining the paleolatitude of mineralized rocks.…”

Interaction Between Mineralization and Rock Magnetization: New Constraints From a Silurian‐Lower Devonian Volcanogenic Massive Sulfide (VMS) Deposit

“…Therefore, it is essential to understand different remagnetization mechanisms and to explore new research objects to conduct paleomagnetic studies in areas lacking suitable strata (Butler, 1992; Kent et al., 1987; X. Zhao & Coe, 1984). The ore deposits have proven to be a promising paleomagnetic research object due to the acquisition of remanence during mineralization (Gao et al., 2018, 2019; Symons et al., 1998). These studies have improved our understanding of the interaction between hydrothermal fluids and rocks, as well as how it affects rock magnetization.…”

“…Zhao & Coe, 1984). The ore deposits have proven to be a promising paleomagnetic research object due to the acquisition of remanence during mineralization (Gao et al, 2018(Gao et al, , 2019Symons et al, 1998). These studies have improved our understanding of the interaction between hydrothermal fluids and rocks, as well as how it affects rock magnetization.…”