Exhumation of the Mesozoic Guojialing Granodiorite: Implication for the Preservation of Gold Deposits in the Jiaobei Terrane, China

摘要

Preservation conditions are very important for mineral systems and a suitable exhumation process is critical for endogenetic deposits, especially for those deposits formed in orogenic settings, where deposits are inclined to erode away due to strong uplift. The Guojialing batholith, intruding into the Linglong granites and the Jiaodong Group right before regional gold mineralization, is one of the most important gold ore-hosting Mesozoic intrusions in the Jiaobei terrane. Gold deposits and the intrusion together underwent similar tectonothermal evolutionary processes. Exhumation and denudation process of the Guojialing granodiorite was constrained by biotite geobarometry and apatite fission track (FT) analysis. Biotite geobarometric data yields an emplacement depth of 3.0 km, while denudation since 110 Ma was calculated from the FT data at about 2.7 km. FT inverse modeling revealed a rapid uplift since ca 100 Ma. Compared with the gold ore-forming depth which is confined between 2.5 and 9.5 km by fluid inclusion studies, great gold potential in the depths is inferred in the Jiaobei terrane. Our result is consistent, to some extent, with the hypothesis of a Mesozoic paleoplateau in East China.