Petrogenesis of Early Mesozoic Furong pluton in central Hunan, China and its implications for tungsten mineralization

Abstract

The Furong pluton, located in central Hunan, China, hosts numerous tungsten veins within and around the granite, which are of great economic significance. However, its petrogenesis and related mineralization are poorly constrained. In this study, we used U−Pb dating, petrological and geochemical methods to ascertain the emplacement time, classification of granitic rock, nature of the source rocks, formation mechanism, and its geodynamic implications for the Furong pluton. It is shown that the granite is precisely determined to be formed at ~210 Ma, and belongs to the moderately-fractionated S-type granite. Combined with regional tectonic setting, it is concluded that the pluton was formed due to crust extension and thinning followed by plate collision and compression in South China. It is also revealed that tungsten mineralization and Indosinian granites exhibit a close temporal, spatial and genetic relationships, and further exploration of tungsten deposits within and around the granite in central Hunan, even in South China, is urgently needed.

1. Introduction

Mesozoic granites are widely distributed in South China [1−3], and previous researches have mostly focused on the Late Mesozoic (Yanshanian) granite and its related mineralization during the past several decades [4−7]. In contrast, the Early Mesozoic (Indosinian) granite and its relevant mineralization have been ignored for a long time due to their relatively limited outcrop area [2,8,9]. In recent years, many researchers have proposed that Indosinian magmatism is relatively widespread in South China [10−13]; however, up to now, the affected scope and the intensity of the Indosinian magmatic activity have been seriously under-estimated [14], and its mineralization potential has received less attention.

The Early Mesozoic granite mainly exhibits a planar distribution in Hunan, Jiangxi, Guangdong, Guangxi, and Fujian Provinces in South China [2,14], with a small quantity and scattered distribution [14,15]. Among them, the Xiangzhong area (central Hunan, China) is the most important distribution region, and many tungsten (W) mineralizations related to these granites occur in this area. The important tungsten deposits and their associated granites include the Xingfengshan Au−W deposit and the adjacent Baimashan pluton, the Baojinshan Au−W deposit and the adjacent Ziyunshan pluton, the Darongxi W deposit and the adjacent Dashenshan pluton, the Muguayuan W deposit and the adjacent Sanxianba pluton, and the Situpu W deposit and the adjacent Weishan pluton (Fig. 1 [16]). Although some petrological and geochemical researches have been carried out on these Early Mesozoic granites in central Hunan, China in recent years [8,9,14], it is still unclear whether there are multiple episodes of granitic magma emplacement during the Early Mesozoic, the nature of its magma source is still ambiguous, and the associations between the granites and tungsten mineralization are still disputed.

The Furong pluton, adjacent to the Weishan pluton, was considered to be formed during the Mesozoic, but robust geochronological constraints on its emplacement are still absent. Many tungsten-bearing quartz veins occur within this pluton and some occur along the contact zones, indicating a close spatial relationship with tungsten mineralization. However, the petrogenesis of the Furong pluton and its genetic link to tungsten mineralization remain poorly understood. This study aims to address these issues through integrated U−Pb dating, petrological, and geochemical analyses.