Xudong Che

Geochronological Framework of the Penggongmiao Granite Batholith

representative of the large granite batholiths in the middle Nanling region. It is located in the south-eastern Hunan Province, about 90 km south of the Chenzhou city. Geographically it stretches across four counties, i.e. Zixing, Guidong, Yanling and Yongxing, presenting a palmate shape from NE to SW in whole, with a total exposure area of over 970 km (see fig. 1). In recent years, several tungsten deposits and mineralization points have been found in succession at its southern boundary, such as the Zhangjialong, Zhenkou and Yangmeikeng, etc. mines. A conclusion was already made previously on the Caledonian emplacement age for the Penggongmiao granite batholith (Nanjing University, 1961; Li Pu et al, 1964; Guiyang Institute of Geochemistry, 1979; Hunan Bureau of Geology and Mineral Resources, 1995; Bo Daoyuan, 2006). However, many scientific problems have not been resolved, such as the subdivision of intrusive phases, the degree of differentiation and evolution, the distribution of individual intrusive phases, the relationship with tungsten mineralization, and the parental source materials for the tungsten ores. These problems have been arising significant interests of many geologists. This paper focuses on the isotopic age dating results of the zircon UPb method for different granite intrusive phases and the mica Ar-Ar method for the related pegmatites. The results are shown in the Table 1. On this basis, we attempt to establish a geochronological framework for the Penggongmiao granite batholith. Our study shows that during the Caledonian period, the Pengongmiao granite batholith can be subdivided into four intrusion phases: the early stage granite (G1), the main stage granite (G2), followed by the first additional stage of granite dikes (G3), and the second additional stage of Tangshi pegmatite. The magmatic activity also extended to the Hercynian period to form the tourmarine-rich finegrained muscovite granite (G4) and pegmatite.. The dating results of the Caledonian period: The early atage granite (G1) spreads over the western part of the batholith and occupies about 25% of the entire area of this rock body. Petrologically, it is fine-grained biotitic granite, with a minor amount of hornblende. Due to strong weathering resistance feature, granite of this stage morphologically expresses as the mountain ridge in the western part of this pluton. This stage is supported by the zircon U-Pb dating results of three samples with ages from 447.3 Ma to 442.2 Ma. The major stage granite (G2) accounts for over 70% of the rock body in area and Petrologically is coarseZHANG Wenlan, CHE Xudong, WANG Rucheng, ZHANG Rongqing and YANG Zhen, 2014. Geochronological Framework of the Penggongmiao Granite Batholith. Acta Geologica Sinica (English Edition), 88(supp. 2): 1041-1042.

A New Potential Caledonian-Indosinian Ore Concentration Area: Evidence from Diagenesis and Mineralization Ages of the Miao'ershan-Yuechengling Region

The Miao’ershan–Yuechengling composite granite, located in northern Guangxi at the western section of the Nanling Range, is a multi-period and multi-stage composite pluton with an exposed area of more than 3000 km (Fig. 1). Paleozoic and Proterozoic strata are exposed around it, and magmatic activities mainly occurred during the Caledonian and Indosinian periods. Till now, more than one hundred W-Sn-Mo-Pb-Zn-Cu (U) deposits and ore occurrences have been discovered along the inner and outer contact zones of this granite. Through recent years’ research, we infer that this area is not only a preferred area for studying granite and mineralization in Caledonian and Indosinian periods, but also a potential CaledonianIndosinian ore-concentrated area.

A new style of rare metal granite with Nb-rich mica: The Early Cretaceous Huangshan rare-metal granite suite, northeast Jiangxi Province, southeast China

Abstract In rare-metal granites, niobium and tantalum are generally hosted by Nb–Ta oxides. However, in SE China, the Nb-specialized Huangshan granites are a unique occurrence in which Nb is essentially hosted by Li–Fe micas. The Huangshan granites are part of the Early Cretaceous (Late Yanshanian) Lingshan granite complex and belong to the A-type granite series, with two facies differing by their mica compositions: medium-grained “protolithionite” granite and medium-grained lithian (lithium-rich) annite granite. The granites are characterized by elevated whole-rock Nb contents (average 144 ppm in “protolithionite” granite and 158 ppm in annite granite), quite low Ta contents (average 9 and 4 ppm, respectively), leading to very high Nb/Ta ratios (average 15.3 and 31.2). Niobium is mainly hosted in the micas, with an average Nb content of 1347 ppm in the lithian annite and 884 ppm in the “protolithionite,” which is the highest ever reported in granitic mica. With an estimated endowment of ~80 kt Nb, the Huangshan granites represent a new style of potential Nb resource. Contrasting with the great rarity of columbite, there is abundant Hf-rich zircon, Y-rich fluorite, and Th-rich fluocerite included in the Huangshan micas. Such accessory minerals being typical of alkaline rhyolitic magmas and niobium enrichment in the Huangshan granites results from A-type melt. The extreme Nb enrichment in the micas results from the highly compatible behavior of Nb in this melt, combined with the high magma temperature (estimated at 790–800 °C) and possibly enhanced magma oxidation.