阿巴拉契亚造山带(纽芬兰岛)阿克利巨型花岗岩基地球化学填图及其成矿制约

阿巴拉契亚造山带加拿大纽芬兰岛东南部发育一晚泥盆纪阿克利巨型花岗岩基(～2500 km2).该岩基侵位于甘德和阿瓦隆地块的多佛-赫米蒂奇湾巨型断层带之间,内部发育钨-锡-钼矿床及相关的矿化.本文锆石年代学研究显示,岩基中Tolt单元侵位于378±2 Ma,各单元年龄基本一致,为同期岩浆多次侵位的产物.岩基中主要岩石类型...

Geochemical mapping of the Late- Devonian Ackley batholith in the Appalachian orogenic belt (Newfoundland) and its control on mineralization of critical metals

The Late Devonian (378±2 Ma) Ackley giant granitic batholith is located in the Appalachian orogenic belt in southeast Newfoundland, Canada.Thisbatholith was emplaced into the boundary between the Gander and Avalon blocks and hosts W- Sn- Mo mineralization. Geochronological studies show that the various units in the batholith have the same age and the batholith is the product of multi- stage emplacement processes of magma in the same period. The granites are characterized by enrichment in silica and alkali, and weak- peraluminum. The main rock units exhibit features of highly differentiated I- type granites, while the late stage rock units show the geochemical properties of A- type granites. Previous studies suggest that the evolution of magma is affected by fractional crystallization and local assimilation of the upper crust.In this study, we carried out mapping of geochemical elements and indicators in the Ackley batholith based on the published geochemical data of 423 samples. The batholith can be divided into three domains of low- silica facies, transitional facies and high- silica facies, which are distributed along the east and west margins and the central and southern parts of the batholith, respectively. The degree of evolution in the batholith increases from the east and west margins to southern margin of the batholith, where the mineralized occurs. The geochemical mapping shows that the distribution pattern of enrichment in LILE (Rb), REE (Y), HFSEs (Nb, Th, U), and volatile elements (F) are similar and there is an evolution trend from north to south, along the Dover- Hermitage Bay Fault (suture zone). The W- Sn- Mo mineralization is closely related to the degree of magma evolution, fluid content and volatile components. The domain with ratio of Rb/Sr>20 coincides with the location of W- Sn- Mo mineralization. These indicate that the southern part of the Rencontre Lake unit, Sage Pond unit and some areas of the Hungry Grove unit with Rb/Sr ratio>20 have mineralization potential. The geochemical mapping can systematically reveal the geochemical characteristics of the batholith and their constraints on mineralization.