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
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本文为国家重点研发计划(编号2019YFA0708604)、国家自然科学基金项目(编号41830216)和IGCP- 662 联合资助的成果。


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

    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 km2)。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以富硅、富碱、弱过铝质花岗岩为特征,主体显示高分异I型花岗岩特点,分异晚期显示出A型花岗岩地化特点。岩浆演化受结晶分异作用和局部上地壳同化混染共同控制。本文依据前人发表的423件样品的地球化学数据,开展有关地球化学和指标的填图,将岩基划分为低硅相、过渡相和高硅相三个区域,分别分布于岩基东西部边缘、中部及南部。其演化程度由东西边缘向南,特别是向南部矿化程度高的部位有增高的趋势。地球化学填图显示,大离子亲石元素Rb、稀土元素Y、高场强元素Nb、Th、U和挥发性元素F的富集也显示类似的空间变化规律,整体具有沿多佛- 赫米蒂奇湾巨型断层带(缝合带)走向近南北向演化的趋势,可能显示了缝合带不同的基底组成,或岩浆具向南的演化趋势。岩基中钨- 锡- 钼矿化与岩浆分异演化程度、流体含量及挥发分组分密切相关, Rb/Sr比值>20的区域与钨- 锡- 钼矿化位置一致。据此推测, Rb/Sr比值>20的Rencontre Lake单元南部、Sage Pond单元及Hungry Grove单元部分区域可能具有良好的成矿潜力。本文提供的研究实例表明地球化学填图可以系统地揭示一个岩基地球化学的变化特征及其对成矿的制约规律。

    Abstract:

    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.

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王朝阳,王涛,林寿发,Cees van Staal.2022.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[J].地质学报,96(2):517-532.
Wang Chaoyang, Wang Tao, Lin Shoufa, Cees van Staal.2022. Geochemical mapping of the Late- Devonian Ackley batholith in the Appalachian orogenic belt (Newfoundland) and its control on mineralization of critical metals[J]. Acta Geologica Sinica,96(2):517-532.

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  • 收稿日期:2021-08-20
  • 最后修改日期:2021-11-09
  • 录用日期:2021-11-09
  • 在线发布日期: 2021-12-09
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