The Temagami geophysical anomaly (Ontario, Canada): geological cause and relationship to the 1.85 Ga Sudbury impact event

Temagami 地球物理异常（加拿大安大略省）：地质原因及其与 1.85 Ga 萨德伯里撞击事件的关系

• 批准号: 418960271
• 负责人: Professor Dr. Hartwig E. Frimmel
• 金额: --
• 依托单位: Lehrstuhl für Geodynamik und Geomaterialforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418960271?language=en
• 关键词: Temagami; geophysical; anomaly; Ontario; Canada

This project attempts to explain the ultimate geological cause of one of the largest, hitherto unexplained, magnetic anomalies in North America, the Temagami geophysical anomaly in Ontario, Canada. The anomaly is of outstanding scientific and economic interest because it is directly adjacent to the 1.85 Ga Sudbury Complex - the second largest impact structure on Earth and one of the world’s richest mining districts thanks to widespread Ni-Cu-PGE-sulfide mineralization. The Temagami Anomaly mirrors the magnetic anomaly caused by the Sudbury Complex in terms of shape, size and intensity. Lack of outcrops and, until recently, of bore holes, prevented a proper geological understanding, and whatever genetic link with the Sudbury Complex has remained pure speculation. Preliminary petrological studies by the applicant and the anticipated project scientist (PhD student) on the first deep drill hole sunk into the centre of the Temagami Anomaly revealed the presence of dioritic rocks at 2 km depth, which bear similarities with offset dykes in and around the Sudbury Complex. This raises the possibility of a genetic link with the Sudbury impact event, which if proved correct, would open up an entirely new perspective on our understanding of the Sudbury Complex and its exploration potential. Thus, the principal aim of this project is to test for such a genetic link and to provide a geological explanation for the geophysical anomaly by comparing new data on the petrology, alteration history, geochemistry, isotopic composition and geochronology to be acquired from drill core and surface samples from the area of the Temagami Anomaly with available data on the Sudbury Complex and potentially equivalent rocks in the wider region. This will include layered mafic and ultramafic intrusions, mafic dyke swarms, carbonatite stocks, and sedimentary iron formations, all of which occur in the area, bear significant economic potential, and could be possible candidates for the observed magnetic anomaly. Our preliminary observations revealed also widespread hydrothermal alteration and brecciation, whose origin and bearing on the magnetic anomaly is unclear. Thus, a further goal of the project will be to characterize this alteration and to establish its significance in terms of the cause of the Temagami Anomaly, the genesis of the Sudbury structure and the metallogeny of the area.

该项目试图解释北美最大的、迄今尚未解释的磁性异常之一--加拿大安大略省的Temagami地球物理异常--的最终地质原因。这一异常具有突出的科学和经济价值，因为它直接毗邻1.85Ga萨德伯里综合体--这是地球上第二大撞击结构，也是世界上最丰富的矿区之一，这要归功于广泛的镍-铜-铂族硫化物矿化。Temagami异常在形状、大小和强度上反映了萨德伯里杂岩造成的磁异常。直到最近，露头和钻孔的缺乏阻碍了人们对地质的正确理解，无论与萨德伯里杂岩有何遗传联系，都只是纯粹的猜测。申请者和预期的项目科学家(博士生)对Temagami异常中心的第一个深钻孔进行的初步岩石学研究显示，在2公里深的闪长岩中存在闪长岩，这些岩石与萨德伯里建筑群及其周围的偏置岩墙相似。这增加了与萨德伯里撞击事件存在遗传联系的可能性，如果这被证明是正确的，将为我们对萨德伯里综合体及其勘探潜力的理解打开一个全新的视角。因此，该项目的主要目的是测试这种成因联系，并通过将从Temagami异常区域的钻芯和地表样品中获得的岩石学、蚀变历史、地球化学、同位素组成和地质年代学的新数据与更广泛区域的萨德伯里杂岩和可能相当的岩石的现有数据进行比较，为地球物理异常提供地质解释。这将包括层状镁铁质和超镁铁质侵入体、镁铁质岩墙群、碳酸盐岩岩群和沉积铁建造，所有这些都出现在该地区，具有巨大的经济潜力，并可能成为观测到的磁异常的候选者。我们的初步观测还发现了广泛的热液蚀变和角砾化作用，其成因和与磁异常的关系尚不清楚。因此，该项目的另一个目标将是确定这一蚀变的特征，并确定其在Temagami异常的原因、萨德伯里构造的成因和该地区的成矿作用方面的意义。