Reconstructing the Geochemical Signature of Sudbury Breccia, Ontario, Canada: Implications for Its Formation and Trace Metal Content
Reconstructing the Geochemical Signature of Sudbury Breccia, Ontario, Canada: Implications for Its Formation and Trace Metal Content
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重建加拿大安大略省萨德伯里角砾岩的地球化学特征：对其形成和微量金属含量的影响
DOI：
10.2113/econgeo.111.7.1705
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发表时间：
2016
期刊：
影响因子：
5.8
通讯作者：
J. Weirich
中科院分区：
文献类型：
--
作者：
J. O’Callaghan;G. Osinski;P. Lightfoot;R. Linnen;J. Weirich
萨德伯里角砾岩是加拿大安大略1.85 Ga萨德伯里火成杂岩下盘的假玄武玻璃质角砾岩。角砾岩通常发育在围岩类型不同的区域，是下盘式铜镍铂族元素硫化物矿化的共同宿主，在萨德伯里火成杂岩基底的大型接触型富镍铜矿床的直接下盘中发育。萨德伯里角砾岩的成因有三种模式：（1）目标岩石的原地摩擦或冲击熔融，（2）目标岩石的碎裂，和/或（3）来自萨德伯里火成杂岩的外来撞击熔体注入角砾状火山口底部。这项研究报告了来自萨德伯里结构周围六个不同位置的萨德伯里角砾岩和矿化近端和远端相关容矿岩样本的新矿物学和地球化学数据。混合模型被用来构建萨德伯里角砾岩矩阵的组成，使用的组合围岩和石英diaphragm从偏移岩脉，这被认为是提供了一个估计的组合物的早期熔融片。我们证明，角砾岩基质可以成功地从下盘岩性建模，没有要求的影响熔体片的贡献。相反，我们提出了一个动态的，准原地熔融模型，其中的角砾岩的矩阵是由高温熔融的下盘岩性的一部分。这些夹杂物和晶体负载熔体混合和运输到拉伸断裂带，开发邻近的弱点在围岩。萨德伯里角砾岩的主成分分析表明，微量金属含量的角砾岩，远离矿化与下盘的镁铁质单位同化。相比之下，基质的萨德伯里角砾岩开发更接近矿带的贡献来自分馏硫化物熔体和/或贡献的热液再活化金属的金属。因此，通过比较萨德伯里角砾岩的微量金属含量与当地下盘岩性，可以建立基线，可以帮助确定异常金属的贡献，可能来自下盘矿物系统的周边。
The Sudbury breccia is an impact-generated pseudotachylitic breccia formed in the footwall of the 1.85 Ga Sudbury Igneous Complex in Ontario, Canada. The breccia is commonly developed in areas of contrasting country-rock types, and it represents a common host to footwall-style Cu-Ni-platinum group element sulfide mineralization, developed in the immediate footwall of large, contact-type, Ni-Cu–rich ore deposits at the base of the Sudbury Igneous Complex. Three models have been proposed for the genesis of the Sudbury breccia: (1) in situ frictional or shock melting of target rocks, (2) cataclasis of the target rocks, and/or (3) injection of allochthonous impact melt from the Sudbury Igneous Complex into the brecciated crater floor. This study reports new mineralogical and geochemical data for samples of Sudbury breccia and associated host rocks, both proximal and distal to mineralization, from six different locations around the Sudbury structure. A mixing model was used to construct the composition of the Sudbury breccia matrix, using a combination of country rock and quartz diorite from the offset dikes, which are believed to provide an estimate of the composition of the early melt sheet. We demonstrate that the breccia matrix can be successfully modeled from footwall lithologies with no requirement for a contribution from the impact melt sheet. Instead, we propose a dynamic, parautochthonous in situ melt model, where the matrix of the breccia was derived in part by high-temperature melting of footwall lithologies. These inclusion and crystal-laden melts were mixed and transported into tensile fracture zones that developed adjacent to weaknesses in the country rocks. Principal component analysis of Sudbury breccia indicates that the trace metal content within the breccia that developed distal from mineralization is associated with assimilation of mafic units in the footwall. In contrast, the matrix of Sudbury breccia developed closer to mineral zones has a contribution of metal derived from the fractionated sulfide melt and/or a contribution of hydrothermally remobilized metal. Thus, by comparing the trace metal content in Sudbury breccia with local footwall lithologies, baselines can be established that can help to identify anomalous metal contributions that may be derived from the periphery of a footwall mineral system.
影响因子：
2.7
作者：
Barnett IJ;Lin X
通讯作者：
Lin X
含白云母石英岩中的假速晶石：同震摩擦引起的石英熔化和塑性变形
影响因子：
3.1
作者：
Bestmann;Pennacchioni;Göken;de Wall
通讯作者：
de Wall