Hydrothermal wall-rock alteration and formation of the gold-bearing quartz-fuchsite vein at the Dome Mine, Timmins area, Ontario, Canada
Hydrothermal wall-rock alteration and formation of the gold-bearing quartz-fuchsite vein at the Dome Mine, Timmins area, Ontario, Canada
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加拿大安大略省蒂明斯地区圆顶矿热液围岩蚀变和含金石英紫铜矿脉的形成
DOI：
10.2113/gsecongeo.86.3.620
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发表时间：
1991
期刊：
影响因子：
5.8
通讯作者：
J. Crocket
中科院分区：
文献类型：
--
作者：
R. Moritz;J. Crocket
Timmins地区Dome矿的近垂直含金石英-Fuchsite矿脉位于与板岩单元接触的高度碳酸化岩石中。矿脉围岩的化学成分（无水基）和元素间诊断关系表明其原岩为科马提岩。超镁铁岩强烈的碳酸盐化作用伴随着K2 O、CaO、Rb、Sr、Ba、Au、As和Sb的增加和H2 O的损失。在围岩中可以识别出两个不同的蚀变阶段：科马提质原岩的初始普遍碳酸盐化，以及后来的以位于碳酸盐化岩石区的石英长石斑岩透镜为中心的更强烈的紫红色黄铁矿蚀变。除了较浅的水平，没有明显的蚀变信封是关于石英-Fuchsite静脉，这实际上是在最少的蚀变科马提岩。这表明成脉流体基本上与当地围岩处于热平衡和成分平衡。石英Fuchsite脉被解释为一个渐进的围岩蚀变序列在区域压缩变形过程中产生的一个组成部分。早期碳酸盐置换反应导致科马提岩渗透率急剧降低。因此，垂直热液流逐渐局限于反应性较低的石英-长石斑岩，并在碳酸化的科马提岩中建立了高孔隙流体压力制度，为板岩-科马提岩接触附近的石英-Fuchsite脉的水力压裂和置换创造了有利条件。这种交代作用和构造作用引起的导管为从深部和邻近围岩中泵送流体提供了有利的排水通道。金的引入与晚紫红色黄铁矿蚀变事件有关。
A subvertical gold-bearing Quartz-Fuchsite vein at the Dome mine, Timmins area, is located in a highly carbonatized rock at the contact with a unit of slate. The chemical composition (anhydrous basis) of the wall rock of the vein and diagnostic interelement relations indicate that its protolith is a komatiite. Intense carbonatization of the ultramafic rock was accompanied by gains in K 2 O, CaO, Rb, Sr, Ba, Au, As, and Sb, and by loss of H 2 O. Two distinct alteration stages can be recognized in the wall rock: an initial pervasive carbonatization of the komatiitic protolith, and a later, more intense fuchsite-pyrite alteration centered on a quartz-feldspar porphyry lens located in the zone of the carbonatized rock. Apart from shallower levels, no distinct alteration envelope is developed about the Quartz-Fuchsite vein, which actually lies in the least altered komatiite. This suggests that the vein-forming fluid was essentially at thermal and compositional equilibrium with local wall rocks. The Quartz-Fuchsite vein is interpreted as an integral part of a progressive wall-rock alteration sequence generated during regional compressive deformation. Early carbonate replacement reaction resulted in a drastic reduction of permeability in the komatiite. As a consequence, the vertical hydrothermal fluid flow became progressively confined to the less reactive quartz-feldspar porphyries, and a high pore fluid pressure regime was built up in the carbonatized komatiite, creating favorable conditions for hydraulic fracture and eraplacement of the Quartz-Fuchsite vein near the slate-komatiite contact. This metasomatically and structurally induced conduit provided a favorable drain for pumping fluids from depth and from adjacent wall rocks. Gold introduction is genetically related to the late fuchsite-pyrite alteration event.