Structural controls on nickel sulphide ore shoots in Archaean komatiite, Kambalda, WA: the volcanic trough controversy revisited
Structural controls on nickel sulphide ore shoots in Archaean komatiite, Kambalda, WA: the volcanic trough controversy revisited
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华盛顿州坎巴尔达太古代科马提岩中硫化镍矿芽的结构控制：重新审视火山槽争议
DOI：
10.1016/j.jsg.2003.11.014
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发表时间：
2004
影响因子：
3.1
通讯作者：
N. Archibald
中科院分区：
文献类型：
--
作者：
W. Stone;N. Archibald
对Kambalda-Tramways地区(西澳大利亚太古宙Yilgarn Craton)广泛勘探数据库的结构评估正在解决一个长期悬而未决的问题，即部分限制硫化镍(NIS)矿体的海槽结构是火山成因还是构造成因。海槽结构为复杂的线状域，与滑石-碳酸盐蚀变叠加在下盘玄武岩之上加厚的科马提岩有关。可识别出两种端元槽形结构类型：(1)可再入槽形结构和(2)开式槽形结构。重入槽构造顶部窄于底部，断面强烈不对称，分布受限于坎巴达穹隆，并侵入和截断矿石。敞开的海槽结构顶部比底部宽，横截面上弱不对称，普遍存在于坎巴达穹顶外，并沿其侧缘矿化。除了与槽伴生的矿石外，其他NIS矿脉覆盖在近平面的科马提岩-玄武岩接触面上，并被具有残留火成岩结构的蛇纹岩覆盖。所有这些特征表明，海槽构造可能反映了区域褶皱冲断过程中岩石接触部位的构造褶皱、增厚和蚀变，标志着不同的能力。因此，NIS勘探战略应考虑到构造和变质特征以及火山学和地层学特征。识别区域背斜和穹隆顶部附近有利的科马提岩-玄武岩地层中与主要能力对比有关的褶皱和逆冲模式，将有助于勘探成功。
Structural evaluation of the extensive exploration database for the Kambalda–Tramways area (Archaean Yilgarn Craton, Western Australia) is addressing the long outstanding issue of whether the trough structure embayments that partly confine the nickel sulphide (NiS) ore shoots are volcanic or tectonic in origin. The trough structures are complex linear domains associated with talc–carbonate alteration overprinting thickened komatiite overlying footwall basalt. Two end-member trough structure types are recognised: (1) re-entrant trough structures, and (2) open trough structures. The re-entrant trough structures are narrower at the top than at the base, strongly asymmetric in cross-section, restricted in distribution to Kambalda Dome, and transgress and truncate ore. The open trough structures are wider at the top than at the base, weakly asymmetric in cross-section, prevalent outside Kambalda Dome, and are mineralised along their lateral margins. In addition to trough-associated ore, other NiS ore shoots overlie near-planar komatiite-basalt contacts and are overlain by serpentinite with relict igneous textures. All these features indicate the possibility that the trough structures reflect structural folding, thickening and alteration at rock contacts marking different competency during regional fold–thrusting. Consequently, NiS exploration strategies should consider structural and metamorphic features, as well as volcanologic and stratigraphic features. Recognition of folding and thrusting patterns related to major competency contrasts in favourable komatiite–basalt stratigraphy near the crest of regional anticlines and domes would aid exploration success.