Structural Setting and Shape Analysis of Nickel Sulfide Shoots at the Kambalda Dome, Western Australia: Implications for Deformation and Remobilization
Structural Setting and Shape Analysis of Nickel Sulfide Shoots at the Kambalda Dome, Western Australia: Implications for Deformation and Remobilization
复制标题
西澳大利亚坎巴尔达圆顶硫化镍射流的结构设置和形状分析：对变形和再活动的影响
DOI：
10.2113/gsecongeo.100.7.1441
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发表时间：
2005
期刊：
影响因子：
5.8
通讯作者：
N. Archibald
中科院分区：
文献类型：
--
作者：
W. Stone;S. Beresford;N. Archibald
综合三维构造研究对西澳大利亚太古代坎巴尔达穹隆与变科马提岩有关的岩浆硫化镍矿枝分布的地质控制有了新的认识。勘探模型强调深海湾（槽结构）中的火山通道，这些通道在湍流熔岩流的底部受到热侵蚀。然而，对坎巴尔达勘探数据库的三维模型的分析揭示了与区域变形序列D1至D4一致的矿石射击规模控制。D1设置中的矿石笋（例如，Ken shoot）被转换成北-西北D1趋势，并具有不对称的槽结构，其上倾边缘凹入，表明运动方向与坎巴尔达圆顶相反。D2设置中的矿石笋（例如，Lunnon shoot）具有由低角度逆冲断层约束的不对称槽状构造，这表明了圆顶上典型的运动感，矿石逆冲运动进入滑石和碳酸盐岩挂壁岩，缺乏主要的火成岩特征（例如，McMahon Shoot）。D3背景中的矿芽被正断层所抵消，正断层在坎巴尔达圆顶的南端承载金矿化（例如，亨特射击）或在圆顶北端的主要逆断层（例如，Otter-Juan shoots）。D4背景下的矿体（Fisher矿体）从北-西北走向转换为北-北-东北D4走向。相反，与浅的、边界不清的槽状构造有关的矿枝，有或没有显示残余火成岩特征的蛇纹化上盘（例如，杜金拍摄），表明保存火山控制。
火山和构造控制的范围表明，坎巴尔达矿柱从火山控制的端部成员（3个矿柱位于浅槽结构中，具有残余火成岩特征）到结构改造（7个矿柱位于深槽结构中，不具有残余特征）再到结构控制的端部成员（1个矿柱构造侵位在上盘，具有变形特征）的连续体。三维模型的形状分析表明，构造改造和控制的矿芽呈扁长形，其中两个火山控制的矿芽呈扁球形。长形的形状与应变指示器的形状的比较揭示了收缩D1变形在延长矿枝中的重要性，特别是在坎巴尔达圆顶的南北两端。扁圆形火山控制的端部成员反映了邻近主要断裂带的低应变环境。以前的实验系统的比较表明，矿石芽和变质科马提岩变形优先韧性流动。变形对坎巴尔达穹隆硫化镍分布的重要控制作用意味着勘探坎巴尔达式矿化应考虑容矿岩的变形历史。
Integrated three-dimensional structural studies have led to new insights into the geologic controls on the distribution of magmatic nickel sulfide ore shoots associated with metakomatiites at the Archean Kambalda dome, Western Australia. Exploration models emphasize volcanic channels in deep embayments (trough structures) modified by thermal erosion at the base of turbulent lava flows. However, analysis of three-dimensional models of the Kambalda exploration database reveals ore shoot-scale controls consistent with the regional deformation sequence D1 to D4. Ore shoots in D1 settings (e.g., Ken shoot) are transposed into the north-northwest D1 trend and have asymmetric trough structures with reentrant updip margins indicating a sense of movement opposite to that on the Kambalda dome. Ore shoots in D2 settings (e.g., Lunnon shoot) have asymmetric trough structures bound by low-angle thrusts indicating a sense of movement typical of that on the dome, with thrust movement of ore into the talc and carbonated hanging-wall rocks lacking primary igneous features (e.g., McMahon shoot). Ore shoots in D3 settings are offset by normal faults which host gold mineralization at the south end of the Kambalda dome (e.g., Hunt shoot) or by major reverse faults at the north end of the dome (e.g., Otter-Juan shoots). Ore shoots in D4 settings (Fisher shoot) are transposed from the north-northwest trend into the north to north-northeast D4 trend. In contrast, ore shoots associated with shallow, poorly defined trough structures, with or without serpentinized hanging wall showing relict igneous features (e.g., Durkin shoot), indicate preserved volcanic control.
The spectrum of volcanic and structural controls indicates a continuum of Kambalda ore shoots from a volcanic controlled end member (3 shoots in shallow trough structures with relict igneous features) through structurally modified (7 shoots in deep trough structures without relict features) to a structurally controlled end member (1 shoot tectonically emplaced in the hanging wall with deformation features). Shape analysis of the three-dimensional models indicates that the structurally modified and controlled ore shoots have prolate shapes and two of the volcanic controlled ore shoots have oblate shapes. Comparison of the prolate shapes with the shapes of strain indicators reveals the importance of constrictional D1 deformation in elongation of the ore shoots, particularly at the north and south ends of the Kambalda dome. The oblate volcanic-controlled end members reflect low-strain settings adjacent to major fault zones. Comparisons to previous experimental systems suggest that the ore shoots and metakomatiite deformed preferentially by ductile flow. The importance of deformation controls on nickel sulfide distribution at the Kambalda dome means that exploration for Kambalda style mineralization should take into consideration the deformation history of terranes that host ore.