The Cleaverville Group in the West Pilbara Coastal Granitoid-Greenstone Terrain of Western Australia: An example of a Mid-Archaean immature oceanic island-arc succession
The Cleaverville Group in the West Pilbara Coastal Granitoid-Greenstone Terrain of Western Australia: An example of a Mid-Archaean immature oceanic island-arc succession
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西澳大利亚西皮尔巴拉沿海花岗岩-绿岩地形的克利弗维尔群：中太古宙未成熟海洋岛弧序列的一个例子
DOI：
10.1016/s0301-9268(97)00066-1
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发表时间：
1998
影响因子：
3.8
通讯作者：
A. Taira
中科院分区：
文献类型：
--
作者：
S. Kiyokawa;A. Taira
4400米厚的火山沉积序列形成了3200-3000年前的克利弗维尔群，沿着西澳大利亚西北部皮尔巴拉的西海岸线保存完好。两个岩性组合。在克利弗维尔群中发现了火山岩组合和化学-火山-沉积岩组合。火山岩组合厚度约3300米，主要由枕状玄武岩和流纹岩组成。化学-火山沉积岩组合至少有1100米厚，由化学成因沉积岩(硅质岩和条带状铁建造)和火山沉积岩(粗粒和细粒凝灰岩)组成。从克利弗维尔群显示的地层模式中识别出三个火山沉积旋回。每个旋回都包括一次玄武岩火山作用的初始阶段，然后是流纹岩火山作用，然后是化学成因沉积作用。玄武岩、流纹岩和化学成因沉积岩的每个旋回包之间的边界是整合面。火山岩的厚度相对于化学成因的沉积岩，在每一套中都是向上递减的。火山岩在每个组合中所占比例的向上降低，表明沉积地点的双峰式火山活动随着时间的推移而强度降低。玄武岩主要是非孔洞的，而化学成因的沉积岩是非常精细的层理，缺乏大陆起源的证据。这些特征表明，克利弗维尔群沉积在近海，可能是深海环境。蜥蜴山组位于克利弗维尔群的一个角度不整合之上。该地层记录了西皮尔巴拉海岸花岗岩-绿岩地带首次出现大陆成因的沉积岩。大洋环境下双峰式火山作用及其伴生火山沉积的旋回记录表明，克利弗维尔群起源于类似于现代未成熟大洋岛弧的构造环境。此外，来自大陆的蜥蜴山组沉积岩可能记录了一次弧-陆碰撞事件。
The 4400 m-thick volcanosedimentary succession that forms the 3200-3000 yr-old Cleaverville Group is well-preserved along the western coastline of the Pilbara in northwestern Western Australia. Two lithological assemblages. namely the Volcanic Rock Assemblage and the Chemical-Volcanosedimentary Rock Assemblage, are identified in the Cleaverville Group. The Volcanic Rock Assemblage is approximately 3300 m-thick, and consists mainly of pillow basalt and rhyolitic flow rocks. The Chemical-Volcanosedimentary Rock Assemblage, which is at least 1100 m-thick, comprises chemogenic sedimentary rocks (chert and banded iron formation) and volcanosedimentary rocks (coarse and fine grained tuffs). Three volcanosedimentary cycles have been recognized from stratigraphic patterns displayed by the Cleaverville Group. Each cycle involved an initial episode of basaltic volcanism that was followed by rhyolitic volcanism, and then by chemogenic sedimentation. Boundaries between each cyclic package of basalt, rhyolite and chemogenic sedimentary rocks are conformable surfaces. The thickness of volcanic rocks, relative to chemogenic sedimentary rocks, within each package, decreases upwards within the succession. The upward decrease in the proportion of volcanic rocks in each package, suggests that bimodal volcanic activity, at the depositional site, decreased in intensity through time. Basalts are primarily non-vesicular, whereas chemogenic sedimentary rocks are very finely laminated and lack evidence of continental derivation. These features imply that the Cleaverville Group was deposited in an offshore, probably deep-sea environment. The Lizard Hills Formation lies above an angular unconformity on the Cleaverville Group. The formation records the first appearance, in the West Pilbara Coastal Granitoid-Greenstone Terrain, of sedimentary rocks that are of a continental origin. The cyclic record of bimodal volcanism, and accompanying volcanogenic sedimentation, within an oceanic setting suggests that the Cleaverville Group originated in a tectonic environment similar to a modern immature oceanic island-arc. Furthermore, it is possible that continentally derived sedimentary rocks of the Lizard Hills Formation record an arc-continent collision event.