Delineating the Exmouth mantle plume (NW Australia) from denudation and magmatic addition estimates
Delineating the Exmouth mantle plume (NW Australia) from denudation and magmatic addition estimates
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根据剥蚀和岩浆添加估计描绘埃克斯茅斯地幔柱（澳大利亚西北部）
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发表时间：
2015
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通讯作者：
M. Rohrman
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作者：
M. Rohrman
火山边缘是一类大型火成岩省（LIP），其特征是裂谷衍生的玄武岩岩浆作用。这通常归因于与伸展相关的岩石圈减薄，产生减压熔融。影响火山边缘岩浆作用的另一个机制是地幔柱引起的岩石圈减薄。不幸的是，很难区分这些机制，因为它们似乎几乎同时发生。裂谷火山边缘会产生线性剥蚀和岩浆添加模式，而地幔柱或活跃的上升流会产生更多的亚圆形穹窿模式。在这里，我使用岩浆添加和剥蚀模式来区分澳大利亚西北部近海火山边缘数据集中的这些场景。地震和井数据结果表明存在用于描绘晚侏罗世埃克斯茅斯地幔柱的穹顶成分。这种上升流以高度延伸和下沉的大陆碎片为中心，该大陆碎片以现今海底索纳海脊和索尼亚海脊为界，包括居维叶边缘和开普岭断裂带。该地区的特征是约 2.6 公里的剥蚀和约 500 米的构造隆起，侵蚀产物是早白垩世下巴罗三角洲的源物质。剥蚀分析表明，地震检测到的板下岩浆中只有约 40% 与熔融有关，板下有效厚度在隆起处附近约 4 公里，而在外部区域则减小。构造沉降分析、地震地层学和板块重建表明，羽流引起的穹顶隆起先于岩浆作用和破碎。羽流活动之后是一条向西传播的热点轨迹，可能终止于大印度（现西藏）。
Volcanic margins are a class of large igneous provinces (LIPs) characterized by rifting-derived basaltic magmatism. This is commonly attributed to extension-related lithospheric thinning, generating decompression melting. Another mechanism influencing magmatism on volcanic margins is mantle plume–induced lithospheric thinning. Unfortunately, it is difficult to differentiate between these mechanisms because they seem to take place almost contemporaneously. Whereas rifted volcanic margins produce linear denudation and magmatic addition patterns, mantle plumes or active upwellings would generate more subcircular domal patterns. Here, I use magmatic addition and denudation patterns to discriminate between these scenarios in a data set from the volcanic margin offshore NW Australia. Seismic and well data results suggest the presence of a domal component that is used to delineate the Late Jurassic Exmouth mantle plume. This upwelling was centered on a highly extended and subsided continental fragment bounded by the present-day subsea Sonne and Sonja Ridges and includes the Cuvier margin and Cape Range fracture zone. The region is characterized by ∼2.6 km of denudation and ∼500 m of tectonic uplift, with erosion products acting as source material for the Early Cretaceous Lower Barrow delta. Denudation analysis indicates that only ∼40% of the seismically detected magmatic underplate is melt related, with the effective underplate ∼4 km thick near the locus of uplift and decreasing in the outer regions. Tectonic subsidence analysis, seismic stratigraphy, and plate reconstruction suggest that the plume-induced domal uplift preceded magmatism and breakup. Plume activity was followed by a westward-propagating hotspot track, possibly terminating in Greater India (present Tibet).