鲁西地区地质构造特征及其形成机制
Structure in western Shandong and its genetic mechanism
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摘要: 提要：根据区域地层(体)中部老外部新的环状分布，断裂构造的环状、放射状展布，核部缓倾拆离滑脱构造的发育特点，幔源岩浆活动以及区域岩石学、岩石化学、同位素地质学等方面的研究，探讨了鲁西幔枝构造特征及其形成机制。研究认为鲁西地区北西向陡倾韧性剪切带切割了深部华北地幔亚热柱向外拆离的地幔岩，导致其减压释荷形成深熔岩浆。岩浆演化序列表现出岩浆基性程度由高变低、侵入深度由深变浅、围岩蚀变由强变弱的总体演化趋势。由于强烈的岩浆上侵使得变质基底隆升、盖层拆离滑脱，形成典型的鲁西幔枝构造，在顶部则发育一系列明显的拆离掀斜断块。Abstract: Abstract: The structural characteristics of the western Shandong mantle branch and its genetic mechanism are discussed according to the outward-younging ring distribution of the strata, ring faults and radial faults, gently dipping detachments and mantle-derived magmatism, as well as regional petrology, petrochemistry and isotope geology. These studies suggest that the NW-trending, steeply dipping ductile shear belt cuts deep-seated pyrolite of the mantle sub-plume beneath North China, resulting in depressurizing and load-releasing to form anatectic magma. The magmatic evolutionary series shows a general trend of evolution from high to low basicity of magma, from great to shallow depths of magmatic intrusion and from strong to weak wall-rock alteration. Strong magmatic intrusion resulted in the uplift of the metamorphic basement and detachment of the cover, thus forming the typical western Shandong mantle branch structure. A number of obviously detached, tilted fault blocks are developed on top of this mantle branch.
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Keywords:
- hot mantle plume /
- mantle branch /
- structural evolution /
- forming mechanism /
- western Shandong area
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