Cordilleran‐type orogeny and episodic growth of continents: Insights from the circum‐Pacific continental margins
Cordilleran‐type orogeny and episodic growth of continents: Insights from the circum‐Pacific continental margins
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DOI：
10.1046/j.1440-1738.1999.00232.x
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发表时间：
1999-06
期刊：
影响因子：
1.5
通讯作者：
T. Tagami;N. Hasebe
中科院分区：
文献类型：
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作者：
T. Tagami;N. Hasebe
基于地质约束和加积楔的力学原理，提出了板块俯冲带造山作用的一种新的物质迁移假说，即所谓的“柯迪亚克型造山作用”。该假说的主要构造过程包括：（1）沿上覆板块边缘沿着的幕式大规模岩浆活动;（2）通过弧前向海沟提供大量的火成岩和侵蚀物质，增加了向海沟的净沉积物流入量;以及（iv）楔体内部物质向上迁移，导致楔体内陆边缘附近高P/T变质岩的折返。这一假设得到了验证的测试使用现有的地质和热年代学数据从两个典型类型的俯冲造山带在日本西南部和加州。这一假说与热年代学观点相结合，要求重新考虑成对变质作用的共演化性。在区域高温高压变质作用的开始和高温高压变质作用的抬升和折返之间，可以观察到时间配对，物质迁移需要一定的时间滞后。因此，在检查时间配对时，应将火成岩和相关的高T/P变质岩的形成年龄与高P/T变质岩的折返年龄进行比较。对于大多数环太平洋大陆边缘而言，触发柯式造山带的幕式、广泛的岩浆活动在白垩纪中期表现出时间相关性。在环太平洋边缘的西部也观察到由此产生的增生复合体的广泛形成。推断的中白垩世环太平洋造山带伴随着大陆地壳生产率的大幅增加，与盘古大陆裂解和中太平洋超级地幔柱事件大致同时代，暗示该造山带是中白垩世地球脉动的一部分。
A new material migration hypothesis for the plate subduction zone orogeny, so‐called ‘the cordilleran‐type orogeny’, is proposed on the basis of geological constraints as well as mechanics of accretionary wedges. The major tectonic processes of the hypothesis comprise: (i) episodic, extensive magmatism along the margin of an overriding plate; (ii) supply of voluminous igneous and eroded materials through forearc to trench, with an increase in the net sediment influx into trench; (iii) accelerated accretion of sediments beneath an overriding older accretionary wedge; and (iv) upward material migration within the wedge and resultant exhumation of high‐P/T metamorphic rocks near the inland margin of the wedge. This hypothesis was validated by the test using available geo‐ and thermo‐chronological data from two classical types of subduction‐related orogens in Southwest Japan and California. The hypothesis, coupled with the thermochronologic point of view, requires the reconsideration of coevality of paired metamorphism. The temporal pairing is to be observed between the beginning of the regional high‐T/P metamorphism and that of the uplift and exhumation of high‐P/T metamorphism, with some time lag needed for material migration. Where the temporal pairing is examined therefore, the formation age of igneous rocks and related high‐T/P metamorphic rocks should be compared to the exhumation age of high‐P/T metamorphic rocks. The episodic, extensive magmatism that triggers the cordilleran‐type orogeny shows a temporal correlation in the mid‐Cretaceous for most circum‐Pacific continental margins. The resultant widespread formation of accretionary complexes is also observed in the western part of the circum‐Pacific margins. The deduced mid‐Cretaceous circum‐Pacific orogeny accompanied a gross increase in the continental crust production rate, and was approximately coeval with the Pangea breakup and the Central Pacific superplume episode, implying the orogeny as a part of the mid‐Cretaceous pulsation of the Earth.