华北克拉通北缘中段龙王庙岩体和上庄岩体的岩石成因及构造指示
发布时间：2018-07-29 17:29
【摘要】：华北克拉通北缘中段的大陆岩石圈地幔在奥陶纪 三叠纪时逐步在蒙古洋板块多阶段俯冲的影响下变得活跃。本文选取的龙王庙岩体和上庄岩体的形成时代分别是~399 Ma和~123?128 Ma,属于中泥盆世和早白垩世。本文在重点论述二者岩石学成因和构造指示意义的基础上,结合前人对华北克拉通北缘中段二者时间区间的其他岩体研究,最后综合论述晚古生代到晚中生代华北克拉通北缘中段岩石圈地幔在中生代大规模减薄之前的构造演化过程。主要取得的成果和创新性认识如下:1、龙王庙岩体同时具备弧和后碰撞的地化特征,是弧挤压到弧后伸展过渡环境的产物,其弧后伸展环境对应的弧 陆碰撞是晚志留世的白乃庙岛弧体与华北克拉通北缘的碰撞。与同时期的红石砬和二道沟?下哈叭沁杂岩体比较,可以得出该阶段的大陆岩石圈地幔并没有受到蒙古洋系统大规模的影响,仅表现为大陆岩石圈地幔的不均一富集。2、上庄岩体的形成时代与华北克拉通中部和东部中生代岩石圈减薄机制下的伸展作用事件吻合。母岩浆等同的细粒辉长岩地化特征(比如低Dy/Yb值:3.48?3.55;La/Yb值:50.83?53.22)显示其来源为含尖晶石二辉橄榄岩相岩石圈富集地幔的部分熔融,且它们的Zr/Nb(8.03?9.09),Zr/Y(13.0?15.1)和Nb/Y(1.62?1.66)值显示源区有少量软流圈地幔等深部物质的加入。软流圈上涌带来足够热量,加上同时期源于太平洋板片俯冲而来的水份,共同促成上庄岩体母岩浆的形成。太平洋俯冲板片给北缘的大陆岩石圈地幔提供了一定的水份,但没有造成该区域大陆岩石圈地幔的进一步富集。3、综合华北克拉通北缘其他阶段的基性-超基性岩体以及其他幔源岩体的各种特征,得出华北克拉通北缘的大陆岩石圈地幔在遭受中生代大规模的岩石圈破坏和减薄事件之前,曾受蒙古洋板块阶段性俯冲的影响。它们的Hf同位素和地化特征表明大陆岩石圈地幔总体表现为越来越富集。4、在蒙古复合地体与华北克拉通北缘于晚二叠世发生碰撞后,北缘受到后碰撞/后造山作用,引起岩石圈的拆沉,随即出现的基性-超基性岩体兼具软流圈地幔和岩石圈地幔的混合特征。而后这一拆沉作用逐步向克拉通内部发展,引起更大规模的岩石圈拆沉作用,以华北克拉通内部出现大规模的晚侏罗世(~160 Ma)高镁安山岩、英安岩和埃达克岩达到顶峰。上庄岩体表明早白垩世时期北缘岩石圈破坏和减薄的机制是热/化学侵蚀。
[Abstract]:The continental lithospheric mantle of the northern margin of the North China Craton became active during the Ordovician Triassic under the influence of multi-stage subduction of the Mongolian oceanic plate. The age of formation of the Longwangmiao and Shangzhuang pluton in this paper is 399Ma and 123128Marespectively, belonging to the Middle Devonian and early Cretaceous. Based on the emphases on the petrogenesis and tectonic indication of the two rocks, this paper studies other rock masses in the time interval of the northern margin of the North China Craton in combination with previous studies. Finally, the tectonic evolution of the lithospheric mantle in the northern margin of the North China Craton from the late Paleozoic to the late Mesozoic before the large-scale thinning of the Mesozoic is comprehensively discussed. The main achievements and innovative understandings are as follows: 1. The Longwangmiao rock mass has geochemistry characteristics of both arc and rear collision, which is the product of the transition environment from arc compression to back-arc extension. The arc-continent collision corresponding to its back-arc extensional environment is a collision between the late Silurian Bainaimiao island arc body and the northern margin of the North China Craton. With the same period of Hongshila and Erdaogou? A comparison of the Lower Hapeqin complex shows that the continental lithospheric mantle at this stage was not affected by the Mongolian oceanic system on a large scale. The formation age of the Shangzhuang rock body coincides with the extensional events under the Mesozoic lithospheric thinning mechanism in the central and eastern North China Craton. The geochemical characteristics of the mother magma equivalent fine-grained gabbro (for example, low Dy/Yb value: 3.48 ~ 3.55 / Lap / Yb = 50.83 / 53.22) indicate that it originated from the partial melting of the mantle enriched by the lithospheric lithosphere containing spinel. Their Zr/Nb (8.03 ~ 9.09) and Nb/Y (1.62 ~ 1.66) values indicate that a small amount of deep materials such as the asthenospheric mantle are added into the source region. The upwelling of the asthenosphere brought enough heat together with the water from the Pacific plate subduction in the same period which contributed to the formation of the mother magma of the Shangzhuang rock mass. The Pacific subduction plate provides a certain amount of water to the continental lithospheric mantle in the northern margin. However, it has not resulted in further enrichment of the continental lithospheric mantle in the region, and the various characteristics of the basic-ultrabasic rock bodies and other mantle-derived rocks in other stages of the northern margin of the North China Craton have been synthesised. It is concluded that the continental lithospheric mantle in the northern margin of the North China Craton was affected by the stage subduction of the Mongolian ocean plate before the Mesozoic large-scale lithospheric destruction and thinning events. Their HF isotopic and geochemical characteristics indicate that the continental lithospheric mantle is more and more enriched in general. After the collision between the Mongolia composite terrane and the North China Craton occurred in the late Permian, the northern margin was subjected to post-collision / post-orogeny. The basic-ultrabasic rock body, which caused the lithosphere to desink, has the mixed characteristics of the asthenospheric mantle and the lithospheric mantle. Then the desinking gradually developed to the interior of the craton, resulting in a larger lithospheric desubsidence, with the large scale late Jurassic (160Ma) high mafic andesite within the North China craton, with the dolomite and adakite reaching its peak. The Shangzhuang rock mass indicates that thermal / chemical erosion was the mechanism of lithospheric destruction and thinning in the northern margin of early Cretaceous.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P581;P542
，
本文编号：2153457
[Abstract]:The continental lithospheric mantle of the northern margin of the North China Craton became active during the Ordovician Triassic under the influence of multi-stage subduction of the Mongolian oceanic plate. The age of formation of the Longwangmiao and Shangzhuang pluton in this paper is 399Ma and 123128Marespectively, belonging to the Middle Devonian and early Cretaceous. Based on the emphases on the petrogenesis and tectonic indication of the two rocks, this paper studies other rock masses in the time interval of the northern margin of the North China Craton in combination with previous studies. Finally, the tectonic evolution of the lithospheric mantle in the northern margin of the North China Craton from the late Paleozoic to the late Mesozoic before the large-scale thinning of the Mesozoic is comprehensively discussed. The main achievements and innovative understandings are as follows: 1. The Longwangmiao rock mass has geochemistry characteristics of both arc and rear collision, which is the product of the transition environment from arc compression to back-arc extension. The arc-continent collision corresponding to its back-arc extensional environment is a collision between the late Silurian Bainaimiao island arc body and the northern margin of the North China Craton. With the same period of Hongshila and Erdaogou? A comparison of the Lower Hapeqin complex shows that the continental lithospheric mantle at this stage was not affected by the Mongolian oceanic system on a large scale. The formation age of the Shangzhuang rock body coincides with the extensional events under the Mesozoic lithospheric thinning mechanism in the central and eastern North China Craton. The geochemical characteristics of the mother magma equivalent fine-grained gabbro (for example, low Dy/Yb value: 3.48 ~ 3.55 / Lap / Yb = 50.83 / 53.22) indicate that it originated from the partial melting of the mantle enriched by the lithospheric lithosphere containing spinel. Their Zr/Nb (8.03 ~ 9.09) and Nb/Y (1.62 ~ 1.66) values indicate that a small amount of deep materials such as the asthenospheric mantle are added into the source region. The upwelling of the asthenosphere brought enough heat together with the water from the Pacific plate subduction in the same period which contributed to the formation of the mother magma of the Shangzhuang rock mass. The Pacific subduction plate provides a certain amount of water to the continental lithospheric mantle in the northern margin. However, it has not resulted in further enrichment of the continental lithospheric mantle in the region, and the various characteristics of the basic-ultrabasic rock bodies and other mantle-derived rocks in other stages of the northern margin of the North China Craton have been synthesised. It is concluded that the continental lithospheric mantle in the northern margin of the North China Craton was affected by the stage subduction of the Mongolian ocean plate before the Mesozoic large-scale lithospheric destruction and thinning events. Their HF isotopic and geochemical characteristics indicate that the continental lithospheric mantle is more and more enriched in general. After the collision between the Mongolia composite terrane and the North China Craton occurred in the late Permian, the northern margin was subjected to post-collision / post-orogeny. The basic-ultrabasic rock body, which caused the lithosphere to desink, has the mixed characteristics of the asthenospheric mantle and the lithospheric mantle. Then the desinking gradually developed to the interior of the craton, resulting in a larger lithospheric desubsidence, with the large scale late Jurassic (160Ma) high mafic andesite within the North China craton, with the dolomite and adakite reaching its peak. The Shangzhuang rock mass indicates that thermal / chemical erosion was the mechanism of lithospheric destruction and thinning in the northern margin of early Cretaceous.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P581;P542
，
本文编号：2153457
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