南极东部正长岩花岗岩侵入体地球动力学环境的制约因素

IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
N. V. Borovkov, G. L. Leitchenkov, I. A. Kamenev
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引用次数: 0

摘要

摘要正辉石花岗岩(被称为霞石或霞石系列花岗岩)的特点是二氧化硅和长石矿物含量各不相同,正辉石(超霞石)相是主要的特征性黑云母矿物成分。这些岩石是深海岩石,代表侵入体的一部分,或在二氧化碳不饱和和干燥条件下,在下地壳深处形成自己的火成岩复合体,这可以在任何构造环境中实现。因此,正长岩花岗岩以及来自不同地点的所有类型花岗岩的岩石成因模型足以用于重建某一地区的古地球动力学条件。南极东部地盾的特征是中新生代、晚中新生代-早新新生代和晚新新生代-早古生代时代的造山运动中嵌有阿基坦岩块,由正长岩花岗岩和相关岩石组成的同步和后成因侵入体分布广泛,构成了南极东部造山运动的重要组成部分。根据罗迪尼亚、潘诺提亚和冈瓦纳超大陆的古地球动力学重建,南极东部盾构代表了超大陆地壳的一个重要部分。南极东部正长岩花岗岩的岩石成因模型是任何超大陆古地球动力学重建的基础。我们收集了属于一定时代造山运动的正长岩花岗岩侵入体的构造地质学、构造学和地质年代学数据,并结合地球化学数据绘制了主要元素和稀有元素构造判别图,还分析了 Sm-Nd 同位素系统数据。与造山运动密切相关的南极东部正长岩花岗岩的岩浆来源特征被确定为黑云母下地壳、上地壳和幼地幔物质的组合,其混合比例因造山运动类型而异。研究发现,与中新生代和晚中新生代-早新元古代造山运动有关的正长岩花岗岩形成于长生碰撞的不同阶段,从海洋-大陆型转变为大陆-大陆型;而晚新元古代-早古生代正长岩花岗岩则产生于碰撞后的构造环境中。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Constraints on Geodynamic Setting of East Antarctic Orthopyroxene Granitoids Intrusions

Constraints on Geodynamic Setting of East Antarctic Orthopyroxene Granitoids Intrusions

Abstract

Orthopyroxene granitoids (designated as charnockites or granitoids of the charnockite series) are characterized by varying silica and felsic mineral content, with the orthopyroxene (hypersthene) phase as the main characteristic mafic mineral component. These rocks are abyssal and represent parts of intrusions or form their own igneous complexes at the depth of the lower crust under CO2-undersaturated and dry conditions, which can be achieved within any tectonic setting. Therefore, petrogenetic models for orthopyroxene granitoids as well as for all types of granitoids from different locations are sufficiently applicable for a reconstruction of paleogeodynamic conditions in a certain region. The East Antarctic shield is characterized by Archean blocks embedded within orogens of Mesoproterozoic, Late Mesoproterozoic‒Early Neoproterosoic and Late Neoproterosoic‒Early Paleozoic age, and syn- and post-orogenic intrusions composed of orthopyroxene granitoids and related rocks are widely spread and form a prominent volume of the East Antarctic orogens. According to paleogeodynamic reconstructions of Rodinia, Pannotia and Gondwana supercontinents the East Antarctic shield represents a significant volume of supercontinents’ crust. Petrogenetic models for East Antarctic orthopyroxene granitoids became fundamental for any paleogeodynamic reconstractions of supercontinents. We collected structural geology, tectonics, and geochronology data for orthopyroxene granitoid intrusions belonging to orogens of certain age and combined with the plotting of geochemical data in major and rare element tectonic discrimination diagrams, also analyzed the Sm‒Nd isotope system data. The East Antarctic orthopyroxene granitoids tightly related to orogens are characterized by magmatic sources determined as combination of mafic lower crust, upper crust and juvenile mantle materials mixing up in different proportions depending on type of orogeny. It was established that orthopyroxene granitoids related to Mesoproterozoic and Late Mesoproterozoic‒Early Neoproterosoic orogens formed at different stages of long-lived collision transforming from ocean‒continent to continent‒continent types whereas Late Neoproterosoic‒Early Paleozoic orthopyroxene granitoids arose in post-collision tectonic setting.

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来源期刊
Geotectonics
Geotectonics 地学-地球化学与地球物理
CiteScore
1.90
自引率
9.10%
发文量
28
审稿时长
3 months
期刊介绍: Geotectonics publishes articles on general and regional tectonics, structural geology, geodynamics, and experimental tectonics and considers the relation of tectonics to the deep structure of the earth, magmatism, metamorphism, and mineral resources.
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