镁铁岩脉侵位机制及伴随变形

MAFIC DYKE EMPLACEMENT MECHANISM AND ACCOMPANYING DEFORMATION

南澳的ＥＹＲＥ半岛位于ＧＡＷＬＥＲ克拉通南部，包含了ＧＡＷＬＥＲ克拉通太古界至中元古界结晶基底的主要部分。全区于１４２３Ｍａ克拉通化，此后除了局部的，较小的地壳运动外，一直是稳定的克拉通地块。研究区ＪＵＳＳＩＥＵ半岛为ＥＹＲＥ半岛南部的次级半岛，镁铁岩脉群以及韧性剪切糜棱岩带主要沿海岸分布。区内出露岩石变形复杂，脉岩强烈的布丁化并重结晶，围岩中的转换拉伸构造及转换挤压构造可追踪识别。基性岩浆的侵位是转换拉伸力和岩浆压力联合作用的结果，脉岩群的传播侵位（ＰＲＯＰ－ＡＧＡＴＩＯＮ）与转换拉伸作用（ＴＲＡＮＳＴＥＮＳＩＯＮ）密切相关。多次的转换拉伸与挤压作用，还导致镁铁岩脉边缘成为高应变带，并形成复杂的变形图案。此外，围岩中伴随的变形以次剪切带（ＳＵＢＳＨＥＡＲＺＯＮＥ）最为显著，是作动力学分析最好的匹配构造。

The Eyre Peninsula,South Australia,makes up the southern part of the Gawler Craton.It contains a major portion of Archean to mid Proterozoic crystalline basement province of the Gawler Craton.It is a region which,except minor,localized movements,has been a reasonably stable platformal area since it was stabilized before 1423 Ma.The north eastern parts of the craton are unconformably overlain by Late proterozoic and Cambrian platform sediments deposited on the Suart Shelf.The Adelaide Geosyncline,which now forms the Delamarian Fold Belt,provides the north eastern boundary for the Gawler Craton and the Suart shelf.The eastern boundary developed between 800-490 Ma and is actually delineated by the Torrens Hinge Zone.The Gawler Craton has been subjected to substantial extension 2000 Ma.This formed a sedimentary basin into which to Hutchison Group was deposited.The Kimban Orogeny (1840-1550 Ma) was associated with intrusive magmatism and deformed the new intrusives,the Hutchison Group and the underlying basement.The Paleoproterozoic Kimban mobile belt was exposed in the study area and divides the area into two contrasting crustal terrains juxtaposed by the Kalinjala Shear Zone.The western terrain consists of the Hutchison Group meta sediments (1964-1845Ma),meta basics and meta volcanics,and the Moody Granitoid Suite (1740-1700Ma).The Hutchison Group unconformably overlies the older Sleaford Complex which was affected by the Sleafordian Orogeny (2600-2400 Ma) as well as the Kimban Orogeny.The eastern terrain essentially consists of a batholith,here referred to as the Lincoln Batholith,composed of the Donington Granitoid Suite (1850-1843 Ma),mafic dykes that syn plutonic with the Donington Granitoid Suite,and the Colbret Granitoid Suite.The Lincoln Batholith is intruded by the Tournefort mafic dyke suite. The mafic dykes and the mylonite in Jussieu Peninsula are mainly exposed along the coastal section.Although they are deformed,boudinaged and recrystallized,their development in an environment of transtensional and transpressional tectonic settings can still be recognized.By using transfer geometry,we can explain the propagation and intrusion of the mafic dykes,the deformation along the mafic dyke boundaries,and localization of deformation that formed the ductile mylonite zone.