Litholog and structure of the Grenville-aged (≈1.1 Ga) basement of heimefrontfjella (East Antarctica)
Litholog and structure of the Grenville-aged (≈1.1 Ga) basement of heimefrontfjella (East Antarctica)
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heimefrontfjella（南极洲东部）格伦维尔年龄（约 1.1 Ga）基底的岩性和结构
DOI：
10.1007/bf02440112
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
K. Weber
中科院分区：
文献类型：
--
作者：
J. Jacobs;W. Bauer;G. Spaeth;R. J. Thomas;K. Weber
东南极洲的Heimefrontfjella山脉主要由Grenville年龄（约1.1 Ga）的岩石组成，这些岩石在1500 Ma的泛非造山运动期间被改造。三个不连续边界的格伦维尔年龄的火山岩已被确认为（从北到南）Kottas，Sivorg和Vardekkirane火山岩。岩石包含自己的特征岩性组合，虽然每个都是由一个早期的表壳序列的变火山岩和/或变沉积片麻岩，侵入各种（主要是花岗岩类）套房。这些古老的片麻岩的原岩沉积在更古老的基底上，但没有得到确认。在每一个花岗岩中，年龄从1150 ~ 1000 Ma的各种深成岩套侵入较老的层状片麻岩。Vardekenchanese变质基性岩中含有丰富的紫苏辉石岩和二辉麻粒岩相共生体，而Sivorg和Kottas变质基性岩则变质为角闪岩相。P-T估计表明，变质作用的高峰期从南部8千巴的600°C变化到北方Sivorg Güe的4千巴的700 °C。高级组合的区域绿片岩退变质作用可能是泛非时代的。Heimefrontfjella火山岩在1.1Ga的一个复杂而漫长的东西向碰撞造山过程中，在一个平移机制中并置和普遍变形。这表现为早期的缓倾逆冲相关剪切组构（D1），随后是一个重要的（D2）陡右旋剪切带（Heimefront剪切带，HSZ）的开始，在此期间，早期组构和构造变陡并在逆冲方向上旋转。HSZ是一个曲线结构，从北部的右旋斜向走滑侧向坡道转变为南部的陡峭倾滑正面坡道，在那里它形成了Sivorg地体和Vardeklettane地体之间的边界。泛非事件表现为离散的，低至中温韧性脆性剪切（D3）和众多的K/Ar冷却年龄。
The Heimefrontfjella mountains, Western Dronning Maud Land (East Antarctica), are dominantly composed of Grenville-aged (≈ 1.1 Ga) rocks, which were reworked during the Pan -African orogeny at ≈500 Ma. Three discontinuity-bounded Grenville-aged terranes have been recognized namely (from north to south) the Kottas, Sivorg and Vardeklettane terranes. The terranes contain their own characteristic lithological assemblages, although each is made up of an early supracrustal sequence of metavolcanic and/or metasedimentary gneisses, intruded by various (predominantly granitoid) suites. No older basement upon which the protoliths of these older gneisses were deposited has been recognized. In each terrane the older layered gneisses were intruded by various plutonic suites ranging in age from ≈ 1150 to ≈1000 Ma. The Vardeklettane terrane is characterized by abundant charnockites and two-pyroxene granulite facies parageneses in metabasites, whereas the Sivorg and Kottas terranes were metamorphosed to amphibolite facies grade. P-T estimates show that peak metamorphic conditions changed from ≈600°C at 8 kbar in the south, to ≈700 °C at 4 kbar in the northern Sivorg terrane. Regional greenschist retrogression of high-grade assemblages may be of Pan-African age. The Heimefrontfjella terranes were juxtaposed and pervasively deformed during a complex and protracted period of E-W collision orogenesis in a transpressive regime at ≈ 1.1 Ga. This is manifest as early, gently dipping thrust-related shear fabrics (D1), succeeded by the initiation of an important (D2) steep dextral shear zone (Heimefront shear zone, HSZ), during which the early fabrics and structures were steepened and rotated in an anticlockwise sense. The HSZ is a curvilinear structure which changes from a dextral oblique strike-slip lateral ramp in the north to a steep dip-slip frontal ramp in the south, where it forms the boundary between the Sivorg and Vardeklettane terranes. The Pan-African event is manifested as discrete, low- to medium-temperature ductile to brittle shears (D3) and numerous K/Ar cooling ages.