| 南天山北缘麻粒岩残迹与辉石相韧性变形研究 |
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| 引用本文： | 舒良树,王赐银.南天山北缘麻粒岩残迹与辉石相韧性变形研究[J].地质科学,1996,31(4):375-383. |
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| 作者姓名： | 舒良树 王赐银 |
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| 作者单位： | 南京大学地球科学系, 南京 210093 |
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| 基金项目： | 国家自然科学基金,批准号4937201 |
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| 摘 要： | 对新疆北部南天山北缘蛇绿混杂岩带中麻粒岩的岩石学、矿物学、岩石化学、矿物化学、稀土元素地球化学特征及辉石相韧性变形构造的研究表明,榆树沟麻粒岩的共生矿物组合为透辉石-次透辉石-紫苏辉石-石榴石-斜长石,属基性岩类暗色麻粒岩,以低硅高钙为特征,稀土总量低,轻稀土与铕弱亏损,反映高温高压熔融环境和岩浆分异差的特点。麻粒岩及超镁铁岩中的辉石经历了强烈的韧性剪切变形作用,不对称辉石残斑系、动态重结晶辉石亚颗粒集合体、辉石变形双晶纹、鱼尾构造、核幔构造等显微韧变构造广泛发育。宏观和微观运动学分析揭示了一期从南向北的推覆构造。麻粒岩的形成与早古生代大陆地壳拉伸作用有关,辉石相韧性变形则与早古生代末南天山边缘海的挤压关闭和推覆逆冲有关。
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| 关 键 词： | 辉石相韧性变形 基性岩类麻粒岩 南天山北缘 早古生代 |
| 收稿时间： | 1995-12-18 |
| 修稿时间： | 1995-12-18; |
GRANULITE RELICS AND PYROXENE-FACIES DUCTILE DEFORMATION IN THE NORTHERN BOUNDARY OF THE SOUTHERN TIANSHAN |
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| Shu Liangshu Wang Ciyin Ma Ruishi.GRANULITE RELICS AND PYROXENE-FACIES DUCTILE DEFORMATION IN THE NORTHERN BOUNDARY OF THE SOUTHERN TIANSHAN[J].Chinese Journal of Geology,1996,31(4):375-383. |
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| Authors: | Shu Liangshu Wang Ciyin Ma Ruishi |
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| Institution: | Department of Earth Sciences, Nanjing University, Nanjing 210093, China |
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| Abstract: | This paper reported the latest research results on the granulite relics and pyroxene-facies ductile deformation that occur in the early Paleozoic ophiolitic melange blocks along the northern boundary of the Southern Tianshan belt, Xinjiang. Studies on Yushugou granulite from field geology, crystal optics, petrochemistry, mineral chemistry and REE geochemistry suggest that the Yushugou granulite is composed of diopsite, salite, hypersthene, garnet and plagjoclase and is named as garnet websterite granulite or basic rock-type granulite, which is characterized by lower SiO2(45.54%), higher CaO(14.83%), lower REE content(65×10-6-90×10-6), LREE /HREE 0.66- 0.91, Eu /Sm 0.34- 0.35 and weakly depletion in Eu, showing a formation environment in lower crust with higher pressure(1.5GPa), higher temperature(813℃)and lower magmatic differentiation. All the granulites are bordered by faults. Our works found that ductile shear structures occur commonly in the pyroxenes of granulite and ultramafic rock, including core-mantle structure, flatten and elongated structure, dynamic recrystallised pyroxene subgrains with orientated arrangement, asymmetric pyroxene porphyroclast system, fish-tail structure, pyroxene pressure shadow and deformed twinning striation, and so on. So, these deformed rocks can be called as pyroxene-facies mylonitic ones. Kinematic analysis indicates a thrust ductile deformation from south to north. The authors propose that the Yushugou granulite formed about 420 Ma in the lower crust was resulted from the early Paleozoic crustal rifting to form the Southern Tianshan marginal sea, and pyroxene-facies ductile deformation that took place about 402 Ma was related to thrusting from deep to shallow due to closure of the marginal sea during the end stage of early Paleozoic, leading to rising of granulite toward upper crust. |
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| Keywords: | Pyroxene-facies ductile deformation Basic rock-type granulite Northern boundary of Southern Tianshan Early Paleozoic |
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