| 长乐-南澳断裂带晚中生代岩浆活动
与变质-变形关系 |
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| 引用本文： | 舒良树,于津海,王德滋.长乐-南澳断裂带晚中生代岩浆活动
与变质-变形关系[J].高校地质学报,2000,6(3):368-378. |
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| 作者姓名： | 舒良树 于津海 王德滋 |
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| 作者单位： | 南京大学 地球科学系；内生金属矿床成矿机制研究国家重点实验室， 江苏 南京 210093 |
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| 基金项目： | 国家自然科学基金，49632080， |
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| 摘 要： | 长乐-南澳断裂带是东南沿海地区陆内强烈变质-变形带。带内沉积岩、火山岩和早白垩世的钙碱性角闪石黑云花岗岩和花岗闪长岩都已发生可达角闪岩相的变质和石英-长石相韧性剪切变形。鉴于高温矿物和强烈韧性变形多出现在深成岩附近；远离深成岩，变质和变形就逐渐减弱，故本文认为，至少有一部分变质变形的热源是由岩浆提供的。韧剪组构和糜棱质花岗岩是在岩浆侵位的晚期或长乐-南澳断裂带左旋走滑时，在中地壳部位同时形成的，长乐断裂带中花岗岩的组构记录了一期同走滑变形的岩浆作用，“软变形”作用。据此，长乐-南澳带内花岗岩的形成是受走滑剪切应力和岩浆热双重制约的，是在走滑过程中实现的。其动力来源可能与晚中生代的太平洋板块沿日本中央构造线—台湾纵谷带朝东亚陆缘的斜向俯冲有关。
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| 关 键 词： | 花岗岩类 变质－变形 断裂 岩浆活动 晚中生代 |
| 收稿时间： | 2000-09-20 |
| 修稿时间： | 2000-02-22 |
Late Mesozoic Granitic Magmatism and Its Relation to Metamorphism-Ductile Deformation in the Changle-Nan'ao Fault Zone, Fujian Province |
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| SHU Liang-shu,YU Jin-hai,WANG De-zi.Late Mesozoic Granitic Magmatism and Its Relation to Metamorphism-Ductile Deformation in the Changle-Nan''''ao Fault Zone, Fujian Province[J].Geological Journal of China Universities,2000,6(3):368-378. |
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| Authors: | SHU Liang-shu YU Jin-hai WANG De-zi |
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| Institution: | Department of Earth Sciences; State Key Laboratory for Mineral Deposits Research Nanjing University, Nanjing 210093, China |
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| Abstract: | The Changle-Nan'ao fault is an important tectonic zone with s trongly Late Mesozoic granitic magmatism and metamorphism-ductil e shear deformation in the coastal region of Southeastern China. All Pre-Late Cretaceous se dim entary rocks, volcanic and volcanoclastic rocks and Late Cretaceous CA -type hor nblende biotite granite and granodiorite were matamorphosed and deformed to form various amphibolite-facies metamorphic rocks and quartz -feldspar-facies duct ile sheared rocks characterized by penetrative fabrics that are developed well i n the wallrocks and granitc rocks. In this zone, a NE striking sheared foliatio ns are subvertical, strech ing lineations are subhorizontal, and non-coaxial ductile de formed fabrics occu r widespreadly. Kinematic study suggests that this is a sinistral strike -slip d uctile shear zone with slip-down component partly; Late motion sense of dextral strike-slip ductile shear exists locally. Granitic bodie s are distribut ed in the central part of the fault zone. From the center of shear zone to the o uter part, metamorphic grade decreases from amphibolite facies gneiss to greenschist facies phyllite and slate; metamorphic minerals change from sillima nite to garnet, mica and sericite. Mylonization and ductile shear fabrics are al so weakened from the center of ductile shear zone or of granitic body to the ou ter parts. Many small-scale ductile deformed zones were found in the Changle-Nan'ao zone. Single deformed zones have a wi dth from several meters to dozens meters. Asymmetric ductile shear criteria that can be used to distinguish a sense of shear include σ-type asymmetric porphyro clastic system, feldspar or quartz augen structure, fish-tails of mica, S-C comp osite foliation, dynamical recrystallized quartz aggregates in an oblique direct ion and fibrous chlorite pressure shadows around a large pyrite, and so on. Thi s paper proposes that this zone was a high temperature domain provided by shear heating, and ductile deformed fabrics were formed syntectonically during emp lace ment of granitic magma, which provided the heat for metamorphism. This is confirmed by occurrence of most high temperature minerals near granitoids, and the metamorphism and deformation in wall rocks away from granitic bodies becomes weaker gradually. Ductile deformation took place in t he interval of 100～120 Ma and at the depth of middle crust. Metamorphism, mylon itization and granitic magmatism resulted from a Late Mesozoic collision of Paci fic oceanic plate that subducted toward the continental margins of Eastern Asia along the Japan ese Central Tectonic Line to the longitudinal valley zone in Taiwan. Three phase s of granitic magmatism can be recognized in the zone: the subduction-type or CA-type gra nitoids with low-K2O content about 160～180 Ma, the strike-slip-type foliated and mylo nitized granitoids about 100～120 Ma, and the A-type or exte nsional type granite accompanied by magma mixing or basaltic magma underplating. |
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| Keywords: | granitoids metamorphism-deformation structural constraints Late Mesozoic Changle-Nan'ao fault zone |
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