中国东南部晚中生代岩浆作用的深部条件制约  

Deep Geological Conditions Constraning the Late Mesozoic Magmatism in SE China

作　　者：徐鸣洁[1] 舒良树[1] 

机构地区：[1]南京大学地球科学系,江苏南京210093

出　　处：《高校地质学报》2001年第1期21-33,共13页Geological Journal of China Universities

基　　金：国家自然科学基金!重点资助项目 (批准号 :496 32 0 80 )

摘　　要：通过对中国东南部区域地质条件的分析和地球物理资料的研究 ,获得了如下认识 :1.区域构造作用和基底物质成分影响并制约着晚中生代岩浆活动 ,岩浆岩的分区性具有很好的地表与深部一致性 ;2 .按岩浆岩类型可分三区 ,即沿海钙碱性中酸性火山 -侵入杂岩区、武夷山弱过铝花岗质火山 -侵入杂岩区和赣江以西强过铝花岗岩区 ,三者之间分别被政和—大埔断裂与赣江断裂所分隔 ;3.在沿海地区 ,存在局部高导层 ,推测与拉开裂解有关。玄武岩浆底侵和碱性花岗岩形成与晚白垩世拉张作用关系密切 ;4 .政和—大埔、赣江和长乐—南澳三大断裂是重力梯度带或梯度突变带 ,且深部地球物理场存在明显差异 ,可能是壳幔作用剧烈的场所 ;5.存在中地壳低速带 ,厚2～ 4km ,为地壳部分熔融或韧性变形产物 ,推测是部分晚中生代花岗岩浆的策源地 ;6.支持中国东南部晚中生代岩浆作用的板块俯冲 +陆内玄武岩浆底侵的成因模式 ,日本中央构造线—台湾纵谷带是中生代太平洋板块朝东亚陆缘消减的俯冲带和缝合带。Analyses of regional geologic settings and geophysic data have yielded following results: 1.The regional tectonism and material composition of basement had influenceon the Late Mesozoic magma activity, and the magmatic division at the surface is consistent with that in the deep. 2. Based on the types of magmatic rocks, three tectonic magma regions are recognized: (a) low K and high Al calc alkaline intermediate acid volcanic intrusive complex region, i.e., SE China Coastal Region; (b) high K granitic volcanic intrusive complex region, named as the Wuyishan region and (c) high K S type granite region in the west to Ganjiang without acid volcanic intrusive complex. These three regions are separated by Zhenghe Dapu and Ganjiang fault zones respectively. The crustal thickness in the SE China Coastal Region is thinner, whose basement is mostly volcanic and granite belongs to I type; the crustal thicknesses for other two regions are greater than the first, their basements are mostly melted sedimentary rock series and the granitic rock is S type. The Ganjiang fault zone is called as the Late Mesozoic Volcanic Rock Line. 3.In the SE China Coastal Region, there is a local low resistivity layer, which was related to a pull rifting. The undeerplating of basaltic magma and the formation of alkaline granit were closely related to the pull rifting in the Late Cretaceous. 4. Zhenghe Dapu, Ganjiang and Changle Nan'ao fault zone have apparent geophysic features, which are both the gravity gradient zones and ultra crust fault zones where the geological interaction along the crust mantle boundary is most common. 5.There is a low velocity zone of 2 4km thick in the middle crust, and is considered as a result of a part melting of ductile deformation, which is probably a local magmatic source. 6. Our study supports the model of plate subduction combining with underplating of basalt magma for the origin of the Late Mesozoic magmatism in the SE China. The fault zone from the Japanese Central Tectonic Line t

关 键 词：岩浆作用 地球物理 晚中生代 中南 火成岩 基底构造 重磁异常 深部结构 

分 类 号：P588.1[天文地球—岩石学]