江西吉泰盆地碱性玄武岩的地球化学特征及其构造意义

现代地质 ›› 2005, Vol. 19 ›› Issue (1): 133-140.

江西吉泰盆地碱性玄武岩的地球化学特征及其构造意义

余心起¹，舒良树^2,*，邓国辉³，王彬²，祖辅平²

1 中国地质大学地球科学与资源学院，北京100083；
2南京大学地球科学系，江苏南京210093；
3 江西地质调查院，江西南昌330201

收稿日期:2004-10-25 修回日期:2004-12-20 出版日期:2005-01-20 发布日期:2005-01-20
通讯作者: 舒良树
作者简介:余心起，男，高级工程师，博士后，1962年出生，构造地质学专业，主要从事构造地质学及沉积大地构造学的研究工作。
基金资助:
国家自然科学基金项目（40172067）；国家自然科学重点基金项目(40132010)

Geochemical Features and Tectonic Significance of the Alkali-Basalts from Ji’an-Taihe Basin,Jiangxi Province

YU Xin-qi¹，SHU Liang-shu^2，*，DENG Guo-hui³，WANG Bin²，ZU Fu-ping²

1School of Earth Sciences & Resources, China University of Geosciences, Beijing100083, China;
2Department of Earth Sciences, Nanjing University, Nanjing，Jiangsu210093, China;
3Academy of Geological Survey of Jiangxi Province, Nanchang，Jiangxi330201, China

Received:2004-10-25 Revised:2004-12-20 Online:2005-01-20 Published:2005-01-20

摘要/Abstract

摘要：

吉泰盆地位于赣中地区，目前尚无在该盆地中发现玄武岩的报道。新发现的玄武岩产于吉泰盆地南部泰和附近的南溪镇。玄武岩露头新鲜，蚀变微弱，属碱性玄武岩，形成于板内快速拉张环境；锆石U-Pb年龄为(139±0.7)～(143±1.1)Ma，表明岩石形成于早白垩世早期。玄武岩无明显的Nb、Ta负异常，Rb-Sr、Sm-Nd同位素组成分析结果显示[N(⁸⁷Sr)/N(⁸⁶Sr)]_i=0.704 1～0.704 8, ε_Nd(t)= +3.78～+4.38，反映玄武岩浆起源于亏损地幔，未经地壳物质混染。结合吉泰盆地边部存在中侏罗世(168 Ma)玄武岩的事实，表明赣中地区在早白垩世已经处于拉张背景，吉泰盆地的碱性玄武岩可能是在板内岩石圈伸展减薄作用下，由北东向的赣江断裂带拉张形成的。

关键词: 碱性玄武岩, 亏损地幔, 板内拉张环境, 早白垩世早期, 赣江断裂, 吴川—四会断裂, 吉泰盆地

Abstract:

New found basalt crop is located near the Nanxi Town, Taihe County, south of Ji'an-Taihe Basin, middle Jiangxi Province. With brown-grey and dark green color, the fresh basalt has compacted texture and some blisters and amygdules. Microscope observation reveals that the rocks have intergranular textures,more than 60% basic plagioclases, filling with olivines and augites, less than 5% almond-shaped calcites, and weak corrosion. According to its geochemical features, the basalt belongs to alkalibasalt, produced by quick regional extension within a plate. Rb-Sr and Sm-Nd isotopic composition of the basalt are as follow:(⁸⁷Sr/⁸⁶Sr)_i =0.704 1-0.704 8 and ε_Nd(t)=+3.78-+4.38, indicating that the magma came from the deficit mantle and had not mixed with crust material. The zircon solution U-Pb geochronological data of(139±0.7)to(143±1.1)Ma for the alkali-basalt indicates that mantle-reached strike-slip faulting along northeast-striking Ganjiang Fault and Wuchuan-Sihui Fault was active from early period of Early Cretaceous under the extensional background of the area

Key words: alkali-basalt, deficit mantle, extension environment within a plate, early period of Early Cretaceous, Ganjiang Fault, Wuchuan-Sihui Fault, Ji'an-Taihe Basin

中图分类号:

P588.14⁺5

余心起，舒良树，邓国辉，王彬，祖辅平. 江西吉泰盆地碱性玄武岩的地球化学特征及其构造意义[J]. 现代地质, 2005, 19(1): 133-140.

YU Xin-qi，SHU Liang-shu，DENG Guo-hui，WANG Bin，ZU Fu-ping. Geochemical Features and Tectonic Significance of the Alkali-Basalts from Ji’an-Taihe Basin,Jiangxi Province[J]. Geoscience, 2005, 19(1): 133-140.

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