| 赣杭构造带龙游地区早白垩世基性岩矿物化学、岩石地球化学特征及其地质意义 |
| |
| 引用本文： | 卢宽,杜诗琰,张若曦,邹妍,蔡逸涛,杨水源.赣杭构造带龙游地区早白垩世基性岩矿物化学、岩石地球化学特征及其地质意义[J].地质通报,2019,38(1):163-176. |
| |
| 作者姓名： | 卢宽 杜诗琰 张若曦 邹妍 蔡逸涛 杨水源 |
| |
| 作者单位： | 中国地质大学(武汉)地质过程与矿产资源国家重点实验室, 湖北 武汉 430074,中国地质大学(武汉)地质过程与矿产资源国家重点实验室, 湖北 武汉 430074,中国地质大学(武汉)地质过程与矿产资源国家重点实验室, 湖北 武汉 430074,浙江第七地质大队, 浙江 丽水 323000,中国地质调查局南京地质调查中心, 江苏 南京 210016,中国地质大学(武汉)地质过程与矿产资源国家重点实验室, 湖北 武汉 430074 |
| |
| 基金项目： | 国家重点研发计划项目《热液型铀矿示范区岩浆演化及晚期酸性岩（脉）地质年代学研究》（编号：2017YFC0602601）和国家自然科学基金项目《赣杭构造带大洲铀矿田REE矿化机制及其与U成矿耦合关系研究》（批准号：41773040） |
| |
| 摘 要： | 通过龙游晚中生代基性岩岩相学观察、全岩主量、微量元素和Sr-Nd同位素及矿物电子探针分析,对岩石成因、岩浆演化和构造环境进行探讨。龙游基性岩岩性为橄榄辉长岩,Sr-Nd同位素显示为幔源特征;主量、微量元素特征显示其经历了以橄榄石、辉石为主的分离结晶作用,且未发生明显的地壳物质混染。橄榄石颗粒具核-边结构,富Mg贫Fe的核部Fo值为90.1～91.8,指示原始岩浆是软流圈地幔,富Fe贫Mg的边部显示橄榄石Fo值为77.4～85.3,且核-边两部分的Fo值相差较大,显示原始橄榄石形成之后受到地幔熔体/流体的交代作用。辉石斑晶大多属于透辉石,在部分斑晶的边部发育少量霓辉石。透辉石斑晶普遍具有核-幔-边结构,从核部到边部的SiO_2含量降低,TiO_2、Al_2O_3含量升高,结晶温度升高,显示原始辉石形成之后受到温度更高的地幔熔体/流体的交代作用。研究认为,古太平洋板块后撤造成岩石圈地幔拉伸作用并形成赣杭构造带深部断裂后,部分软流圈物质受到地幔流体/熔体的交代作用,并沿这些深部断裂向上侵位,经历了以橄榄石和辉石矿物为主的分离结晶作用和微弱的地壳物质混染,最终形成龙游橄榄辉长岩。
|
| 关 键 词： | 龙游 橄榄辉长岩 矿物学 地球化学 金刚石 |
| 收稿时间： | 2018/7/10 0:00:00 |
| 修稿时间： | 2018/9/12 0:00:00 |
Mineral chemistry, geochemistry and geological significance of Early Cretaceous mafic rock in Longyou area, Gan-Hang belt |
| |
| LU Kuan,DU Shiyan,ZHANG Ruoxi,ZOU Yan,CAI Yitao and YANG Shuiyuan.Mineral chemistry, geochemistry and geological significance of Early Cretaceous mafic rock in Longyou area, Gan-Hang belt[J].Geologcal Bulletin OF China,2019,38(1):163-176. |
| |
| Authors: | LU Kuan DU Shiyan ZHANG Ruoxi ZOU Yan CAI Yitao and YANG Shuiyuan |
| |
| Institution: | State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, Hubei, China,State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, Hubei, China,State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, Hubei, China,No.7 Geological Party, Geological Exploration Bureau of Zhejiang Province, Lishui 323000, Zhejiang, China,Nanjing Center, China Geological Survey, Nanjing 210016, Jiangsu, China and State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, Hubei, China |
| |
| Abstract: | There have been reports of diamonds found in the mafic rocks of Longyou, Zhejiang Province. However, the tectonic setting and host rock characteristics still lack detailed studies. In this paper, the authors carried out a detailed study of petrology, major and trace elements, Sr-Nd isotopic compositions and mineral chemistry for the Longyou mafic rocks in an attempt to unravel the petrogenesis, magma evolution and tectonic setting during Late Mesozoic period. Longyou mafic rocks can be classified as olivine gabbro. Isotope characteristics indicate that the olivine gabbro was derived from a deep mantle source. The major and trace elements show that they mainly underwent fractional crystallization of olivine and pyroxene, without any obvious crustal contamination. Olivine grains show a core-rim structure with the core being Mg-rich and Fe-depleted and Fo values being 90.1~91.8, which indicates that the original magma was an asthenospheric mantle. In contrast, the rim of the olivine grains is Fe-rich and Mg-depleted with Fo values being 77.4~85.3. The remarked difference in Fo values for the core and rim may indicate that the original olivine was replaced by mantle melt/fluid. Most pyroxene xenocrystals belong to diopside, and a small amount of aegirite augite is developed at the edge of some diopside xenocrystals. The diopside xenocrystal generally has a core-mantle-rim structure, exhibiting a decrease in SiO2 and increase in TiO2, Al2O3 and temperature of magmatic emplacement from the core to rim. The authors hold that this corerim trend may indicate that the pyroxenes were metasomatized by later higher temperature mantle melt/fluid. It is argued that the Longyou olivine gabbro was formed during the roll-back of the Paleo-Pacific plate along the deep faults of the Gan-Hang tectonic belt. The asthenospheric mantle melts moved upwards along these deep faults and the magma responsible for the Longyou olivine gabbro experienced the fractional crystallization between olivine and pyroxene with very low degree of or without crustal contamination. Furthermore, it is also suggested that the Longyou olivine gabbro experienced a metasomatism of higher temperature mantle melt/fluids. |
| |
| Keywords: | Longyou olivine gabbro mineralogy geochemistry diamond |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地质通报》浏览原始摘要信息 |
| 点击此处可从《地质通报》下载免费的PDF全文 |
|
