当前位置:科学网首页 > 基金首页 > 高级变质作用中Zr的地球化学及锆石U—Pb年代学意义

国家自然科学基金项目查询

高级变质作用中Zr的地球化学及锆石U—Pb年代学意义

批准号40173014 学科分类金属常温腐蚀与防护 ( E011101 )
项目负责人王佳 负责人职称 依托单位中国科学技术大学
资助金额0.00
万元
项目类别面上项目 研究期限2002 年 01 月 01 日 至
2004 年 12 月 01 日
中文主题词大别-苏鲁造山带;超高压变质岩;Zr的地球化学;锆石微量元素;锆石U-Pb定年;
英文主题词Dabie-Sulu orogen; Ultrahigh pressure metamorphic rocks; Zr geochemistry; Zircon trace elements; Zircon U-Pb dating

摘要

中文摘要 通过对大别山各种超高压变质岩、麻粒岩的前进和退变质作用各阶段主要构成矿物Zr含量的分析,查清各阶段主要含Zr矿物种类及Zr含量的变化,示综不同变质反应过程中Zr的地球化学行为,为锆石变质增生提供Zr的来源的可能性。结合锆石结构及年代学研究,从而探讨不同岩石变质锆石增生和重结晶发生的主要阶段,为锆石变质年龄的地质解释提供理论依据。
英文摘要 This work concentrated on Zr geochemistry of gabbro(the protolith of eclogite) minerals, high-pressure and retrograde minerals in eclogites in the Dabie orogen. We observed that the clinopyroxene(CPX) in protolith gabbro is the major Zr-bearing mineral and the titanite has high Zr contents also. The Rutile is the high Zr-bearing mineral in eclogite, the garnet, omphacite and retrograde mineral(amphibole) have little Zr contents. Therefore, the Zr for high-pressure metamosphic overgroth of zircon was mainly contributed by decomposition of the CPX in gabbro during prograde metamorphism, so that the Zircon SHRIMP U-Pb ages will be older than the peak metamorphic age. During retrograde metamorphism with amphibolite facies, a little Zr released from rutile, which was transformed into titanite, can be supplied to zircon overgrowth. Therefore, SHRIMP U-Pb ages of retrograde overgrowth zircon should represent retrograde amphibolite facies age. Combined the trace elements of zircns with their CL images, we found the (Yb/Dy)N-Zr/Hf and (Yb/Dy)N-Th/U diagrams to differentiate the various metamorphic zircons. Based on zircon SHRIMP U-Pb, Sm-Nd and Ar-Ar isotopic datings and trace elements data of zircon and whole rock of the mafic granulite from Huilanshan in Lotian doming, we concluded that the protolith of the mafic granulite shoud be the Neoproterozoic mafic rocks, the granulite facies metamorphism of this rock was occurred at 124.0±1.8Ma and was cooling down to about 500℃ at 119.7±0.5Ma, which suggests a rapid cooling and uplifting of the Dabie Mountains in the early Cretaceous. The time coupling between the rapid uplifting of the mountains and voluminous magma intrusions or volcanics in the same area suggests a delamination and mountain root removing underneath the Dabie orgen in the Early Cretaceous. A precise age of 227.4±3.5Ma for peak metamorphism of eclogite from Qinglongshan has been obtained by combined studies of SHRIMP U-Pb dating, trace elements and mineral inclusions.
结题摘要 通过大别山超高压变质岩的原岩(辉长岩)矿物、榴辉岩中高压矿物和退变质矿物的Zr的地球化学研究,发现辉长岩中辉石是主要富Zr矿物相,副矿物榍石具有较高的Zr含量。榴辉岩中金红石是富Zr矿物,而石榴子石,绿辉石及退变质角闪石均含Zr很低。因此高压变质增生锆石的Zr主要来源于高压前进变质阶段辉石的分解反应,其相应锆石年龄应略老于压力峰期变质时代。在退变质过程中,金红石退变为榍石的反应可释放少量Zr,因此退变质增生锆石U-Pb年龄应指示角闪岩相退变质时代。根据锆石的痕量元素特征,提出区别各类不同成因变质锆石的(Yb/Dy)N-Zr/Hf及(Yb/Dy)N-Th/U微量元素判别图解。罗田穹隆惠兰山基性麻粒岩的锆石U-Pb、Sm-Nd和Ar-Ar定年及锆石和全岩微量元素地球化学工作证明该麻粒岩的原岩形成于晚元古代,其麻粒岩相变质作用发生在124.0±1.8Ma,它冷却到500℃的年龄为119.7±0.5Ma。这证明大别山在早白垩世经历了一次快速抬升,它反映了深部的一次岩石圈拆离和去根过程。将锆石SHRIMP定年与痕量元素及包体矿物研究结合,精确测定了青龙山榴辉岩峰期变质年龄是227.4±3.5Ma

成果

序号 标题 类型 作者
1 Sm-Nd and zircon SHRIMP U-Pb dating of Huilanshan mafic granulite in the Dabie Mountains and its zircon trace element geochemistry 期刊 HOU Zhenhui|LI Shuguang|CHEN Nengsong|LI Qiuli|LIU Xiaoming|
2 超高压变质岩的放射性同位素体系及年代学方法 期刊 李曙光|侯振辉|李秋立|等.|
3 A combined study of SHRIMP U-Pb dating, trace element and mineral inclusions on high-pressure metamorphic overgrowth zircon in eclogite from Qinglongshan in the Sulu terrane 期刊 LI Qiuli|LI Shuguang|HOU Zhenhui|HONG Ji’an|YANG Wei|
4 大别造山带惠兰山基性麻粒岩的Sm-Nd和锆石SHRIMP U-Pb同位素年代学及锆石微量元素地球化学 期刊 侯振辉|李曙光|陈能松|李秋立|柳小明|
5 大别山超高压变质岩的冷却史及折返机制 期刊 李曙光|李秋立|侯振辉|等.|

关于我们| 网站声明| 服务条款| 联系方式| RSS| 中国科学报社 京ICP备14006957 京公网安备110402500057号
Copyright @ 2007- 中国科学报社 All Rights Reserved
地址:北京市海淀区中关村南一条乙三号   电话:010-62580783