扬子陆块庙湾蛇绿岩中橄榄岩的 同位素年代学及其构造意义
作者简介:
邱啸飞(1985-),男,博士,助理研究员,主要从事同位素地球化学和岩石地球化学研究
- 1. 中国地质调查局武汉地质调查中心,湖北武汉430205 2.中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205
- 收稿日期:
2015-08-28
- 修回日期:
2015-08-28
- 刊出日期:
2015-08-28
基金项目:
国家自然科学基金项目(No.41303026)中国地质调查局地质调查项目(Nos.12120114005701,1212011220512,1212011121102).
摘要: 扬子陆核崆岭高级变质地体内出露一套强变形的基性-超基性岩岩石组合,主要呈似层状、透镜状分布于崆岭群中,该
套变基性-超基性岩组合对扬子陆块早期构造演化过程具有重要意义.通过同位素稀释法(isotopedilutionthermalionization
massspectrometry,简称ID-TIMS)获得该套岩石组合中蛇纹石化方辉橄榄岩全岩Sm-Nd等时线年龄为1063±12Ma,说明
Sm-Nd同位素体系可用于对超低含量、发生强蚀变作用的超基性岩样品进行定年.样品Nd同位素组成相对均一(εNd(t)值为
6.90~7.32),表明形成于封闭体系中,其对应Nd同位素两阶段模式年龄为1.13~1.09Ga,与形成年龄接近,说明来自亏损软
流圈地幔部分熔融.结合区域上已有的中元古代末期到新元古代早期构造岩浆事件研究,认为在该时期扬子陆块可能由多个
微陆块组成,就扬子陆核而言,其与扬子陆块西侧之间很可能存在分隔的大洋.
Geochronology of Serpentinized Harzburgite in Miaowan 〇phiolite, Yangtze Block and Its Tectonic Implications
- 1. WuhanCenterofChinaGeologicalSurvey,Wuhan 430205,China 2.ResearchCenterofPetrogenesisand MineralizationofGranitoidRocks,ChinaGeologicalSurvey,Wuhan 430205,China
- Received Date:
2015-08-28
- Accepted Date:
2015-08-28
- Available Online:
2015-08-28
Fund Project:
国家自然科学基金项目(No.41303026)中国地质调查局地质调查项目(Nos.12120114005701,1212011220512,1212011121102).
Abstract: A series of strongly-deformed mafic-ultramafic rocks occur at the Kongling high-grade metamorphic terrain in Yan-
gtze continenta1 nucleus, scattering in the Miaowan Formation inlayers and podiforms. This metamafic-ultramafic rock associa-
tion is of great significance to the early tectonic evolution of Yantgze b1ock. In this study, ID-TIMS whole-rock Sm-Nd isochron
dating is carried out for the serpentinized harzburgite and amphibolite from this rock suite. The results indicate that the serpen-
tinized harzburgite was formed at1 063土12 Ma, showing that it is feasible to date tiny amount of heavily-altered ultramafic
rocks by means of the Sm-Nd isotopic system. The comparatively uniform Nd isotopic composition(with eNd(t) value ranging
from6.90 to7.32) indicates that they were formed in a c1osed system. Two-stage Nd moda1 age of 1.13-1.09 Ga is c1ose to
their emplacement time, implying an origin of partia1 melting from depleted asthenospheric mantle. Combined with documented
workonlate Mesoproterozoic to early Neoproterozoic tectonic-magmatic events in the area, it is suggested that the Yangtze
b1ock may have been composed of severa1 microcontinents at that time. There could have been an ocean separating the Yangtze
continenta1 nucleus from western Yangtze continenta1 segment.