摘要
浙江龙泉石英二长岩的Sm-Nd同位素等时线年龄为2059±52Ma,它代表了该岩体的结晶年龄,并且也是目前在浙、闽地区发现的最老的花岗质岩浆侵位年龄。由此表明,浙、闽地区最初的岩浆活动可能始于早元古代。Rb-Sr同位素等时线年龄仅反映该岩体受到后期地质作用扰动的年龄信息。该岩体属于一种S型或改造型花岗岩类,t_(DM)^(Nd)为2600—2700Ma,反映了本区最早的地壳形成年龄属于晚太古代。上述的早元古代花岗岩的发现和由此得到的晚太古代基底的年龄信息将对进一步研究中国东南大陆地壳的演化提供新的证据。
The Longquan adamellite body lies in the southern of Zhejiang Province,China. The adamellite body was dated by using Sm-Nd and Rb--Sr techniques. The Sm-Nd Internal isochron age obtained by dating 3 whole rock and 2 single--mineralsamples is 2059±52 Ma. The age value is considered as the emplacement age of theadamellite body in the Longquan area. Therefore, the age value indicates that theearliest activity of granitic--magma in Zhejiang and Fujian took place in the EarlyProterozoic rather than in the Middle Proterozoic or the Palaeozoic. The Rb--Sr ageof the adamellite body is 665.5±21.4 Ma. The Rb--Sr age reflects the age of thisintrusion after the disturbation of the subsequent geological processes. In combination with the geological evidence and geochemical data, it is believedthat the adamellite body belongs to a S--type or transformation-type granite. It wasformed by partial melting of the crustal materials mainly of sedimentary constitu-ents. i_(DM)^(Nd) of 5 whole rock--mineral samples is about 2 600--2 700Ma. These model agesare in agreement with the U--Pb age data that they published. Hence, these modelages indicate the age of the oldest basement in the southeast of China and the sourcematerials of the granite body derived from the depleted mantle source during thelate Archaean. The existence of the Upper Archaean crust in this area provides newinformation for the study of the formation and evolution of the Zhejiang-Fujiancontinent or the southeast continent of China.
出处
《地质论评》
CAS
CSCD
北大核心
1992年第6期525-531,共7页
Geological Review
基金
国家自然科学基金(编号949001101)
关键词
花岗岩
基底
时代
早元古代
adamellite
Sm--Nd dating
emplacement age and basement
