摘要
阿尔金山地区巴什考供以北、阿尔金山北缘断裂以南为一套变质程度达角闪岩相的片岩、大理岩夹少量斜长角闪岩。地球化学研究表明 ,这些斜长角闪岩原岩为玄武质成分 ,具有拉班玄武岩的特点。斜长角闪岩全岩Sm -Nd同位素等时线年龄为 1185± 130 (2σ)Ma ,其INd=0 .5 114 0 ,εNd(t) =+5 .8± 0 .6 ,表明原岩形成于中元古代晚期 ,源自亏损地幔。斜长角闪岩中角闪石4 0 Ar - 39Ar同位素分析显示变质作用发生在 6 12± 5 .8Ma之前 ,进一步表明其原岩应该形成于前寒武纪。这些年龄的确定 。
A set of schist and marble rocks with a few layers of plagioclase amphibolites are distributed to the north of Bashikaogong, Altun Tagh mountains, and experienced amphibolite facies metamorphism. These plagioclase amphibolites exhibit the features of tholeiite in their major element compositions and REE patterns, indicating their basaltic parent rocks. Four samples of these plagioclase amphibolites were analyzed for Sm-Nd isotopes. An isochron with 1 185±130 Ma was obtained whth I_(Nd)=0.511 40 and ε_(Nd)(t) =+5.8±0.6, suggesting that these plagioclase amphibolites were formed at the later Mesoproterozoic and derived from the depleted mantle. Integrated with ^(40)Ar-^(39)Ar data of metamorphic hornblendes with the greatest metamorphic age of 612±5.8 Ma, it is further proved that these plagioclase amphibolites were formed during the Precambrian. These geochronological and isotopic new data give us some important information about the Late-Precambrian tectonic framework in the Altun Tagh Mountains.
出处
《高校地质学报》
CAS
CSCD
2004年第4期528-534,共7页
Geological Journal of China Universities
基金
国家自然科学重点基金 (4 0 0 32 0 10 )
青年基金 (4 980 2 0 2 3)
北京大学测试基金资助项目
