摘要
秦岭前寒武纪地质、地球化学和年代学证据表明 ,北秦岭具有明显高的初始εNd(t)值和Pb同位素比值特征 ,区别于明显低初始εNd(t)值和Pb同位素比值特征的华北陆块和扬子块体群。北秦岭与南秦岭具有明显不同的前寒武纪构造与演化特征。北秦岭是 2 0 0 0Ma左右形成于华北陆块南侧洋岛基础上的独立陆块 ,经历 2 2 0 0～ 180 0Ma和 140 0～ 90 0Ma分别以垂向加积增生和侧向加积增生为主要机制的地壳生长。北秦岭在早元古代洋盆演化基础上 ,首次于 16 0 0Ma左右拼接于华北陆块南缘 ,130 0～ 10 0 0Ma发生扩张裂解 ,出现宽坪裂谷 洋盆构造环境 ,10 0Ma左右再次拼贴于华北陆块南缘。同时 ,北秦岭南侧可能发生与南秦岭陆块群中的陡岭微陆块的拼接。
Evidence from Precambrian geology, geochemistry and isotopic ages suggests that North Qinling Terrane (NQT) is quite different from North China Block (NCB). The NQT is characterized by distinct higher initial ε Nd (t) values and Pb isotopic ratios, in contrast to the lower initial ε Nd (t)values and Pb isotopic ratios of the NCB. Geological evidence indicates that NQT is also different from South China Block (SCB), especially in Precambrian tectonic and evolution history. Based on synthesized studies of geology and geochemistry, it is suggested that NQT is an independent terrane, whose foundation is an oceanic island formed to the south of the NCB at about 2 000 Ma. The mechanism of two main crust growth events of NQT is vertical accretion and lateral accretion which occurred in 2 200～1 800 Ma and 1 400～900 Ma, respectively. Much evidence indicates that NQT was drifted in an early Proterozoic ocean and connected with the southern margin of NCB at about 1 600 Ma, and then drifted away from NCB due to the overspreading and formation of Kuanping rift-oceanic basin in about 1 300～1 000 Ma. At about 1 000 Ma, the NQT collided with the NCB along the northern boundary fault of Kuanping Group.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2003年第1期3-10,共8页
Acta Geoscientica Sinica
基金
国家自然科学基金项目 (编号 :40 0 0 30 0 3)
教育部骨干教师资助计划项目资助。
