【摘要】 东昆仑南地体最古老的变质基底为苦海岩群,出露于苦海-温泉一带。采用LA-ICP-MS方法对苦海岩群副片麻岩中的锆石进行测试,得出苦海岩群副片麻岩的最大沉积时代为新元古代早期且在志留纪（423 Ma）遭受变质。通过与东昆仑北地体变质基底金水口岩群的锆石年龄谱对比,苦海岩群和金水口岩群的锆石年龄谱中都存在1 550¹ 650 Ma、1 900² 100 Ma、2 350² 550 Ma的年龄段峰值,两岩群可能存在相似的物源区;年龄谱中最年轻的岩浆锆石峰值年龄分别为750⁸00 Ma和900¹ 250 Ma,两岩群的最大沉积时代相近,分别为新元古代早期（Pt₃）、中元古代晚期-新元古代早期(Pt_2-3);年龄谱中都存在400⁴50 Ma的变质年龄峰值,两岩群在志留纪均发生角闪岩相变质,说明它们在前志留纪有着相似的演化历史。即使昆南地体和昆北地体之间在早古生代期间存在洋盆,该洋盆也不会太大。更多还原

【Abstract】 The Kuhai Group is the oldest metamorphosed basement in southern East Kunlun Terrane( SEKT)which is exposed around Kuhai-Wenquan area. This study presents in situ zircon U-Pb analyses( LA-ICP-MS) of67 zircons from two paragneisses in the Kuhai Group in SEKT. The results suggest that the Kuhai Group was deposited in Early Neoproterozoic and underwent a metamorphic event in Silurian( 423 Ma). Compared with the zircon U-Pb dating of the Jinshuikou Group in northern East Kunlun Terrane( NEKT),the ages of their source materials all have the records of 1 550 ~ 1 650 Ma,1 900 ~ 2 100 Ma and 2 350 ~ 2 550 Ma,suggesting that they might have had similar sources; peak ages of the youngest member in the age spectrum with magmatic origin are 750 ~ 800 Ma and 900 ~ 1 250 Ma respectively,suggesting that their earliest sedimentary ages are Early Neoproterozoic and Late Mesoproterozoic-Early Neoproterozoic respectively; peak ages of the youngest member in the age spectrum with metamorphism origin are 400 ~ 450 Ma,indicating that they all underwent the amphibolite facie metamorphism in Silurian. It can therefore be inferred that the oldest metamorphosed basements in SEKT and NEKT had the similar evolution histories during pre-Silurian,and even if the paleo-ocean basin between the SEKT and the NEKT existed in early Paleozoic,the ocean basin must have been a small one.更多还原