摘要
青藏高原南部谢通门地区出露一些中侏罗世的闪长岩,岩石具有类似于埃达克质岩的地球化学特征,如高的SiO2(>59%)、Sr(771～798μg/g)、低HREE和Y(<12μg/g)含量,高Sr/Y(>64)、La/Yb(4.4<(La/Yb)N<19.2)值,较高的MgO(3.02%～3.17%),具有一定Sr正异常和无明显Eu负异常。拉萨地块南部在中侏罗世时期不仅发育有基性和酸性的岩浆作用,而且还发育有斑岩型矿床——雄村斑岩Cu-Au矿床。另外,谢通门闪长岩具有与太平洋西北部Bowes Ridge地区中基性埃达克质岩十分相似的地球化学特征,而后者形成于中新世俯冲大洋板片断离的构造环境之中。因此研究区中侏罗世谢通门闪长岩很可能为北向俯冲的新特提斯洋板片断离并发生部分熔融的产物。
The Middle Jurassic diorite exposed in the Xietongmen area of Southern Tibet,have some adakitic characteristics,such as high SiO2( >59%) and Sr( 771 ～ 798 μg/g),and low HREE,and Y( <12 μg/g) concentrations,high Sr / Y( > 64) and La / Yb( 4. 4 <( La / Yb)N< 19. 2) ratios,with positive Sr anomalies but no obvious Eu anomalies. Middle Jurassic basic and acidic magmatism and related porphyry deposits( Xiongcun porphyry CuAu deposits) were recognized in Southern Tibet. In addition,the geochemical characteristics of the diorite are similar to those of the Cenozoic volcanic rocks at Bowers Ridge resulting from partial melting of slab-tearing in northwestern Pacific Ocean. So,we suggest that the diorite in the Xietongmen area was most likely derived from partial melting of the slab break-off during the northern-dipped Neotethys Ocean in Middle Jurassic.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2013年第2期320-332,共13页
Geotectonica et Metallogenia
基金
国家973项目(编号:2011CB403100,2009CB421004)
中国科学院战略性发展科技专项(B类)(XDB03010301)
中国地质调查局项目(编号:1212011121225,1212010818098)
国际合作项目(编号:IGCP/SIDA-600)
国家自然科学基金项目(批准号:40872055、40930316)联合资助
