摘要
四方台杂岩体是北秦岭沿商-丹带出露的基性-超基性杂岩体中最大的一个,出露面积约40 km2,由超基性-基性-中性岩石组成,侵入到丹凤群中。对四方台杂岩体中辉长岩锆石进行LA-ICP-MS微区定年研究,获得岩体的成岩时代为460±29 Ma。获得的32个测点可明显地分为400－500 Ma、700－900 Ma、1 800－2 600 Ma和2 700－2 918 Ma这4个时段,可能分别代表了北秦岭造山带不同地质时期的构造-岩浆事件的时代信息。其中400－500Ma与北秦岭地区表现强烈的加里东运动时限一致,而700－900 Ma则可能与830－740 Ma中国中西部地区响应积极的、造成Rodinia超大陆裂解的地幔柱活动有关。
Sifangtai complex is the largest mafic-ultramafic intrusion along the Shangdan fault in the North Qinling orogenic belt,covering an area of ～40 km2.It consists mainly of ultramafites,pyroxenite and minor intermediate rocks,intruding into the Danfeng Group.A combined study of cathodoluminescence images（CL） and in situ LA-ICP-MS U-Pb isotope dating was carried out for zircons from the Sifangtai gabbro.Cathodoluminescence images show two kinds of zircon grains, i.e.,prismatic ones with clear magmatic zonations and round ones with complicated internal structure,some of the latter ones having no magmatic zonation.Altogether 32 U-Pb analyses were made for cores and overgrowths of 26 zircon grains,and the magmatic age 460±29 Ma of Sifangtai mafic-ultramafic complex was obtained.The 32 data can be divided into 4 phases： 400～500 Ma,700～900 Ma,1 800～2 600 Ma and 2 700～2 918 Ma.The result of 400～500 Ma is consistent with the Caledonian movement in the Qinling orogenic belt,while the result of 700～900 Ma is probably related to the mantle superplume that broke up Rodinia in middle and west China during 830～740 Ma.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2012年第4期524-530,共7页
Acta Petrologica et Mineralogica
基金
国家自然基金资助项目(30773044)
长安大学中央高校基金(CHD2010JC042)
中央级公益性科研院所基本业务费资助项目(K1019)
