摘要
笔者在甜水海地块中部麻扎地区新发现了晚寒武世花岗岩,并命名为苦鲁勒岩体。LA-ICP-MS锆石U-Pb定年表明其形成年龄为500.7±1.1~498.7±1.4Ma,属晚寒武世岩浆活动的产物。该花岗岩中无角闪石和白云母,具有高SiO_2(73.49%~77.47%)、中高K_2O(1.88%~4.14%)、低P_2O_5(0.02%~0.05%)的特征,铝饱和指数(A/CNK)为0.98~1.12;稀土总量偏高(∑REE=66.81×10^(-6)~135.43×10^(-6)),轻重稀土的分馏程度中等[(La/Yb)_N介于3.86~7.98之间,(La/Sm)_N介于3.46~4.22之间)],Eu具有明显负异常(δEu=0.35~0.66);微量元素以富集Rb、Th、U、K,亏损Nb、Ta、P、Ti、Sr为特征,属于准铝质到弱过铝质高分异I型花岗岩类。岩体中发育的辉绿岩、闪长岩暗色包体以及结合成岩过程判别图解,表明在苦鲁勒岩体的形成过程中可能有幔源物质的加入,很可能是岩浆经历了显著的基性岩浆混合事件后的结果。结合区域研究成果,认为苦鲁勒岩体很可能形成于原特提斯洋向南俯冲消减机制下的岩浆弧构造环境,推测在早古生代原特提斯洋存在双向俯冲。
We report a discovery of Kulule granites in the middle Tianshuihai Massif.Zircons separated from this granite is dated to be 500.7±1.1-498.7±1.4Ma by LA-ICP-MS.The granites are lack of amphibole and muscovite,with geochemical features of high SiO2（73.49% -77.47%）,middle-high K2O（1.88% -4.14%）and low P2O5（0.02% -0.05%）,which are similar to the typical metaluminous to weakly peraluminous I-type granites with high differentiation.Additionally,the granites have high total REE concentrations（66.81×10^-6-135.43×10^-6）,high（La/Yb）Nvalues（3.86-7.98）and（La/Sm）Nvalues（3.46-4.22）,strongly negative Eu anomalies（δEu=0.35-0.66）,which display the enrichments of Rb,Th,U and K and the depletions of Nb,Ta,P,Ti and Sr.Microgranular mafic enclaves（MMEs）are common in the plutions and combined with the discrimination diagrams of diagenetic process,which implies the formation of Kulule granites has a mantle source and significant magma mixing.Based on the regional research,Kulule granites might be formed in an magmatic arc tectonic environment during the Proto Tethys southward subduction,which suggestsa bidirectional subductionof the Proto Tethys Ocean in the Early Paleozoic era.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第10期2582-2602,共21页
Acta Geologica Sinica
基金
中国地质调查局大地调项目"新疆1:5万J43E022019等5幅区调"(编号1212011120538)和"秦-祁-昆重要结合带组成
成因及演化研究"(No.:1212011121258)项目联合资助的成果
