新疆准噶尔北东缘乌图布拉克岩体形成时代、地球化学特征及地质意义  

Formation time and geochemical feature of Wutubulak pluton in the northeastern margin of Junggar in Xinjiang and its geological significance

作　　者：周刚[1,2] 吴淦国[1] 董连慧[1,3] 张招崇[1] 董永观[4] 童英[5] 何立新[2] 应立娟[6] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]新疆维吾尔自治区地质矿产勘查开发局第四地质大队,阿勒泰836500 [3]新疆维吾尔自治区地质矿产勘查开发局,乌鲁木齐830000 [4]南京地质矿产研究所,南京210016 [5]中国地质科学院地质研究所,北京100037 [6]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石学报》2009年第6期1390-1402,共13页Acta Petrologica Sinica

基　　金：国家305项目(2007BAB25B01);国家自然科学基金项目(40702010)资助.

摘　　要：乌图布拉克岩体位于准噶尔北东缘,额尔齐斯-玛因鄂博构造带南侧。岩体主要由花岗闪长岩和二长花岗岩组成,有少量石英闪长岩和钾长花岗岩。岩体的锆石SHRIMP U-Pb年龄为360.1±3.6Ma。岩石的K_2O+Na_2O=7.05%～9.48%, A/NKC=0.91～1.04,属准铝-过铝质"Ⅰ"型花岗岩。岩石稀土总量低,∑REE为72×10^(-6)～184×10^(-6),轻稀土富集,(La/Yb)_N=5～13。石英闪长岩、花岗闪长岩、二长花岗岩具弱的铕负异常或无明显异常(δEu=0.72～0.98);钾长花岗岩铕负异常明显(δEu=0.15～0.21)。在微量元素配分模式中,具有Sr、Ba、P、Ti的亏损,而Nb、Ta亏损不明显。岩石有低的Sr初始值(0.70165～0.70462)和高的ε_(Nd)(t)(+4.7～+6.9)。2个样品的Nd模式年龄分别为758Ma和551Ma。上述特征表明,岩浆可能具有较复杂的来源,推测该岩体岩浆可能来源于年轻的玄武质地壳,并有幔源物质的加入。综合本文资料及区域地质特征分析,阿尔泰造山带后碰撞时限可能为360～290Ma,即泥盆纪末-石炭纪末。The Wutubulak pluton is located in the northeastern margin of Junggar and the southern side of the Ertrix-Mayin'ebo tectonic belt. This pluton is composed of granodiorite and monzogranite, and a few of quartz diorite and moyite. Zircon SHRIMP U-Pb age of this pluton is 360.1 +/- 3. 6Ma. It's K2O + Na2O content reaches 7.05% similar to 9.48%. The A/NKC value (0.91 similar to 1.04) indicates it belongs to the metaluminous and prealuminous as 'I' type granite. REE content is quite low, so that its Sigma REE changes only between 72 x 10(-6) and 184 x 10(-6) with a richenment of light REE as (La/Yb) x value between 5 and 13. There is a slight negative Eu anomaly or no obvious Eu anomaly of quartz diorite, granodiorite and monzogranite (delta Eu 0.72 similar to 0.98), whereas moyite contains an obvious negative Eu anomaly (delta Eu 0.15 similar to 0.21). Incompatible elements such as Rb, Th, K are richened, Sr, Ba, P and Ti are poor and the deficiency of Nb and Ta is not obvious. Initial Sr value changes between 0.70165 and 0.70462, and its epsilon(Nd) 0 is positive as + 4.7 similar to 6.9. Mode ages of two samples are 758Ma and 551Ma. These suggest the magmatic sources are complex, may from new basaltic crust, and with the additional mixture of young mantle-source material. Based on the previous research work, time limit of post-collision of Altay orogen might be between 360Ma and 290Ma, namely between the end of Devonian and the end of Carboniferous.

关 键 词：乌图布拉克岩体 锆石SHRIMPU-PB年龄 地球化学 后碰撞时限 准噶尔北东缘 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]