新疆温泉县哈布特乌兰一带青白口纪花岗岩地球化学特征、锆石U-Pb年龄及其构造意义

Geochemical characteristics,Zircon U-Pb ages and tectonic meaning of Qingbaikouan granites in Habutewulan area,Wenquan county,Xinjiang

新疆温泉县城以南哈布特乌兰一带,花岗岩较发育,共划分出2个侵入序次,由6个岩体组成。在该区第一侵入次获得LA-ICP-MS锆石U-Pb加权平均年龄值为882.8±8.5Ma,时代为青白口纪。该期花岗岩中K_(2)O、Na_(2)O含量偏高,K_(2)O/Na_(2)O较低,Al_(2)O_(3)>CaO+Na_(2)O+K_(2)O,A/NKC大于1.1,为S型花岗岩,属高硅、高钾钙碱性过铝质岩石。稀土元素总量为(19.14~70.3)×10^(-6),微量元素中RbN/YbN>1,δEu为0.1~0.35,小于0.7,有明显亏损。综合分析,本期侵入岩为交代成因的壳源型花岗岩,表明岩浆源于壳源的产物,随着岩浆温度、压力的不同逐渐分异结晶冷凝而成。

In Habutewulan area,south of Wenquan county,Xinjiang,granites are well developed and divided into two intrusive sequences consisting of six intrusions.LA-ICP-MS zircon U-Pb weighted average age of the first intrusive magma in this area is 882.8±8.5Ma,this age is in Qingbaikouan Period.The contents of K_(2)O and Na_(2)O in granites of this age are high,and the ratio of K_(2)O/Na_(2)O is low.Al_(2)O_(3)>CaO+Na_(2)O+K_(2)O,A/NKC value is greater than 1.1.It is S-type granite,belonging to calc-alkaline peraluminous rock with high silicon and high potassium.The total amount of rare earth elements is(19.14~70.3)×10^(-6),RbN/YbN is greater than 1,δEu value is 0.1-0.35,less than 0.7,showing obvious deficit.Comprehensive analysis shows that the intrusive rocks of this period are crust source granites of metasomatic cause,indicating that the magma is derived from crust source rocks and gradually crystallized and condensed with the difference of magma temperature and pressure.