摘要
位于腾冲地区的滇滩无极山铁矿区与成矿有关的岩浆岩为二长花岗岩,对二长花岗岩中锆石LA-ICP-MS U-Pb加权平均年龄测试结果为131.2Ma±2.8Ma,表明其形成于早白垩系。w(SiO2)范围为75.84%～78.07%,w(K2O+Na2O)为7.75%～8.64%,w(K2O/Na2O)>1,属高钾钙碱性花岗岩。在ACF(铝钙铁)图中,数据点都位于斜长石—白云母—堇青石区域内,与S型或壳源型花岗岩的范围十分一致。A/NK值为1.06～1.28(平均1.14),A/CNK值为0.92～0.97(平均0.94),属过碱准铝质花岗岩。在微量元素蛛网图上Rb,Ba,Ga,Nb,Ta,Th,U正异常明显,Sr,V,Cr,Co,Ni,Sc负异常明显,分布曲线明显呈现左侧"隆起"和右侧"下凹"的特征,相似于南岭地区的S型花岗岩。稀土配分曲线平缓,轻重稀土没有明显的分异特征,负Eu异常明显(δEu=0.04～0.05)。综合特征表明,滇滩无极山二长花岗岩为早白垩系壳源S型花岗岩。
Monzonitic granite is related to the mineralization of Wujishan iron deposit in the Diantan of Tengchong County. Zircon LA-ICP-MS U-Pb dating shows that monzonitic granite has an average weighted age of 131.2 Ma±2.8 Ma,belonging to early cretaceous, ω（SiO2） content ranges from 75.84%to 78.07%,ω（K2O＋Na2O） total content is 7.75%-8.64%,ω（K2O/ Na2O〉1,demonstrating that they are high K calc alkaline granites. In the ACF diagrams,data are plotted in the range of plagioclase-muscovite-cordierite,in accordance with range of S type or crust-derived type granite. A/NK value is 1.06-1.28 （average 1.14） and A/CNK value is 0.92 -0.97 （average 0. 94）,belonging to category of quasi aluminum quality granite. In the trace ele- ment spider diagram, Rb,Ba, Ga, Nb, Ta, Th, U are of obvious positive anomaly, while Sr, V, Cr, Co,Ni,Sc are of obvious negative anomaly,and the distribution curve is characteristic of left ＂up- lift＂ and right ＂sink＂, similar to S type or crust-derived type granite in the Nanling region. The smooth REE pattern,the poor fraction-ation between HREE and HREE,and strong depletion of EU （δEu = 0.04-0.05） indicate that Wujishan monzonitic granite belongs to crust-derived S type granite formed in the early Cretaceous.
出处
《矿物岩石》
CAS
CSCD
北大核心
2013年第1期53-59,共7页
Mineralogy and Petrology
基金
中国地质调查局地质矿产调查评价项目(1212011120608)(1212010781005)
