豫西太山庙铝质A型花岗岩SHRIMP锆石U-Pb年龄及其地球化学特征  

SHRIMP Zircon U-Pb Dating and Geochemistry of the Taishanmiao Aluminous A-type Granite in Western Henan Province

作　　者：叶会寿[1] 毛景文[1] 徐林刚[2] 高建京[2] 谢桂清[1] 李向前[2] 何春芬[3] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质大学,北京100083 [3]河南省地质矿产勘查开发局第一地质调查队,河南洛阳471023

出　　处：《地质论评》2008年第5期699-711,共13页Geological Review

基　　金：国家自然科学基金(编号40434011)的成果。

摘　　要：太山庙岩体位于华北陆块南缘豫西地区,呈岩基产出,出露面积约290km^2。根据它们的接触关系可以划分为3期:第1期中粗粒碱长花岗岩、第2期细中粒碱长花岗岩、第3期碱长花岗斑岩。利用SHRIMP锆石U- Pb法对主要岩性中粗粒碱长花岗岩进行测年的结果表明:其成岩年龄为115±2Ma,晚于区域上的南泥湖等花岗斑岩体和文峪、花山、合峪等花岗岩基。在矿物组成和化学成分特点上,这3期花岗岩基本相似,主要由条纹长石、钠长石(An<10)、石英和少量的黑云母组成,发育晶洞构造;具富硅(SiO_2 70.63%～76.59%),偏碱(Na_2O+K_2O 8.23%～9.34%),FeO~*/MgO值相对较高(3.00～7.21),CaO和MgO含量低(分别为0.46%～1.18%和0.15%～0.65%),准铝质—弱过铝质(A/CNK为0.95～1.13)的特点;微量元素特征上,明显富集REE(Eu除外)、Zr、Nb和Ta等高场强元素(HFSE),而Sc、Cr、Co、Ni、Sr和Eu等含量较低。此外,还具有较高的Ga/Al比值特征(2.7～3.6),所有这些特征均说明其与I型和S型花岗岩有明显的区别,而具有铝质A型花岗岩的特点,在相关判别图解上属于A1型花岗岩,表明其形成于板内拉张环境。The Taishanmaio intrusion is situated in the western Henan province as a batholith, which is on the southern margin of the North China craton with an area of ca. 290 km^2. Based on the contact relationship, it can he divided into three stages （from early to late）： medium-coarse grained alkalifeldspar granite, fine-medium grained alkali-feldspar granite and alkali-feldspar granite porphyry, respectively. The SHRIMP U-Pb zircon dating for the primary medium-coarse grained alkali-feldspar granite yields an age of 115±2Ma, which is later than Nannihu granite porphyries and Wenyu, Huashan, Heyu granite batholiths in this area. All three stages of granites have similar mineralogy and geochemistry. They are composed biotite, with miarolitic structures, -1. 13） and characterized by high 47.21） and low CaO（0.46% -1. of primary perthite, albite（An〈10）, quartz and a small quantity of and they are metaluminous and slightly peraluminous （A/CNK=0.95 silica（70.63%-76.59%）, alkali（8.23%-9.34%）, FeO^＊/MgO（3.00 18%） and MgO（0. 15%-0. 65%）. They also have relatively higherREE （except for Eu） and high strength field elements such as Zr, Nb and Ta concentrations, but lower Sc, Cr, Co, Ni, Sr and Eu concentrations. In addition, they have relatively high Ga/A1 ratios （2.7-3. 6）, characterizing A-type granite, neither I nor S types of granite. On the geochemical discrimination diagrams, they can be classified into A1 type, and formed during the lithospheric extensional movement.

关 键 词：SHRIMP年龄 地球化学特征 铝质A型花岗岩 太山庙岩体 豫西 

分 类 号：P597[天文地球—地球化学]