皖南燕山期高钾钙碱性埃达克岩厘定及岩石成因  

Geochemical Characteristics and Petrogenesis of High-K Calc-alkaline Adakite of the Yanshanian Epoch in South Anhui

作　　者：翁望飞[1] 曹诚[1] 支利赓[1] 蔡连友[1] 徐生发[1] 王邦民[1] 

机构地区：[1]安徽省地质矿产勘查局332队地调院,安徽黄山245000

出　　处：《地质与勘探》2011年第6期967-981,共15页Geology and Exploration

基　　金：安徽省国土资源厅公益性地质调查基金项目<闪里幅(H50E013014)1:5万区域地质矿产调查>(项目编号:2010-g-11)资助

摘　　要：皖南及邻区晚侏罗世-早白垩世早期中酸性岩浆岩产于扬子陆块江南古隆起东段,主要岩石类型为花岗闪长岩,主矿物组合为斜长石+石英+钾长石+角闪石±黑云母,副矿物有磷灰石、锆石、榍石、磁铁矿、钛铁矿等。岩石主量元素具有高SiO2(66.81%)、Al2O3(15.23%)、K2O/Na2O(1.01),低TiO2(0.49%)、MgO(1.49%)、CaO(3.18%)、P2O5(0.18%)等特征;A/CNK值为1.04,呈弱过铝态,里特曼指数σ平均2.07,指示其属钙碱性系列。稀土元素表现为LREE富集,HREE亏损,具低Y(13.99×10-6)和Yb(1.4×10-6);微量元素表现为富集LILE(Rb、La、Ba、Sr)和亏损HFSE(Nb、Ta、Zr、Y),具高Sr(494.8×10-6)的特征,较高Sr/Y(39.05)和La/Yb(24.34)比值,具弱的负Eu(0.8)异常,ISr平均为0.7092,εNd<0。岩石学及地球化学特征分析认为皖南晚侏罗世-早白垩世早期花岗闪长岩为"C"型、高钾钙碱性埃达克岩,其发育于构造应力由挤压转变为伸展的转折期,埃达克岩浆源自印支期加厚地壳受地幔热物质上涌影响而形成的部分熔融物。The acidic magmatic rocks of late Jurassic-early Cretaceous in South Anhui are indigenous to the eastern part of Jiangnan paleouplift in the Yangtze landmass, of which the primary, rock type is calc-alkaline granodiorite with the major mineral assemblage being plagioclase＋quartz＋potassium feldspar＋amphibole_＋biotit and some accessory minerals being apatite, zircon, titanite, magnetite, and ilmenite. The magmatic rocks belong to ealc-alkaline series with geochemical characteristics of higher SIO2（66.81% ）, Al203 （ 15.23% ）, K20/Na20 （ 1.01 ） and lower TiO2（0.49% ）, MgO （ 1.49% ）, CaO （3.18%） , and P2O5 （0.18% ）. They are also obviously rich in LREE and LILE （Rb, La, Ba, Sr） , and depleted in HREE and HSFE （Nb, Ta, Zr, Y） with slightly negative 8Eu （0.8）, higher Sr/Y（ 39.05 ） and La/Yb （24.34）, lower Y （ 13.99×10^-6 ） and Yb （ 1.4 ×10^-6 ）, and meanwhile ISr = 0. 7092, eNd 〈 0. The analysis of petrological and geochemical characteristics suggests that the magmatic rocks of late Jurassic-early Cretaceous in South Anhui are ＂C＂ type, high-K calc-alkaline adakite （HKCAA） , which were formed from partial melting of the thickened lower crust by delamination in Mesozoic in eastern China.

关 键 词：埃达克岩 地球化学特征 构造环境 岩石成因 燕山期 皖南 

分 类 号：P581[天文地球—岩石学] P588[天文地球—地质学]