CAJ | 학술논문

东天山八大石黑云母二长花岗岩中广泛发育闪长质包体.闪长质包体与寄主花岗岩在矿物组合上不同,但两者中同类矿物的种属相似.与寄主花岗岩相比,闪长质包体的Fe、Mg、Ti、Ca含量较高,而Na、K、Si的含量较低;富HREE、Sr,贫Ba、Th、Hf、Zr.锆石LA-ICP-MS U-Pb年龄显示闪长质包体与寄主花岗岩在形成时间上非常接近(分别为301±1 Ma和298±2 Ma),表明两者均形成于早二叠世.闪长质包体和寄主花岗岩具有正的εNd(t)(+4.15和+3.06)、较低的(87Sr/86Sr)i (0.704 12和 0.704 75)和相近的模式年龄tDM(812 Ma和944 Ma),暗示其母岩浆来自新元古代时从亏损地幔分离出来的初生地壳源区.综合岩石学、地球化学和同位素等方面的对比研究,笔者认为八大石闪长质包体属于同源包体,为寄主花岗岩同源母岩浆经结晶分异作用形成的早期产物.
동천산팔대석흑운모이장화강암중엄범발육섬장질포체.섬장질포체여기주화강암재광물조합상불동,단량자중동류광물적충속상사.여기주화강암상비,섬장질포체적Fe、Mg、Ti、Ca함량교고,이Na、K、Si적함량교저;부HREE、Sr,빈Ba、Th、Hf、Zr.고석LA-ICP-MS U-Pb년령현시섬장질포체여기주화강암재형성시간상비상접근(분별위301±1 Ma화298±2 Ma),표명량자균형성우조이첩세.섬장질포체화기주화강암구유정적εNd(t)(+4.15화+3.06)、교저적(87Sr/86Sr)i (0.704 12화 0.704 75)화상근적모식년령tDM(812 Ma화944 Ma),암시기모암장래자신원고대시종우손지만분리출래적초생지각원구.종합암석학、지구화학화동위소등방면적대비연구,필자인위팔대석섬장질포체속우동원포체,위기주화강암동원모암장경결정분이작용형성적조기산물.
Dioritic enclaves are widely distributed in Badashi biotite-monzogranite of the East Tianshan Mountains. These dioritic enclaves and their host granite are different in mineral association, but species of the same mineral within them are similar to each other. In comparison with the host granite, the dioritic enclaves are higher in Fe, Mg, Ti, Ca and richer in HREE, Sr, but lower in Na, K, Si and poorer in Ba, Th, Hf, Zr. Zircon LA-ICP-MS U-Pb dating gave ages of 301±1 Ma and 298±2 Ma for the dioritic enclaves and their host granite, respectively, indicating their Early Permian emplacement. The dioritic enclaves and their host granite have positive in εNd(t) (+4.15 and+3.06) values and relatively low (87Sr/86Sr)I (0.704 12 and 0.704 75) with fairly similar model ages (tDM) (812 Ma and 944 Ma, respectively). It is suggested that the dioritic enclaves and their host granite were derived from the same parental magma that resulted from partial melting of the Neoprot-erozoic depleted-mantle-sourced juvenile crust. Petrologic, geochemical and isotopic studies prove that the Badashi dioritic enclaves are autoliths and the earlier products generated by crystal fractionation of the host granite parental magma.