| 浙江青田花岗岩中岩石包体特征及成因 |
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| 引用本文： | 董传万,彭亚鸣.浙江青田花岗岩中岩石包体特征及成因[J].岩石矿物学杂志,1992,11(1):21-31. |
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| 作者姓名： | 董传万 彭亚鸣 |
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| 作者单位： | 浙江大学地球科学系，南京大学地球科学系 杭州 310027，南京 210008 |
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| 摘 要： | 浙江青田燕山晚期黑云母花岗岩中有许多石英闪长质岩石包体,它们大小不一,形态各异,以微细粒结构、具冷凝边构造、并发育针状磷灰石为特征。岩石包体与寄主花岗岩的主要氧化物、微量元素的变化趋势呈线性关系。岩石学、矿物学、岩石化学及地球化学等特征的研究表明,石英闪长质岩石包体属淬冷包体,由玄武质岩浆和花岗质岩浆通过不均匀的混合作用而形成。
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| 关 键 词： | 花岗岩 岩石 包体 成因 浙江 |
The Features and Origin of the Enclaves in the Qingtian Granite,Zhejiang Province |
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| Dong Chuanwan,Peng Yaming.The Features and Origin of the Enclaves in the Qingtian Granite,Zhejiang Province[J].Acta Petrologica Et Mineralogica,1992,11(1):21-31. |
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| Authors: | Dong Chuanwan Peng Yaming |
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| Institution: | Dong Chuanwan,Peng Yaming Department of Earth Sciences,Zhejiang University,HangZhou 310027 Department of Earth Sciences,Nanjing University,Nanjing 210008 |
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| Abstract: | There are a lot of microgranular enclaves in the late Yanshanian Qingtianbiotite granite in southeast Zhejiang Province. The enclaves are generallyround or sub-round with diameters from 10 to 20 cm. They are usually scat-tered but some of them occur in groups in the granite. The enclaves are often gray or dark-gray in colour. Generally, there areclear boundaries between the enclaves and host granite, but some show diffu-sion contact. A few of enclaves show fine-grained margins, i. e. chilled mar-gins. The enclaves are mainly composed of plagioclase(An=37), hornblende, ??biotite, quartz, and K-feldspar. The plagioclase is zoned. Quartz and K-fel-dspar fill in the interval betWeen plagioclase, or enclose the microcrystalplagioclase and hornblendes to form intergranular texture which is similarto that of dolerite, or poikilitic texture. The accessory minerals include mag-netite, ilmenite, apatite, sphene, etc. The apatite is very long with theratio of length to width up to 30:1, and has clear basal cleavage. Accordingto Wylie this kind of apatite is formed by sudden cooling of the magmaoc-existing with the apatite. Chemically, the enclaves belong to the calc-alkline rock serieswith SiO_2=60-68%, Na_2O>K_2O, and A/NKC<1. In comparison to the host granite,the quartz-dioritic enclaves have higher contents of Ti, V, Cr, Co, Ni, Zr,Sr, Ca, Mg and REE. On the variation diagrams of major oxides versus SiO_2of the enclaves and the host granite, the plots show linear trends, and sodo some pairs of trace-elements divided hy other trace-elements. There are different hypotheses about the origin of microgranular enclavein granitic rocks. The enclave may be regarded as xenolith, or the relictphase of partial melting of basement rocks, or a product of magma mixing,and so on. Based on field observations and petrological, geochemical, andmineralogical features of enclaves, the authors believe that magma mixingtheory is most suitable for explaining the characteristics of the quartz-dio-ritic enclaves in the Qingtian biotite granite, namely, they were the productsof mechanical mingling between basaltic or intermediate-basic magma andgranitic magma. |
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| Keywords: | host granite enclaves quenched enclaves magma mingling |
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