| 花岗质岩石的交代结构构造及其成因意义 |
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| THE CLASSIFICATION OF METASOMATIC REPLACEMENT FABRICS OF GRANITIC ROCKS AND ITS GENETIC SIGNIFICANCE |
| Metasomatism plays an important role in the formation of granitic rocks, and is generally considered as one of the most important criteria in identifying its migmatic origin. However, metasomatism exists also as an important factor in magmatic ones, although its significance has long been argued.The evidence of metasomatism in granitic rocks is exhibited by the app-earence of corrosion fabrics and replacement of minerals at the expense of old ones as the result of metasomatic alteration of pre-existing metamorphic rocks or earlier products of newly-born magmas in the course of anatexis.There is a marked tendency showing the successive replacement changes of minerals, especially the alkali metasomatism of plagioclase in the course of anatectic formation of granites of various genetic types. Different kinds of replacemenn fabrics of potassium metasomatism with respect to plagioclase have been demonstrated and discussed.As a whole, the replacement fabrics from the migmatization to the initiation of anatextic melts and finally to the emergence of magma may constitute a replacement fabrics series which may be classified as:1 ) Replacement mosaic texture, mostly developed in Migmatic agglomera-tis recrystallzation stage;2 ) Mosaic replacement texture,developed mainly in migmatization stage;3 ) Replacement gneissic texture, mostly developed with the connection of the formation of migmatic granites;4 ) Hypidiomorphic replacement texture, mainly developed in the mag-matic granites of contamination type.It seems that the appearence of metasomatism in granitic rocks is caused by the volatile constituents involved in the anatexitic process. In fact, crustal rocks could be transformed into autochthonous migmatic granites by means of pore fluids; they could be evolved into different types of migtna plutons by the emplacement of volatile-bearing migma either; and if the volatile constituents ane present in the magma system, there may also occur some replacement pheonomenon known as hypidiomorphic replacement texture or replacement Kporphyroblastic texture in granitic batholithes. |
| DONG Shen-bao,HE Gao-pin.1987.THE CLASSIFICATION OF METASOMATIC REPLACEMENT FABRICS OF GRANITIC ROCKS AND ITS GENETIC SIGNIFICANCE[J].Acta Geoscientica Sinica,9(2):71-82. |
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