福建沙县壳源型晶洞花岗岩的基本特征

Characteristics of the Crust-derived Miarolite in Shaxian County, Fujian Province

福建沙县地区晶洞花岗岩的发现，在闽中尚属首次。该区内晶洞花岗岩特征与闽西南地区及闽东地区晶洞花岗岩存在较明显的差异：矿物成分相对富含黑云母；副矿物富含铁的高价氧化物及稀有、稀土矿物；岩石化学成分相对富铝、富挥发组分而贫Ca、Mg和Na；微量元素相对富Sn、Rb、Ba、Sc、U和Th；轻、重稀土比值小于1，具强烈的Eu负异常，稀土元素配分型式呈特殊的“海鸥”型。其物质来源主要为地壳物质的部分熔融，属壳源型花岗岩。岩浆经过长石的分离结晶后，在浅成的环境中侵位固结，其形成时代为白至纪。

This paper deals with the miarolite discovered in Shaxian area. Its discovery was the first time even in the middle part of Fujian Province. The characteristics of the miarolite are different from those miarolitic granites from the southwest or the east of Fujian Province. Relatively speaking,it is rich in biotite and accessory minerals such as ferric oxide,rare and rare-earth minerals etc. And its chemical composition is relatively rich in Al, volatile components, and trace elements such as Sn, Rb, Ba, Sc, U and Th etc., while poor in Ca, Mg, and Na. The LREE/HREE ratio is less than 1, and the REE distribution pattern of it looks rather like a flying seagull, with a strong negative anomaly of Eu. It is suggested that the magma be derived from the partial melting of crustal materials, thus the rock should be classified as crust-derived type granite. It is further suggested that during the Cretaceous period, the magma intruded into the shallow part of the crust and solidified there after the fractional crystallization of plagioclase.