摘要
岚山头一带含霓石碱长花岗岩分布在胶南造山带的南段，是华北板块与扬子板块碰撞晚期在引张环境下形成的A型花岗岩。该花岗岩含有霓石、钠闪石、微斜长石、钠长石等碱性矿物；K2O和Na2O的含量为8．4％～9．6％，H2O＋少于0．16％，具有富碱、贫水的特点；稀土元素总量在262．19×10－6～313．23×10－6范围内，87Sr／86Sr初始比值为0．72902；Pb－Pb同位素年龄值为622．7Ma。含霓石碱长花岗岩体内含有较多的柯石英榴辉岩、榴辉岩包体。柯石英榴辉岩为超高压变质作用的产物，而其围岩（含霓石碱长花岗岩）却保存下了岩浆成因的霓石，处于富Na、Al、Si变质环境中，未出现硬玉或硬玉分子较高的绿辉石。这说明含霓石碱长花岗岩没有经受过超高压变质作用，即柯石英榴辉岩相对其围岩而言是外来的。
The aegirine-bearing alkaline granite in Lanshantou is distributed in the south of the Jiaonan orogenic belt. It is A-type granite fomed in the extension environment of the late stage of the collision between the north China plate and the Yangtz plate. Alkaline minerals t such as aegirine, riebeckite, microcline and albite are found in it. The contents of K2O and Na2O range from 8. 4 %～9. 6 % , and H2O+is less than 0. 16 % ; thus,we can say it is rich in alkali and poor in water; the contents of LIL elements, such as Ba and REE are very high. The total amount of REE is 262. 19～313. 23mg/g, and the initial ratio of 87Sr/86Sr is 0. 72902;the Pb-Pb isotope age of the granite is 622. 7Ma. The aegirine-bearing alkaline granite contains inclusions of coesite-bearing eclogite and eclogite. Coesite-bearing eclogite is the product of ultrahigh-pressure metamorphism,while its country rock (aegirine-bearing alkaline granite) has preserved aegirine of magmatic origin. Under metamorphic environment rich in Na, Al and Si, the absence of jadeite and omphacite which contains higher jadeite moleculars in the aegirine-bearing granite indicates that the aegirine-bearing alkaline granite has not experienced ultrahigh pressure metamorphism. That is to say,the coesite-bearing eclogite is exotic relative to its country rock.
出处
《山东地质》
1997年第1期50-59,共10页
Geology of Shandong
