摘要
迁西群以混合杂岩为主,占岩石出露面积80%以上。变质岩零星分布在混合岩中。变质岩系由麻粒岩、黑云(辉石、角闪石)斜长片麻岩、变粒岩及黑云母(石榴石)浅粒岩为主体的岩石组成。岩系下部出现较多暗色麻粒岩,上部具薄层夕线石碱长片麻岩。为麻粒岩相区域变质岩石。其变质原岩自下而上由中基性火山沉积岩——中性火山沉积岩——酸性火山岩及火山沉积岩、杂砂岩夹薄层泥质沉积岩组成,伴有基性层状或脉状侵入体及小型超镁铁质岩体。在上部岩层中,赋存有条带状磁铁石英岩大型铁矿床。工作区岩层厚度4000公尺以上。
Archaeozoic migmatites constitue the main part of the Qian-an Group. They are chiefly of migmatitic gneisses.Petrographically the geneisses may be classified intogrey pyroxene-plagioclase migmatite & red biotite migmatite, representing granueific litic & light granulitic original rocks respectively. The referred migmatites are thought to be resulted from anatexis. The following re'evaut data are documented:1 . The migmatites were conditioned by a granu'ite facies of metomorphism held at temperature of 683-744°c and a pressure of 5-7kb.2. Mineralogically the migmatites are imprinted by the nature of their original rocks. In texture the cumulorecrystallization, the remelt-rc replacemeut crystallization & various interg-rowth produced in the process of remelting are identified.3. In the course of migmatite evolution, the bulk chemical coposition was main atined without change except there were apparent redistribution of the chemicalelements, such as the concentration of K, Si in the migmatites, the born of some minimum melts forming the granulitic veinrocks and the cumulation of Ca, Mg and Fe in new-born dark minerals.4. Deduced fvom the mineral geothermometry and melting point determined for the migmatites, the temperature in the progression of the migmatization is supposed to be 680-7l4℃ at the early stage, and 46013 at the final stage. This means the temperature that the reginal partial meeting he'd is in accordance with that of the grauulite facies metamorphism.5. The time of migmatization may be distinquished in 3 stages:the early stage, whence the recystallization of the selective melts and of the infusible elements took place; the middle stage, whence the recrystallization was led in the process of replacement holding between the minimun melte and the residues, It was in this stage the migmatites were essentially formed. The late stage, i. e. the hydrothermal stage, whence some of the high temperature mineral assemblage might be defraded or alterated, The thmperatures at which the different stages taking p
出处
《吉林大学学报（地球科学版）》
EI
CAS
1982年第3期59-76,共18页
Journal of Jilin University：Earth Science Edition
