桦甸太古代变质层状侵入体的岩石学及地球化学

东北桦甸深变质层状岩体经历了中—深度变质作用和强烈的挤压变形。它可分为角闪岩、辉长岩、浅色辉长岩、斜长岩、(花岗)闪长岩等分异岩层。随着分异层序的变化,MgO、FeO~*、Ni等依次增高,而SiO_2、Na_2O、K_2O等依次降低。它们具有相似的、轻重REE较为分离的分布型式,(Sm/Yb)N约4—5,Eu/Eu~*约0.9—1.3,YbN约0.8.REE和Zr、V、Y、Cr等的地化特点显示它们是一个古老层状辉长岩体的残片和岩浆分异结晶的产物。

PETROLOGY AND GEOCHEMISTRY OF THE HUADIAN HIGH-GRADE METAMORPHOSED LAYERED GABBROIC COMPLEXES, NE CHINA

Layered ultramafic-gabbro bodies occur widely in the Archaean high-grade gneiss terrains, this is a very important Archaean rock association. A large ultramafic-gabbro body have been discovered recently, which occurs in Huadian NE China. They were metamorphosed at granulite and high amphibolite facies, and tectonically deformed and broken up during metamorphism. It can be divided into hornblendite, gabbro, leuco-gabbro, anorthosite, diorite and granodiorite layers. Each rhythmic unit shows decreasing MgO, FeO, Ni and increasing SiO_2, Na_2O, K_2O with stratigraphic height. In ultramafic rocks, SiO_2 varies from 40 to 45 wt.%, while SiO_2 ccntent of the gabbros ranges from 45 to 53 wt.%, SiO_2 content of the diorite-granodiorite, from 55 to 61 wt.%. They have extremely similar REE distribution patterns with fractional patterns of LREE and HREE, and negative Eu anomalies. Sm_N/Yb_N is about 4-5, Eu/Eu~* is about 9-13, Yb_N is about 8. Studies of REE and trace elements Zr, V, Y. Cr, Ni ets show that these comagmatic rocks are fragments of an old layered bady and products of fractional crystallization of gabbro magma.