河南鲁山太华群两类斜长角闪岩地球化学对比及其构造环境

河南鲁山早前寒武纪太华群中分布着两类斜长角闪岩：一类为正常斜长角闪岩，主要产于晚太古代下太华群荡泽河组；另一类为富钠斜长角闪岩，产于古元古代上太华群雪花沟组。两类岩石外表特征和矿物成分相近似，但化学成分明显不同。正常斜长角闪岩具较低的Na2O（1．96％－2．86％）、K2O（0．24％－0．64％）、Ti、Y、Zr、Hf和REE含量，而富钠的斜长角闪岩以较高的Na2O（3．31％－5．50％）、K2O（0．47％－1．41％）、Ti、Y、Zr、Hf和REE含量为特征。通过对比研究，认为前者为拉斑玄武岩，成分与现代洋壳中发现的低钾拉斑玄武岩相似；后者主要为富钠的基性火山岩，与陆内裂谷或地槽区产出的细碧岩相似，表明本区Pt／Ar转变过程中的构造环境发生了重大变化。这一转变过程初步认为是本区晚太古代地壳上升所引起的长期风化剥蚀作用的结果。

GEOCHIMICAL COMPARING OF TWO TYPES OF AMPHIBOLITES WITHIN TAIHUA GROUP IN LUSHAN COUNTY,HENAN PROVINCE AND THEIR TECTONIC SETTINGS

Two types of amphibolitic rocks are distributed over early Precambrian Taihua Group in Lushan County, Henan Province. The first type is normal amphibolites occurring mainly in Dangzehe Formation of lower Taihua Group (Late Archaean Era);the second is sodium-rich amphibolites which was discovered in Xuehuagou Formation of upper Taihua Group (probably Early Proterozoic Era). The two types of amphibolites are similar in many external features and mineral composition each other,but the chemical compositions between them are obviously different. The normal amphibolites have lower contents of Na2O (1.96%-2.86%), K2O (0.24%-0.64%), Ti,Y,Zr, Hf and REE, whereas the sudium-rich amphibolites are characterized by richer Na2O (3.31%-5.50%), K2O (0.47%-1.41%), Ti, Y, Zr, Hf and REE contents. By means of correlation studies of the various geochemical diagrams, it is suggested that the former is of tholeiitic series resembling compositionally the low-K tholeiite discovered in the recent oceanic crust; the latter is mainly sodium-rich basic volcanic rocks, the compositions of which are similar to a spilite evolved in intracontinental rift or geosynclinal area. It is showed that tremendous changes of the structural setting had taken place during the transformation from Late Archaean Era to Early Proterozoic Era in mis region. This conversion process is preliminarily considered as a result of the long-term weathering and denudation caused in the course of rising of the late Archaean crust.