华北断块西南部晚太古代变质铁矿建造的原岩恢复及铁矿成因类型探讨

本文试图通过主要造岩元素的岩石化学和微量元素地球化学,以八台、桂村、老羊沟地区为例,对华北断块西南部晚太古代的变质铁矿建造的原岩进行恢复,并对铁矿成因类型作一初步探讨。

PRELIMINARY STUDY ON PROTOLITH RECONSTRUCTION OF LATEARCHAEAN METAMORPHIC IRON-BEARING FORMATIONS AND IRONORE-GENESIS TYPES IN SOUTHWEST PART OF NORTH-CHINA FAULT BLOCK

Based on petrochemistry and geochemistry of both essential and trace elements, the authors of this paper have reconstructed the protoliths of Late Archaean meta-morphic iron-bearing formations and iron ore-genesis types in Patai, Kuitsun and Laoyonkou districts. It is preliminarily determined that the original rocks of Late Archaean metamorphic iron-bearing formation under study belong to a volcano-sedi- , mentary series predominated by volcanic rocks, hence supposedly a greenstone series. In Patai district, the ultramafic lava and tholeiitic volcanics form the dominant rocks constituting the basal and middle parts of typical greenstone sequence. In Kuitsun and Laoyonkou districts, a more complete Late Archaean greenstone sequence is developed with the exception of the basal part. It is inferred that the Late Archaean volcanic series of Patai district represents the volcanic product of the then spreading centre of the iron-bearing oceanic crustal basin, while that of Kuitsun and Laoyonkou districts may be regarded as the volcanic product of subduction zone in continental margin.