摘要
初步研究表明,霍邱群含铁岩系的地球化学特征可与世界太古宙沉积岩系相类比。与铁矿成因关系密切的变玄武岩稀土分布模式为TH_2型,变基性凝灰岩为轻稀土富集型,变沉积岩具轻稀土富集分布型式。
The Late Archean iron-bearing series in the Huoqiu Group is covered by the Quaternary system. The iron formation has reached amphibolite-facies metamorphism.The original rocks of the Huoqiu Group consist of intermediate-basic pyroclastic rocks in the lower part with tholeiite interbeds and of graywacke and pelite intercalated with banded magnetite quartzite, carbonate rocks and metabasalts in the upper part.The major element geochemistry of clastic sediments show abundances of Fe, Mg, and Na but depletion in Si and K. Their element contents and ratios are indicative of volcanic deri-vation.The REE distribution patterns in metabasalts show slight LREE enrichment and slight HREE depletion. The case is much similar to that for TH2 type.Basic tuffs are characterized by slight HREE enrichment with a small Eu anomaly. The ratio of La/Yb is 3 and that of Sr/Ba ranges from 1.2 to 0.45. The REE distribution pat-terns in metasedimentary rocks are characterized by strong HREE depletion with higher Cr/Ni, Sr/Ba<1 and σEu≥l. Their REE contents and ratios are comparable with those for the Archean sedimentary rocks known in the world.
出处
《地球化学》
CAS
1988年第4期336-342,共7页
Geochimica
