摘要
辉石和长石是玄武岩的主要矿物成分,辉石为含Fe,Ti,V等元素矿物,长石为富铝矿物。二叠系玄武岩火山间歇期间,大气中的强酸性气体被雨水转移到地表水之后就变为饱含CO_2气雨水。在温暖至湿热的气候条件下,饱含CO_2气雨水造成玄武岩中的富铝矿物分解首先形成高岭石、埃洛石等粘土矿物,而Fe,Ti,V等元素也因辉石等矿物的分解而迁移出来,并在高岭石等粘土矿物形成的吸附障中富集。与此同时,含铁矿物氧化分解形成针铁矿及赤铁矿。在雨量充足、海侵事件等的作用下,水位较高,风化壳下部处于较还原的条件下,铁被还原成易溶的二价状态或在有机质的作用下迁出风化壳,并在合适的地质条件(向斜构造)下富集,造成Fe(Ti,V)—铝等元素分离,并伴随铁矿、铝土矿的形成。
The pyroxene and feldspar are main components of the basalt.As well known,the pyroxene always contains Fe,Ti,V etc.and the feldspar is generally rich in Al.The strong acidic gases in the air were transferred by the rainwater into surface water which was saturated with CO_2 during the intervals after basaltic volcanisms in Permian.Under a sticky climate,the Al-rich minerals(e.g.feldspar) in basalts were altered,by the CO_2-rich surface water,and firstly broke up into clay minerals,such as kaolinite and halloysite which could concentrate Fe,Ti and V resulted from the decomposition of pyroxenes.Meanwhile,the Fe-bearing minerals were oxidized into goethites and hematites.At a high water level due to adequate rainfall ore marine transgression,it became relatively reducing at the bottom of weathering crust.Therein,Fe was reduced to soluble Fe^(2+),which was migrated out of the crust and finally concentrate at favored geological conditions.Just this process resulted in separation of Fe(V,Ti)and Al,accompanying occurrences of the iron and bauxite deposits.
出处
《地球科学进展》
CAS
CSCD
北大核心
2012年第S1期144-148,共5页
Advances in Earth Science
关键词
玄武岩
风化壳
地球化学
贵州西部
Basalt
Weathering crust
Geochemistry
Western Guizhou Province
