白银市乌金峡一带志留纪中酸性侵入岩特征及构造意义

通过对甘肃省白银市乌金峡一带中酸性侵入体的地质学、岩石化学、地球化学等研究,发现该侵入体高w(Na2O),低w(MgO)、w(TFeO)、w(Al2O3)、w(K2O),w(TiO2)、w(MgO)、w(MnO)、w(TFeO)、w(CaO)、w(K2O)与w(SiO2)负相关,w(Na2O)与w(SiO2)正相关;轻、重稀土都有分异,但轻稀土更明显,且轻稀土富集,δ(Eu)轻度正异常—亏损,大离子亲石元素Ba、Th、Sr富集,Rb、Li亏损,属同源岩浆演化的产物。岩浆结晶温度为700℃～890℃。形成时代大致为奥陶纪中晚期,属于岛弧构造环境,为中祁连地块和北祁连洋间相互作用的结果。

Chracteristic and Tectonic Significance of Intermediate-Acid Intrusive Rock in Wujinxia Area of Baiyin City

Through the geological, petrochemical and geochemical research on intermediate acid intrusive rock located inWujinxia area of Baiyin City in Gansu Province, it is found that w(Na2O)are high, meanwhile, w(MgO), w(TFeO),w(Al2O3)and w(K2O)are low,w(TiO2),w(MgO),w(MnO),w(TFeO),w(CaO),w(K2O)and w(SiO2)are negativecorrelated, w(Na2O) and w(SiO2) are positive correlated, LREE and HREE are differentiated, LREEs are moreobviously enriched,andδ(Eu)are depleted, large ion lithophile elements such as Ba, Th,Sr are enriched, Rb and Li arepoor. The temperature of magmatic crystallization is from 700 ℃ to 890 ℃ . The intrusinve body was the product ofcomagmatic evolution during the mutual interaction of Central Qilian massif and Qilian ocean in the island-arc tectonicenvironment of middle-to later Ordovician period.