摘要
山东蒙阴科马提岩具有典型的鬣刺结构,高镁低钛,铝不亏损,具有正的 Rb、Ba、Sr、U 异常,轻稀土元素亏损,重稀土元素平坦,稀土元素总量很低,高场强元素与稀土元素发生分异,Nb/Nb＞1,与加拿大蒙罗镇科马提岩地球化学特征和同位素特征相似。研究表明,蒙阴科马提岩可能起源于长期亏损的地幔源区,岩浆不可能来源于以橄榄石、辉石和石榴石(或者 majorite)为主要矿物相的地幔源区。最新 Sm-Nd 同位素研究显示,蒙阴科马提岩样品的εNd 值为-0.4～+3.6,新鲜样品一般为+3.3,也证实了科马提岩来自长期亏损的地幔源区,并且地幔柱在上升过程中受到地壳混染程度很小,推测研究区科马提岩的喷出可能是新太古代大陆增生事件的重要组成部分。
Mengyin komatiites are characterized by typical spinifex texture, high MgO, low TiO2, and undepleted Al. They show positive Rb, Ba, Sr and U anomalies, depleted LREE, fiat HREE and low total REE content. There occurs ffactionation of HFSE from REE, and Nb/Nb^＊ is positive. These data indicate that the source of komatiites is depleted in LREE and enriched in HFSE. Fractionation of HFSE from REE also shows that the plume could not have come from the mantle source area where olivine, pyroxene and garnet or majoritite were dominant. The latest Sm-Nd isotopic data of Mengyin komatiites not only prove that komatiites were derived from a prolonged depleted mantle but also indicate that the plume only underwent very insignificant assimilation of old continental crust. It is inferred that such a magmatic event might have constituted a component part of the continental growth in late Archean.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2006年第2期119-126,共8页
Acta Petrologica et Mineralogica
基金
国家自然科学基金(40472097)
