Petrochemistry and recrystallization history of granulite xenoliths from the Pali-Aike volcanic field, Chile
Petrochemistry and recrystallization history of granulite xenoliths from the Pali-Aike volcanic field, Chile
复制标题
DOI：
--
复制
发表时间：
1983-12
影响因子：
3.1
通讯作者：
J. Selverstone;C. Stern
中科院分区：
文献类型：
--
作者：
J. Selverstone;C. Stern
在南美洲巴塔哥尼亚南部更新世—新近碱性玄武岩中发现的基性麻粒岩相包体，其矿物组合为斜辉石+正辉石+斜长石+或-橄榄石+或-钛磁铁矿，为无片理的麻粒岩基质。在橄榄石和斜长石彼此靠近的地方，它们被辉石和尖晶石的共生体隔开。辉石-尖晶石共长体形成于860℃，在此温度下橄榄石+斜长石生成辉石+尖晶石的反应边界发生在5-7 kbar。捕虏体被解释为存在于地壳深处约20公里处的辉长岩岩体的碎片。这与基性火成岩构成下大陆地壳的很大一部分的说法是一致的。捕虏体在寄主玄武岩中的捕获必然导致了广泛的加热，但这一事件的岩石学证据仅限于非均质分布的高温氧化效应。——修改后的期刊摘要。
Mafic granulite facies xenoliths found in the Pleistocene-Recent alkali basalts of southern Patagonia, South America, have an unfoliated granoblastic matrix with the mineral assemblage clinopyroxene + orthopyroxene + plagioclase + or - olivine + or - titanomagnetite. Wherever olivine and plagioclase are in close proximity to one another they are separated by symplectic intergrowths of pyroxenes and spinel. Two-pyroxene geothermometry indicates that the granoblastic matrix phases equilibrated at approximately 900 degrees C. The pyroxene-spinel symplectites formed at 860 degrees C, at which temperature the reaction boundary of olivine + plagioclase to produce pyroxenes + spinel occurs at 5-7 kbar. The xenoliths are interpreted as fragments of a gabbroic pluton which exists at a depth of approximately 20 km in the crust. This is consistent with suggestions that mafic igneous rocks comprise a large portion of the lower continental crust. Capture of the xenoliths in the host basalt must have resulted in extensive heating, but the petrologic evidence of this event is restricted to heterogeneously distributed high temperature oxidation effects.--Modified journal abstract.