东篱科研大数据发现系统（DRDS）

位置：成果数据库 > 期刊 > 期刊详情页

月海玄武岩与月球演化

ISSN号：0379-1726
期刊名称：《地球化学》
时间：0
分类：P184.1[天文地球—天文学] P597[天文地球—地球化学;天文地球—地质学]
作者机构：[1]中国科学院同位素年代学和地球化学重点实验室．中国科学院广州地球化学研究所,广东广州510640
相关基金：基金项目：国家自然科学基金（40721063）;中国科学院知识创新工程方向性项目（KZCX2-Yw-T004）

作者：徐义刚[1]

关键词：矿物学, 地球化学, 月海玄武岩, 岩浆海, KREEP, 月球演化, mineralogy, geochemistry, mare basalt, lunar magma ocean, KREEP, evolution of the Moon

中文摘要：

月海玄武岩主要产于月球近边的盆地中，覆盖面积为月球表面的l％，其形成年龄多在39～31亿年之间，是各类月岩中最年轻的。与地球玄武岩相似，月海玄武岩由斜长石、辉石和橄榄石组成，但它们比地球玄武岩具有更低的Mg#、A1：0，、K和Na含量．高的FeO含量（大于16％）和变化范围大的TiO2含量（小于l％到大于13％）。根据TiO2含量的变化，月海玄武岩分成高Ti（〉6％），低Ti（1．5％〈TiO：〈6％）以及极低Ti（〈1．5％）三类。所有月海玄武岩都具有Eu负异常，并亏损挥发性元素和亲铁元素。月海玄武岩的同位素特征指示其至少为三个组分混合的产物：（1）高：238U／204Pb、高87Sr／86Sr和负εNd组分，可能是岩浆海分异的残余岩浆即KREEP；（2）低：238U／204Pb、低87Sr／86sr和正εNd组分，来源于原始月幔，其熔融产物为低Ⅱ玄武岩；（3）中等87Sr／86Sr和εNd组分，位于月幔的顶部，经历了岩浆海（洋）过程中形成的堆晶物质的再熔融，还可能受到了陨击事件的影响，其熔融产物是高Ti玄武岩。月海玄武岩的元素和同位素地球化学性质支持岩浆海的假说，其源区的形成与岩浆海的分异密切相关，并经历了三个阶段：（a）岩浆海阶段，通过岩浆海的结晶分异形成顶部为斜长岩月壳，中间为高Ⅱ、富钛铁矿层，底部为巨厚的硅酸盐低Ti层的三层壳幔结构；（b）富钛铁矿堆晶岩（携带少量残余熔体）因密度大而下沉至下部的硅酸盐月幔（400km以下）；（C）月幔中这些不同源区的岩石发生减压熔融。早期由较浅的低熔点组分熔融形成低K高Ti玄武岩，之后形成来源较深的高Ti玄武岩和低Ti玄武岩。

英文摘要：

Mare basalts are mainly distributed in basins in the near-earth side, occupying 〈1% of the volume of the Moon. Most mare basalts were emplaced during 3.9- 3.1 Ga, thus being young by lunar standards. Like basaltic rocks on Earth, mare basalts are composed of plagioclase, pyroxene and olivine. However, they are lower in Mg#, AlzOB, Na and K, higher in FeO contents than the terrestrial basalts. TiO2 contents in mare basalts are extremely varied, ranging fi＇om 〈 1% to 〉 13%. Based on the TiO2 variation, mare basalts are classified into three groups, i.e., highTi （〉 6%）, lowTi （1.5% 〈TIO2〈6%） and extremely lowTi （〈1.5%） basalts. All the mare basalts are characterized by negative Eu anomaly and are deficient in volatile and siderophile elements. Isotopic systematics of mare basalts indicate at least three components：（1） a component with high 238U/204pb, high 87Sr/86Sr and negative end values, likely represented by KREEP residuum of a global lunar magma ocean; （2） a ＂primordial＂ deep mantle source with 23sU/204pb typical of Earth, low 87Sr/86Sr and positive end values; and （3） a shallow mantle reservoir that has similar 238U/2044pb values to the second, intermediate end and low to intermediate 87Sr/86Sr values. The typical melting products of the second and third components are low-Ti and high-Ti basalts, respectively. Elemental and isotopic characteristics of mare basalts are in support of the lunar magma ocean hypothesis and suggest a close relationship between their source formation and differentiation of magma ocean. The sources for the mare basahs were likely fomled in a three-stage process. First, a global lunar magma ocean differentiated into a plagioclase-rich flotation crust, a thin high-Ti source and a thick low-Ti source consisting mostly of variable proportions of olivine and orthopyroxene with minor clinopyroxene. Second, the denser ilmenite-rich layer, probably accompanied by variable amount of KREEP-type magma residuum, sank into the lower silicate layer o