Petrogenesis of the Northwest Africa 4734 basaltic lunar meteorite
Petrogenesis of the Northwest Africa 4734 basaltic lunar meteorite
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西北非4734玄武质月球陨石的岩石成因
DOI：
10.1016/j.gca.2012.06.024
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发表时间：
2012-09
影响因子：
5
通讯作者：
Tang G.
中科院分区：
文献类型：
--
作者：
Li X.;Li Q.;Liu Y.;Tang G.
本文报道了西北非洲（NWA）4734号月球陨石的岩相学、矿物学、微量元素丰度地球化学和Pb-Pb年代学，并与拉巴斯冰原（LAPAZ Icefield）02205/02224号低钛月球玄武岩陨石进行了比较。NWA 4734是一个未角砾化的低钛月海玄武岩，主要由次蛇绿结构的辉石（60vol%）和斜长石（30%）组成。辉石，斜长石，橄榄石表现出大的成分变化和晶粒内化学分区。NWA 4734中的辉石和斜长石具有与LAPs相似的稀土元素（REE）浓度和模式。NWA 4734的结晶年龄为3073± 15 Ma（2σ），与LAPs的结晶年龄（3039± 12 Ma）基本一致。NWA 4734和LAPs具有相似的纹理，模态丰度，矿物化学和结晶年龄，并且最有可能是月球上的源陨石坑配对。其中一颗斜锆石颗粒显示出明显的年龄和空间变化，从3349±62到3611± 62 Ma（2σ），与Zhang等人（2010）报道的同一陨石的另一颗斜锆石颗粒（3109±29到3547± 21 Ma）相似。拉曼光谱，阴极发光和化学计量的斜锆石的研究表明，这两个老颗粒不是内生的，但被父母的岩浆。平衡配分计算表明，NWA 4734斜长石结晶的母岩熔体稀土元素含量远低于全岩，表明岩浆演化为开放体系。NWA 4734可能起源于稀土元素浓度与阿波罗12号橄榄石玄武岩相似的母体熔体。岩浆可能在上升穿过月壳的过程中吸收了少量（约4wt%）的富KREEP物质。
We report the petrography, mineralogy, trace element abundance geochemistry, and Pb–Pb geochronology of the lunar meteorite Northwest Africa (NWA) 4734 and make a comparison with the LaPaz Icefield (LAP) 02205/02224 low-Ti lunar basaltic meteorites. NWA 4734 is an unbrecciated low-Ti mare basalt composed mainly of subophitic-textured pyroxene (60vol%) and plagioclase (30%). Pyroxene, plagioclase, and olivine exhibit large compositional variations and intra-grain chemical zoning. Pyroxene and plagioclase in NWA 4734 have rare earth element (REE) concentrations and patterns similar to those of the LAPs. The crystallization age of NWA 4734, determined in situ in baddeleyite, is 3073±15Ma (2σ), nearly identical to that of the LAPs (3039±12Ma). NWA 4734 and the LAPs have similar textures, modal abundances, mineral chemistry, and crystallization ages, and are most likely source-crater paired on the Moon. One baddeleyite grain in LAP 02224 displays distinctively older and spatially variable ages, from 3349±62 to 3611±62Ma (2σ), similar to another baddeleyite grain (3109±29 to 3547±21Ma) reported by Zhang et al. (2010) for the same meteorite. Raman spectra, cathodoluminescence, and stoichiometric studies of the baddeleyite suggest that the two older grains were not endogenic but were trapped by the parental magma. Equilibrium partition calculation shows that the parental melt from which the NWA 4734 plagioclase crystallized has much lower REE contents than its whole rock, indicating an open system during magma evolution. NWA 4734 could have originated from a parental melt with REE concentrations similar to that of the Apollo 12 olivine basalt. The magma likely assimilated a small amount (∼4wt%) of KREEP-rich material during its ascent through the lunar crust.
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DOI：
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发表时间：
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期刊：
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影响因子：
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