| 南极月球陨石MIL05035矿物学、岩石学及演化历史 |
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| 引用本文： | 陈宏毅,缪秉魁,谢兰芳,夏志鹏.南极月球陨石MIL05035矿物学、岩石学及演化历史[J].岩石学报,2015,31(4):1171-1182. |
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| 作者姓名： | 陈宏毅 缪秉魁 谢兰芳 夏志鹏 |
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| 作者单位： | 桂林理工大学, 广西隐伏金属矿产勘查重点实验室, 桂林 541004;桂林理工大学地球科学学院, 桂林 541004;桂林理工大学, 广西隐伏金属矿产勘查重点实验室, 桂林 541004;桂林理工大学地球科学学院, 桂林 541004;桂林理工大学, 广西隐伏金属矿产勘查重点实验室, 桂林 541004;桂林理工大学地球科学学院, 桂林 541004;桂林理工大学, 广西隐伏金属矿产勘查重点实验室, 桂林 541004;桂林理工大学地球科学学院, 桂林 541004 |
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| 基金项目： | 本文受国家自然科学基金项目(41173077)和广西隐伏金属矿产勘查重点实验室主任基金项目(13-A-01-02)联合资助. |
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| 摘 要： | 月球陨石MIL05035岩石类型上属于普通辉石低钛玄武岩,粗粒辉长结构,无角砾化。主要矿物为辉石(60.2%)、斜长石(27.3%)和橄榄石(6.05%),次要矿物为石英(4.36%)、钛铁矿(1.25%)和陨硫铁(0.84%),含极少量富Ti、Fe尖晶石和磷灰石,广泛发育由钙铁辉石+铁橄榄石+石英组成的后成合晶三相集合体。辉石颗粒具有明显的化学成分不均匀性和出溶片晶,核部相对贫铁钙富镁(Fs30.2-60.8Wo14.2-35.0),边部富铁钙贫镁(Fs47.5-64.9Wo22.8-44.3)。熔长石化斜长石具有微弱的成分环带,边部相对富碱金属元素(Ab9.3-12.3,Or0.31-1.03),核部则相反(Ab7.6-10.6,Or0.12-0.36),含有未熔长石化的残留斜长石。橄榄石具有粗晶橄榄石(Fa95.5-96.6)和后成合晶中细粒橄榄石(Fa88.9-93.5)两种产状。石英具有脉状、团块状和蠕虫状等产状:脉状石英大部分转变为二氧化硅玻璃,核部石英具有较宽的拉曼谱特征峰(448~502cm-1),证明其经历了冲击变质与退变质作用;团块状石英分布于粗粒橄榄石颗粒间或橄榄石与斜长石和辉石接触边界上,与斜长石构成充填结构;蠕虫状石英分布于细粒后成合晶中。粗粒辉石边部铁辉石和后成合晶中辉石成分的继承性、结构上的延续性、光学特征上的冲击暗化现象、与冲击熔脉结构上的相关性和后成合晶中发育与粗粒辉石方向几乎一致的解理等方面的证据,认为后成合晶可能由于铁辉石在冲击压力释放与温度降低后的退变质作用下分解形成。根据岩石矿物结构观察、成分分析和MELTS模拟表明该陨石母岩的岩浆演化过程可能为:母岩浆在温度降低后首先产生极少量钛铁尖晶石、其次是普通辉石和钙长石先后结晶;随着温度下降,贫钙铁普通辉石、铁钙铁辉石和铁普通辉石等在普通辉石边部大量结晶,钙长石边部分异结晶少量培长石或拉长石;随着温度继续下降,早期结晶的普通辉石析出易变辉石等出溶片晶,橄榄石在辉石和斜长石边部结晶;其后,钛铁矿和陨硫铁析出,石英沿橄榄石和钙长石等先结晶矿物裂隙充填。出露月表后强烈的冲击变质作用使斜长石几乎全部转变为熔长石、石英大部分转变为二氧化硅玻璃,并具有一系列面状变形,冲击熔脉发育,冲击变质程度至少为S5。本研究为月球的岩浆演化和冲击变质过程提供了重要证据。
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| 关 键 词： | 月球陨石 MIL05035 后成合晶 岩浆演化 冲击变质 |
| 收稿时间： | 2013/12/2 0:00:00 |
| 修稿时间： | 3/4/2015 12:00:00 AM |
Mineralogy, petrology and evolution history of Lunar meteorite MIL05035 from Antarctica |
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| CHEN HongYi,MIAO BingKui,XIE LanFang and XIA ZhiPeng.Mineralogy, petrology and evolution history of Lunar meteorite MIL05035 from Antarctica[J].Acta Petrologica Sinica,2015,31(4):1171-1182. |
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| Authors: | CHEN HongYi MIAO BingKui XIE LanFang and XIA ZhiPeng |
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| Institution: | Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;College of Earth Sciences, Guilin University of Technology, Guilin 541004, China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;College of Earth Sciences, Guilin University of Technology, Guilin 541004, China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;College of Earth Sciences, Guilin University of Technology, Guilin 541004, China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;College of Earth Sciences, Guilin University of Technology, Guilin 541004, China |
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| Abstract: | Petrologically, the Lunar meteorite Miller Range (MIL) 05035 is low-Ti augite basalt, characterized by coarse gabbro texture and massive structure, non-breccia. It consists mainly of pyroxene (60.2%), plagioclase (27.3%), olivine (6.05%), quartz (4.36%), ilmenite (1.25%), troilite (0.84%), with minor spinel enriched Fe and Ti contents and apatite. Symplectites are composed of hedenbergite, fayalite and quartz. The pyroxene grains are distinctly heterogeneous with exsolution lamellae. The cores are enriched in MgO and depleted in CaO and FeO (Fs30.2-60.8Wo14.2-35.0) contents. By contrast, the rims are rich in CaO and FeO, and depleted in MgO contents. The maskelynites are weakly heterogeneous: the rims are relatively enriched in Na2O and K2O (Ab9.3-12.3, Or0.31-1.03) and the cores are inverse (Ab7.6-10.6, Or0.12-0.36). The olivine occurs as coarse grains (Fa95.5-96.6) and fine grains (Fa88.9-93.5) in symplectites. The quartz can also be divided into three types: veined, cloddy and helminthoid. The quartz vein is changed into glass of silica. The residual quartz has wide Raman spectra (448~502cm-1) implying that these quartz experienced strong shock metamorphism and retrogressive metamorphism; cloddy quartz locates in the boundary between olivine and plagioclase or olivine, which formed filling structure with plagioclase; helminthoid quartz distributes in the symplectite assemblages. The identical composition, continued structure, impact darken Phenomena, correlation with fusion vein and dentical cleavage trend indicate that symplectites are derived from pyroxene grains induced by shock retrogressive metamorphism. The integration of petrographic observation, mineral chemistry and MELTS modelling indicate that the magma evolution processes experienced following scenarios: when the temperature decreased, spinel crystallized from parent magma, augite and anorthite were followed; as the temperature fell down, pigeonite, ferriferous augite and hedenbergite were generated, the evolution of anorthite stopped or generated a bit of bytownites and labradorites. When the temperature continued decreasing, olivine crystallized from residual magma, followed by the ilmenite and troilite, quartz was enriched in Al and K intruded along the fractures between the augite, olivine and plagioclase grains. When the rock exposed on the surface of the moon, because of the shock metamorphism, the plagioclases were transformed into maskelynites, quartz partly changed into glass and presence of fusion veins, which indicate that MIL05035 experienced strong shock metamorphism, with the degree is at least S5. This study provides convincing evidence for the early lunar magma evolution and later shock metamorphism. |
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| Keywords: | Lunar meteorite MIL05035 Symplectite Magma evolution Shock metamorphism |
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