6块新回收沙漠陨石的矿物岩石学特征及类型划分
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摘要
干旱沙漠地区与南极冰盖均有利于陨石样品保存。2013年4—5月,通过首次新疆哈密沙漠陨石考察,回收了陨石样品47块。文中报导其中6块样品的矿物岩石学特征,并划分它们的化学-岩石类型。Arlatager004、006、0014、0022和TuzLeik001等5块样品主要由橄榄石、辉石、长石、铁镍金属和陨硫铁组成,具有典型的普通球粒陨石岩石结构特征,其球粒结构不明显,表明经历过较强的热变质,岩石类型划分为5型;根据样品中橄榄石Fa值,低钙辉石Fs值和样品的金属含量等,将Arlatager004、006、0014、0022划分为L5型普通球粒陨石;TuzLeik001划分为H5型普通球粒陨石。Kumtag005具有典型的球粒结构,结合橄榄石Fa值和低钙辉石Fs值以及岩石学特征,将其划分为L3型普通球粒陨石。根据橄榄石Fa值与其百分标准平均方差(PMD)之间的关系,将Kumtag005的岩石类型亚型划分为L 3.4。这6块样品代表了3个化学群,结合该地区回收到的其他陨石分析结果,表明新疆哈密沙漠是一个新的陨石富集区,这些沙漠陨石的发现和研究,必将极大促进中国陨石学和天体化学的发展。
Meteorite samples can be better preserved in Antarctic ice sheet and arid desert regions.Forty-seven desert meteorites were collected from Xinjiang during the meteorite expedition since April to May,2013.Petrography and mineral chemistry of the 6samples of them have been studied,in order to determine their chemical-petrographic types.Modal compositions of the Arlatager 004,006,0014,0022 and TuzLeik001meteorites are similar,mainly consisting of olivine,low-Ca pyroxene,metallic Fe-Ni and troilite.Due to intensive thermal metamorphism the spherulitic textures in the chondrules are poorly defined,with only a few fragments remaining spherulitic.The olivine and low-Ca pyroxene in these meteorites are similar in composition,which in some degree reflects the thermodynamic equilibrium during their development.According to the structures of chondrules and mineral chemistry there are 5petrographic types to be classified.The four meteorite samples(Arlatager 004,006,0014 and 0022)are classified into chemical group L,and TuzLeik001 is classified into chemical group H.Kumtag005 meteorite sample shows typical spherulitic texture,combined with its Fa value in olivine and ferrosilite content(Fs)in low Ca pyroxene and its petrographical features,it is assigned to common chondrite of L3 type.Based on Percent Mean Deviation(PMD)of Fa content of olivine and its correction with petrographic subtype of unequilibrated meteorites,Kumtag005 is subdivided as L3.4.The 6samples of meteorites belong to 3chemical groups,combining the other analytical results of meteorites collected from this region,it is suggested that the desert of Hami in Xinjiang is likely a new meteorite-enriched region.The collection and study of desert meteorite will help to promote the development of meteoritics and cosmochemistry in China.
Meteorite samples can be better preserved in Antarctic ice sheet and arid desert regions.Forty-seven desert meteorites were collected from Xinjiang during the meteorite expedition since April to May,2013.Petrography and mineral chemistry of the 6samples of them have been studied,in order to determine their chemical-petrographic types.Modal compositions of the Arlatager 004,006,0014,0022 and TuzLeik001meteorites are similar,mainly consisting of olivine,low-Ca pyroxene,metallic Fe-Ni and troilite.Due to intensive thermal metamorphism the spherulitic textures in the chondrules are poorly defined,with only a few fragments remaining spherulitic.The olivine and low-Ca pyroxene in these meteorites are similar in composition,which in some degree reflects the thermodynamic equilibrium during their development.According to the structures of chondrules and mineral chemistry there are 5petrographic types to be classified.The four meteorite samples(Arlatager 004,006,0014 and 0022)are classified into chemical group L,and TuzLeik001 is classified into chemical group H.Kumtag005 meteorite sample shows typical spherulitic texture,combined with its Fa value in olivine and ferrosilite content(Fs)in low Ca pyroxene and its petrographical features,it is assigned to common chondrite of L3 type.Based on Percent Mean Deviation(PMD)of Fa content of olivine and its correction with petrographic subtype of unequilibrated meteorites,Kumtag005 is subdivided as L3.4.The 6samples of meteorites belong to 3chemical groups,combining the other analytical results of meteorites collected from this region,it is suggested that the desert of Hami in Xinjiang is likely a new meteorite-enriched region.The collection and study of desert meteorite will help to promote the development of meteoritics and cosmochemistry in China.
引文
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[19]王道德,林杨挺,戴诚达,等.南极陨石与沙漠陨石的对比研究[J].极地研究,1999,11(2):122-135.
[20]Jull A,Wlotzka F,Brown S,et al.14 C terrestrial ages of meteorites from desert regions:Algeria and Australia[J].Meteoritics,1993,28:376-378.
[21]Ash R,Pillinger C.Carbon,nitrogen and hydrogen in Sahara chondrites:The importance of weathering[J].Meteoritics,1995,30:490-525.
[22]Bland P,Berry F,Smith T,et al.The flux of meteorites to the Earth and weathering in hot desert ordinary chondrite finds[J].Geochimica et Cosmochimica Acta,1996,60:2053-2059.
[23]Bischoff A,Weber D.Dar AL Gani 262:The first lunar meteorite from the Sahara[J].Meteoritics and Planetary Science,1997,32(Suppl):13.
[24]Mercer C,Treiman A,Joy K.New lunar meteorite Northwest Africa 2996:A window into farside lithologies and petrogenesis[J].Meteoritics and Planetary Science,2013,48:289-315.
[2]谢先德,陈鸣.动态高压下陨石矿物的冲击熔融和分离结晶及其地球化学意义[J].地学前缘,2009,16(1):134-145.
[3]陈鸣.陨石中林伍德石的形成条件对寻找地球产状林伍德石的启示[J].地学前缘,2005,12(1):23-27.
[4]Miao B,Lin Y,Ouyang Z,et al.Type distribution pattern and pairing of ordinary chondrites from Grove Mountains,Antarctica[J].Chinese Science Bulletin,2003,48:908-913.
[5]胡森,林杨挺,冯璐,等.格罗夫山普通球粒陨石的磁化率和化学分类对比研究[J].极地研究,2013,25(4):362-368.
[6]戴德求,王道德,王桂琴.南极格罗夫山100块陨石的矿物-岩石学特征[J].极地研究,2008,20(2):153-166.
[7]Lin Y,Wang D,Miao B,et al.Grove Mountains(GRV)99027:A new Martian meteorite[J].Chinese Science Bulletin,2003,48:1771-1774.
[8]Lin Y,Hu S,Miao B,et al.Grove Mountains 020090enriched lherzolitic shergottite:A two-stage formation model[J].Meteoritics&Planetary Science,2013,48:1572-1589.
[9]Miao B,Ouyang Z,Wang D,et al.A new Martian meteorite from Antarctica:Grove Mountains(GRV)020090[J].Acta Geologica Sinica,2004,78:1034-1041.
[10]Dai D,Lin Y,Miao B,et al.Ca-,Al-rich inclusions in three new carbonaceous chondrites from the Grove Mountains,Antarctica:New evidence for a similar origin of the objects in various groups of chondrites[J].Acta Geologica Sinica,2004,78:1042-1051.
[11]Van S,Wood J.A chemical-petrologic classification for the chondritic meteorites[J].Geochimica et Cosmochimica Acta,1967,31:747-765.
[12]Rubin A.Kamacite and olivine in ordinary chondrites:Intergroup and intragroup relationships[J].Geochimica et Cosmochimica Acta,1990,54:1217-1232.
[13]缪秉魁,林杨挺,欧阳自远,等.南极格罗夫山陨石岩石学特征:II:平衡型普通球粒陨石[J].极地研究,2002,14(4):288-299.
[14]Lu R,Miao B,Wang G,et al.Classification of 24new ordinary chondrites form the Grove Mountains,Anarctica[J].Acta Geologica Sinica,2004,78:1052-1059.
[15]缪秉魁,林杨挺,欧阳自远,等.南极格罗夫山陨石岩石学特征:I:非平衡L3型普通球粒陨石[J].极地研究,2002,14(4):276-287.
[16]戴德求,林杨挺,王道德,等.南极格罗夫山6块非平衡型普通球粒陨石的矿物-岩石学特征[J].矿物学报,2009,29(3):405-412.
[17]Sears D,Grossman J,Melcher C.Chemical and physical studies of type 3chondrites,I:Metamorphism related studies of Antarctic and other type 3 ordinary chondrites[J].Geochimica et Cosmochimica Acta,1982,46:2471-2481.
[18]Sears D,Grossman J,Melcher C,et al.Measuring metamorphic history of unequilibrated ordinary chondrites[J].Nature,1980,287:791-795.
[19]王道德,林杨挺,戴诚达,等.南极陨石与沙漠陨石的对比研究[J].极地研究,1999,11(2):122-135.
[20]Jull A,Wlotzka F,Brown S,et al.14 C terrestrial ages of meteorites from desert regions:Algeria and Australia[J].Meteoritics,1993,28:376-378.
[21]Ash R,Pillinger C.Carbon,nitrogen and hydrogen in Sahara chondrites:The importance of weathering[J].Meteoritics,1995,30:490-525.
[22]Bland P,Berry F,Smith T,et al.The flux of meteorites to the Earth and weathering in hot desert ordinary chondrite finds[J].Geochimica et Cosmochimica Acta,1996,60:2053-2059.
[23]Bischoff A,Weber D.Dar AL Gani 262:The first lunar meteorite from the Sahara[J].Meteoritics and Planetary Science,1997,32(Suppl):13.
[24]Mercer C,Treiman A,Joy K.New lunar meteorite Northwest Africa 2996:A window into farside lithologies and petrogenesis[J].Meteoritics and Planetary Science,2013,48:289-315.