球粒陨石难熔包体中贵金属的矿物岩石学分析 对太阳星云演化的启示.pdf

552Vol.55 No.2 2014 3ACTA ASTRONOMICA SINICAMar., 2014 ∗ 1,2 1 2,3† 1430074 2210008 3210008 Ca, Al-rich Inclusion, CAI ,, ,.ǑǑ ,CVNWA 2140,CAI ., ,,Ǒ . ,,, P148; A 1 ,Ǒ ., ,, ,,  [1]. CAIǑ ,, [2−3]. ,ReOsIrMoRuPtRh W [4]. Palme [4] CAI 20 mWReOsIrMoRuPtRh, . Ǒ, 2013-03-31, 2013-10-14 ∗4117307641273079℄ † wbxu 10655 [5]. CAI, CAI. OsIrRuRhPtPd8 WMoRe. 3, [4,6−7]; , [8]; , CAI [9−11].  .,, , . 2 ,. . .SEMǑHitachi S3400N-II,Ǒ 15 kV,5 nm,ǑOxford INCA., . . 3 3.1 NWA 21402003 , 2008 12 ,Ǒ314 g,CV3 .CV3,, Mg/Si [12−13]. NWA 2140 , ,60∼70Ǒ, . NWA 2140,ǑPMO-1024PMO-1031. 0.7∼3 mm,Ǒ,Ǒ. ,,8 mm,7 mm, ,,Ǒ, 1ab,. ,,,Ǒ ,200∼800 m,ǑB1 [14]. ,20 m. ,.1Ǒ. . 2107 1a NWA 2140 PMO-1024CAI; b NWA 2140 PMO-1031CAI, Ǒ Fig.1a CAI in NWA 2140 PMO-1024; b CAI in NWA 2140 PMO-1031, another section of the same CAI shown in Fig.1a ,, 2.,Ǒ. 2 Fig.2A closeup view of the distribution of noble metal alloys in the CAI CAI.1, ,ǑI.ǑIFeNi, FeNi,3a;2,FeNi , ,II,3b. 10855 3a I; b II Fig.3a Noble metal alloys of Group I; b Noble metal alloys of Group II 3.2 3.2.1 FeNi, .,4. ,, ., . . 51,, 12. 1I Table 1The composition of alloys of Group I Element Mass fraction/ Average Alloy 1Alloy 2Alloy 3Alloy 4Alloy 5 Fe3.92.52.010.99.15.7 Ni2.92.61.627.05.58.0 Mo18.72.115.2-19. 611.1 Ru22.424.630.430.827.927.2 Os13.147.942.627.316.629.5 Ir16.020.45.54.121.313.5 Pt18.0----3.6 W--2.7--0.5 Rh5.1----1.0 2109 4OsMoRuPtNiFeCo [4] Fig.4Theoretical condensation curves for noble metal elements Os, Mo, Ru, Pt, Ni, Fe, and Co condensing in an alloy[4] 2II Table 2The composition of alloys of Group II Element Mass fraction/ Average Alloy 1Alloy 2Alloy 3Alloy 4Alloy 5 Fe2.73.05.77.42.44.2 Ni4.711.94.516.33.28.1 Mo6.518.13.43.76.37.6 Ru45.231.746.129.124.935.4 Os26.912.226.312.650.825.8 Ir14.023.111.78.312.413.9 Pt---19.6-19.6 W------ Rh--2.4--2.4 , 4,.Palme [4] ,EǑ αE 1 CH2 γE Ptot 13 P i1 αiCi 10− A TB −1 . atomic fractionǑXE αECE 13 P i1 αiCi , Ci 11055 ; γE; Ptot,10 Pa[7]; T Ǒ; ABǑ.Campbell [15]. . ,., . Matlab.Ǒ,. Ǒ,Ǒ,. ,,5. 5 . 5 Fig.5The comparison between the equilibrium calculations and measured compositions of noble metal alloys main elements are plotted ,I 1 ,. 2 ,Ǒ1450∼1600 K. 3 Mo. 4 IrǑ,Ǒ. III 1 2111 ,. 2MoIr Ru. 3 Ǒ1420∼1580 K. ,W;I FeNi, NiFe;II NiǑFe,, Ni/Fe4 1, Ǒ. 3.2.2 6,, . Ǒ, [16−17]. ,Ǒ [9−10]. 6 Fig.6A whitlockite in CAI adjacent to noble metal alloys the dark grey area in the center of the light grey grain 4 4.1 , IǑ1450∼1600 K, .II, ,Ǒ.Ǒ1420∼1580 K.Ǒ II,. 4.1.1 I I,WMoIrRuRhPtNiFeCoPd 11255 ,OsRu, FeNi, Mo ,. [7]. 5OsRu . IǑ, Ǒ,ǑI , [18]. IIr,Ir , Ir [19−20]. , Ir .RuǑ, .,NiFe,1 4Ni,, FeNiǑ,3a.NiFe .OsRu. IrRuOs ,,, OsǑ ,OsRuIr., IrǑ., ,Ir. I,, Ǒ. WMoǑ. WMo ,,,W, Mo,ReOsRuIrPt, WMo [21−22]. ,Mo,, Ǒ. Berg [7] Murchison5,OsRu FeǑ,Ir, IMurchison ., MurchisonIr, MoW Ǒ,,I Murchison., Murchison, Ǒ,. 4.1.2 II II, MoIrRuǑ, ,Ǒ. CAI. . , 2113 ,,. IIǑ,Ǒ. Ǒ,, , [9,11]. , ǑǑ. WMo ,ǑWMo,Mo ,. Palme [10] Fuchs [23] Allende ,ǑW,Mo,MoS2, , PtRhNi-Fe,OsRu .,II ., .,Ǒ . 4.2 , ,. Lauretta [24] Ǒ, NiFe .,, ,NiFe,Ni, Ni,Ni;S, ǑFe-SNi-S.Fe-SNi-S, , SFe,Ni. IFeNi, NiFe.II ǑǑ,Ni. INi ,, . Ǒ, FeNiNi.II . , .II ,ǑII,, . ,,, , ,. 5 I,, 11455 ,.,Ǒ . IIMoIrRuǑ, .CAI ,,Ǒ. , NWA 2140Ǒ, I,,,I W.,,,. II.I Ǒ.,, ,. [1]Scott E R D. Elements, 2011, 7 47 [2]Grossman L. AREPS, 1980, 8 559 [3]MacPherson G J. Calcium-Aluminum-rich Inclusions in Chondritic Meteorites // Davis A M. Mete- orites, Comets, and Planets. Amsterdam Elsevier, 2003 201-241 [4]Palme H, Wlotzka F. EPSL, 1976, 33 45 [5] Bischoff A, Palme H. GeCoA, 1987, 51 2733 [6]Armstrong J T, El Goresy A, Wasserburg G J. GeCoA, 1985, 49 1001 [7]Berg T, Maul J, Schonhense G, et al. ApJ, 2009, 702 L172 [8]McMahon B M, Haggerty S E. LPSC, 1980, 11 1003 [9]Blum J D, Wasserburg G J, Hutcheon I D, et al. GeCoA, 1989, 53 543 [10]Palme H, Hutcheon I D, Spettel B. GeCoA, 1994, 58 495 [11]Campbell A J, Simon S B, Humayun M, et al. GeCoA, 2003, 67 3119 [12],,., 2009, 21 234 [13],,., 2005, 17 45 [14]Brearley A J, Jones R H. 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Science, 1997, 277 358 2115 The Petrology and Mineralogy Analysis of Noble Metal Alloys in the Inclusions of Chondrite An Implication on the Evolution of the Solar Nebula WU Yun-hua1,2XING Wei-fan1XU Wei-biao2,3 1 Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074 2 Key Laboratory of Planetary Sciences, Chinese Academy of Sciences, Nanjing 210008 3 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 ABSTRACT The Ca, Al-rich Inclusions CAIs in chondrites are believed to be the fi rst solids to have ed in the solar system which retain the original ination of the early solar nebula. However, in-depth researches reveal that most inclusions had experienced a complex history involving partial melting and secondary alteration. Studies on astrochem- istry are focused on refractory and chemically stable noble metal alloys in the CAI of a CV meteorite NWA 2140. The petrology and mineralogy of the alloys are analyzed. The com- positional data analysis of the component can imply the thermal history of the CAI. Two kinds of noble metal alloys are identifi ed, the primary condensates and secondary alteration products of pre-existing metals, respectively. Key words astrochemistry, meteorites, solid state refractory, s data analysis