A primitive dark inclusion with radiation-damaged silicates in the Ningqiang carbonaceous chondrite

被引:23
作者
Zolensky, M [1 ]
Nakamura, K
Weisberg, MK
Prinz, M
Nakamura, T
Ohsumi, K
Saitow, A
Mukai, M
Gounelle, M
机构
[1] NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA
[2] CUNY, Kingsborough Coll, Dept Phys Sci, New York, NY 11235 USA
[3] Amer Museum Nat Hist, Dept Earth & Planetary Sci, New York, NY 10024 USA
[4] Kyushu Univ, Fac Sci, Fukuoka 8120053, Japan
[5] Inst Mat Struct Sci, KEK, High Energy Accelerator Res Org, Photon Factory, Tsukuba, Ibaraki 305, Japan
[6] Univ Paris 11, CSNSM, F-91405 Orsay, France
关键词
D O I
10.1111/j.1945-5100.2003.tb00266.x
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
A petrologic and TEM study of a remarkable dark inclusion (DI) in the Ningqiang CV3 chondrite reveals that it is a mixture of highly primitive solar nebula materials. The DI contains two lithologies. The first, lithology A, contains micron-sized olivine and pyroxene grains rimmed by amorphous materials with compositions similar to the underlying crystalline grains. The second, lithology B, appears to preserve the mineralogy of lithology A before formation of the amorphous rims. Overall, the Ningqiang DI appears to record the following processes: 1) formation (condensation and Fe-enrichment) of olivine crystals in the nebula with compositions of Fo(42-62); 2) irradiation, resulting in amorphitization of the olivine and pyroxene to varying degrees; 3) partial annealing, resulting in formation of fairly large, euhedral olivine and pyroxene grains with remnant amorphous sharply-bounded rims; 4) in some cases, prolonged annealing, resulting in the formation of microcrystalline olivine or pyroxene rims. The latter annealing would have been a natural consequence of irradiation near the critical temperature for olivine; and 5) mixture of the above materials (lithology A) with nebular condensate high-Ca pyroxene and olivine, which escaped nebular processing, to become lithology B. We suggest that the amorphous rims in lithology A formed in an energetic solar event such as a bi-polar outflow or FU-orionis flare.
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收藏
页码:305 / 322
页数:18
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