学习资料
无球粒陨石、石铁陨石和铁陨石统称为分异陨石，它们是由球粒陨石经高温熔融分异和结晶的产物，代表了小行星内部不同层次的样品。这些小行星的内部结构与地球相似，分三层，中心为铁核（铁陨石），中间为石铁混合幔层（石铁陨石），外部是石质为主的壳层（无球粒石陨石）。
无球粒陨石　它的金属铁镍含量很低或不存在，结晶程度比球粒陨石高，主要由不同矿物和角状碎屑组成的角砾岩组成。矿物成分和结构很像地球上的超基性岩,晶体较大,这类陨石新坠落者有玻璃光泽的黑色熔壳。在矿物成分上，球粒陨石的斜长石主要是钙长石，而无球粒陨石主要为奥长石，橄榄石的含量也比球粒陨石低。依据化学成分，无球粒陨石可分为贫钙（含CaO为0～3％）和富钙(含CaO为5～25％)两类。贫钙类包括顽火辉石无球粒陨石（类型符号为Ae），紫苏辉石无球粒陨石(Ah)，橄榄石无球粒陨石(Ac)，橄辉无球粒陨石(Au)；富钙类包括钛辉无球粒陨石(Aa)，透辉橄榄无球粒陨石(Au)，紫苏钙长无球粒陨石(AhO),钙长辉长无球粒陨石(Aeu)。因无球粒陨石的矿物和化学成分与玄武岩相似，故又称为玄武质无球粒陨石。约占已知陨石的4％，外观上与玄武岩、橄榄岩和辉岩等含硅量低的地球火成岩相似。成分类似于地球上的镁铁质和超镁铁质岩石，更接近于辉石岩，其中最主要的矿物是辉石和斜长石。地球的岩浆曾形成基性岩和超基性岩，无球粒陨石也许是从和岩浆相似的熔融物质中结晶而成；也可能是从总体上具有球粒陨石组成的母体的熔融和分馏结晶中衍生而得。
按照矿物成分，无球粒陨石可分成下列各群︰
1：原始无球粒陨石(PAC群)（Acapulcoites）
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橄榄古铜陨铁(A)(Lodranites) (B)（Brachinites）
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(C)（Winonaites）
2：HED无球粒陨石：它们都被认为是来自小行星灶神星的地壳，期间的差异只在于来自不同地质历史的母岩石。占所有发现陨石的5%，并占无球粒陨石的60%。她们可能是经由如下的途径由灶神星来到地球;灶神星被撞击抛射出碎片，产生直径10公里或更小的V-型小行星碎片。无论抛出的是大的小行星，或成为小的碎片，其中一些小的小行星组成了灶神星族，其他的则进一步的散射至各处。而且需要多次的撞击，抛射出的岩石才能达到我们已知的V-型小行星数量。然后发生在这些接近地球天体上的较小型撞击，将她们击碎成陨石体大小的石块，其中一些在稍后抵达地球。根据宇宙射线暴露的测量，认为多数的HED陨石来自几次不同型态的撞击事件，并且在太空中经历600～7,300万年的时间才撞击到地球。
（1）古铜钙长无球粒陨石(Howardites)
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（2）钙长辉长陨石(Eucrites)
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（3）奥长古铜无球粒陨石(Diogenites)
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3：月球陨石
（1）火星陨石(又称SNC陨石)（2）辉玻无球粒陨石(Shergottites)
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（3）透辉橄无球粒陨石(Nakhlites)
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（4）纯橄无球粒陨石(Chassignites)
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4：其它无球粒陨石
（1）顽火无球粒陨石(Aubrites)（主要矿物成分是玩火辉石并含少量透辉石和贫钙无球粒陨石，常具角砾构造。
http://imgi101i120.360doc.com/DownloadImg/2017/08/1315/108312102_26.jpg?Expires=1621472646&OSSAccessKeyId=LTAIth6fJnBvI6ht&Signature=2hg+p2191BP5SQnWpUrkJPyh6/w=&domain=109 http://imgi101i120.360doc.com/DownloadImg/2017/08/1315/108312102_27.jpg?Expires=1621472646&OSSAccessKeyId=LTAIth6fJnBvI6ht&Signature=7BRnSFTd71Qu0HbsN6vLGhlf/og=&domain=109
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（2）钛辉无球粒陨石(Angrites)
http://imgi101i120.360doc.com/DownloadImg/2017/08/1315/108312102_30.jpg?Expires=1621472646&OSSAccessKeyId=LTAIth6fJnBvI6ht&Signature=BwsZbD10mBMSz0XMirtawJD0nBk=&domain=109
（3）橄辉无球粒陨石(Ureilites)
橄辉无球粒陨石是一类特殊的无球粒陨石，既具有高度分异的火成特征，又具有原始球粒陨石的特征。橄辉无球粒陨石为超基性的岩浆岩，既显示原始无球粒陨石，又显示分异无球粒陨石的一些特征，并认为是来自球粒陨石质母体的部分熔融，大多数典型的橄辉无球粒陨石具单矿碎屑岩的结构，复矿碎屑岩质橄辉无球粒陨石较少，其角砾岩碎片含单矿碎屑岩橄辉无球粒陨石的石屑碎屑及其它物质。橄辉无球粒陨石为原始和分异特征的混合物，其成因模式主要是超基性火成堆积岩或部分熔融的残余。
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