EVIDENCE FOR CARBONATE IN THE MANTLE
EVIDENCE FOR CARBONATE IN THE MANTLE
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DOI：
10.1038/324050a0
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发表时间：
1986-11-06
期刊：
影响因子：
64.8
通讯作者：
BERG, GW
中科院分区：
文献类型：
--
作者：
BERG, GW
金伯利岩岩浆从地球表面深处约150公里处喷发出来，携带着罕见的碳元素——钻石，其中存在原生碳酸盐，这是地幔中存在碳储层的证据。关于这种碳储存形式的假设在很大程度上是推测性的，直到实验室实验1,2确立了在约50公里深处，碳可以与固体碳酸盐，白云岩（CaMg(CO3)2）和菱镁矿（MgCO3）结合在一起。然而，尽管对这些岩石进行了25年的深入研究，但在地幔岩石样本中只记录了一次微小的白云岩包裹体。在这里，我报告了迄今为止未被描述的水镁石/方解石共生体（Mg(OH)2/CaCO3）在南非金伯利含金刚石火山金伯利岩管中地幔源包体中的存在。这些相互生长可以反映地幔中存在相对丰富的白云岩。迄今为止，它们似乎一直被忽视，因为它们的质地很好，而且容易被次生蛇纹石取代。
The presence of primary carbonate in kimberlite magmas, which erupt tp the Earth's surface from depths of ≳150 km, carrying with them the rare elemental form of carbon, diamond, is evidence for a reservoir of carbon in the Earth's mantle. Hypotheses about the form in which this carbon is stored were largely speculative until laboratory experiments1,2established that at depths of ≳50 km carbon can be incorporated in the solid carbonates, dolomite (CaMg(CO3)2) and magnesite (MgCO3). However, only one instance of minute inclusions of dolomite in a sample of rock from the mantle has ever been recorded3, despite 25 years of intensive study of these rocks. Here I report the presence of hitherto undescribed brucite/calcite intergrowths (Mg(OH)2/CaCO3) in mantle-derived xenoliths which occur in the diamond-bearing volcanic kimberlite pipes of Kimberley, South Africa. These inter-growths could reflect the presence of relatively abundant dolomite in the mantle. They seem to have been overlooked to date because of their fine textures and susceptibility to replacement by secondary serpentine.