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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Noble gas composition of Indian carbonatites (Amba Dongar, Siriwasan): Implications on mantle source compositions and late-stage hydrothermal processes
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Noble gas composition of Indian carbonatites (Amba Dongar, Siriwasan): Implications on mantle source compositions and late-stage hydrothermal processes

机译：印度碳酸盐（Siriwasan Amba Dongar，Siriwasan的高贵气体组成：对地幔源组合物和晚期水热过程的影响

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Within a stepwise crushing study we determined the noble gas composition of several calcite separates, one aegirine and one pyrochlore-aegirine separate of the carbonatite ring dyke complex of Amba Dongar and carbonatite sill complex of Siriwasan, India. Both carbonatites are related to the waning stages of volcanic activity of the Deccan Igneous Province ca. 65 Ma ago. Major observations are a clear radiogenic He-4* and nucleogenic Ne-21* imprint related to in situ production from U and Th in mineral impurities, most likely minute apatite grains, or late incorporation of crustal fluids. However, in first crushing steps of most calcites from Amba Dongar a well-resolvable mantle neon signal is observed, with lowest air corrected mantle Ne-21/Ne-22-compositions equivalent to the Reunion hotspot mantle source. In case of the aegirine separate from Siriwasan we found a neon composition similar to the Loihi hotspot mantle source. This transition from a mantle plume signal in first crushing step to a more nucleogenic signature with progressive crushing indicates the presence of an external (crustal) or in situ nucleogenic component unrelated and superposed to the initial mantle neon component whose composition is best approximated by results of first crushing step(s). This contradicts previous models of a lithospheric mantle source of the carbonatitic magmas from Amba Dongar containing recycled crustal components which base on nucleogenic neon compositions. Instead, the mantle source of both investigated carbonatite complexes is related to a primitive mantle plume source that we tentatively ascribe to the postulated Deccan mantle plume. If, as is commonly suggested, the present location of the Deccan mantle plume source is below Reunion Island, the currently observed more nucleogenic neon isotopic composition of the Reunion hotspot might be obliterated by significant upper mantle contributions. In addition, compared with other carbonatite complexes worldwide a rather sign
机译：在逐步破碎的研究中，我们确定了几个方解石的惰性气体组成，一种AegiNe和一种冰林 - AegiNe的碳酸根环堤复合体与印度西里扬山的碳酸根环堤复合物分开。两种碳酸盐族都与Deccan Igneous Province Ca的火山活性的阶段有关。 65 ma前。主要观察是一种透明的辐射性HE-4 *和核原性NE-21 *，与矿物质杂质的U和TH有关，最有可能的微小磷灰石谷物或晚期结合地壳液。然而，在来自AMBA Dongar的大多数燃烧石的第一次破碎步骤中，观察到可溶性地幔氖信号，具有最低的空气校正的搭桥NE-21 / NE-22组合物，其等于Reunion Hotspot Mantle源。如果与Siriwasan分开的Aegiine，我们发现类似于Loihi Hotspot Mantle源的霓虹灯组合物。从第一碎屑步骤中的偶然羽毛信号转变为具有渐进式破碎的更高核原签名，表明存在外部（地壳）或原位核酸组分的不相关，并叠加到最初的伴氖组件，其组合物最佳地近似第一次破碎步骤。这与Amba Dongar含有核酸氖组合物基础的CAMA CONGAR的碳酸岩石岩浆岩石岩石源的先前模型相矛盾。相反，研究的碳酸盐石复合物的地幔源与原始的披风羽流源有关，即我们暂时递断到假设的Deccan Mantle羽流。如果通常建议，Deccan Mantle Plume源的当前位置低于Reunion Island，目前观察到的统一热点的更多核核酸氖同位素组成可能是通过显着的上部地幔贡献来消除的。此外，与全世界的其他碳酸石复合物相比相当符号

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