The geochemistry of Archaean plagioclase-rich granites as a marker of source enrichment and depth of melting
The geochemistry of Archaean plagioclase-rich granites as a marker of source enrichment and depth of melting
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DOI：
10.1017/s1755691009016132
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发表时间：
2009-03
影响因子：
1.2
通讯作者：
J. Moyen;D. Champion;R. H. Smithies
中科院分区：
文献类型：
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作者：
J. Moyen;D. Champion;R. H. Smithies
在地球化学图解中，花岗岩类定义了反映分异或熔融程度增加的“趋势”。单个样品在这种趋势中的位置虽然与平衡温度有关，但很难解释。另一方面，趋势在地球化学空间中的位置（而不是样品在趋势中的位置）携带着重要的遗传信息，因为它们反映了来源的性质（富集程度）和熔融深度。本文讨论了地球化学趋势的解释，以提取有关花岗岩类岩浆来源和熔融深度的信息。将这种方法应用于巴伯顿花岗岩-绿岩带（南非）和皮尔巴拉岩带（澳大利亚）的中晚世花岗岩类，揭示了两个特征。第一个是通常被称为“TTG”（英云闪长岩、奥长花岗岩和花岗闪长岩）的岩石群的多样性。这些似乎是由至少三个不同的子系列，一个来自深熔融的相对贫化的来源，第二次从浅熔融的贫化来源，和第三次从浅熔融的富集来源。第二个特征是两个地区花岗岩的时空分布和组合的对比。
ABSTRACT In geochemical diagrams, granitoids define ‘trends’ that reflect increasing differentiation or melting degree. The position of an individual sample in such a trend, whilst linked to the temperature of equilibration, is difficult to interpret. On the other hand, the positions of the trends within the geochemical space (and not the position of a sample within a trend) carry important genetic information, as they reflect the nature of the source (degree of enrichment) and the depth of melting. This paper discusses the interpretation of geochemical trends, to extract information relating to the sources of granitoid magmas and the depth of melting. %Applying this approach to mid-Archaean granitoids from both the Barberton granite–greenstone terrane (South Africa) and the Pilbara Craton (Australia) reveals two features. The first is the diversity of the group generally referred to as ‘TTGs’ (tonalites, trondhjemites and granodiorites). These appear to be composed of at least three distinct sub-series, one resulting from deep melting of relatively depleted sources, the second from shallower melting of depleted sources, and the third from shallow melting of enriched sources. The second feature is the contrast between the (spatial as well as temporal) distributions and associations of the granites in both cratons.