signature=e08f9700cea211b1df83d3382540ed71,Correlation of mid-Cretaceous granites with source terran...-优快云博客

研究揭示了白垩纪时期加拿大育空南部花岗岩的广泛地质化学和同位素特征，通过与不同来源和宿主岩石的对比，探讨了其源地起源。三种不同的花岗岩类型分别与大陆边缘俯冲带、Cache Creek和Stikine地带有关，东部皮克诺卡岩带显示出更复杂的关系。文章还发现，皮克诺卡岩带的花岗岩可能源自更东的相同或相似的 crustal 来源，而东部最东部分的演化特征与北美古陆相关。

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摘要：

This study presents a broad geochemical and isotopic synthesis of mid-Cretaceous granites in the southern Yukon as well as a comparative data set for granites sourced from, and hosted by, accreted terranes in the west through to ancient cratonic rocks in the east. We present data from a traverse perpendicular to the strike of the northern Canadian Cordillera allowing comparison with the growing body of such data derived from the host terranes. Trace elements, specifically the “subduction signature,” allow the discrimination of oceanic verses continental crustal sources. Comparison of isotopic ratios of Sr and, particularly, Nd with published data further refine the correlation of granites with their source terranes. Granites are initially divided based upon their host morphogeological belts, however, our study indicates that the source terranes transcend these traditional boundaries. For Intermontane Belt hosted granites three distinct sources can be identified: an isotopically primitive (Sri, 0.7050; ?NdT, 2.3 to?–1.2), subduction-related source probably associated with the mid-Cretaceous continental margin; an isotopically primitive (Sri, 0.7032 to 0.7035; ?NdT, 4.2 to 1.4), non-subduction-related source identified as the host Cache Creek terrane; and an isotopically slightly more evolved (Sri, 0.7094 to 0.7101; ?NdT, 4.5 to?–7.3), subduction-related source identified as the host Stikine terrane. Immediately east of the Teslin Tectonic Zone (TTZ), pericratonic Omineca granites (Sri, 0.7032 to 0.7076; ?NdT, 2.0 to?–5.4) do not correlate with their host terranes, but instead show marked similarities with granites immediately to the west of the TTZ suggesting that the same, or similar crustal sources extend further east in the subsurface than previously thought. In the eastern pericratonic Omineca Belt, there is a substantial jump to more evolved isotopic values (Sri, 0.7172 to 0.7354; ?NdT,?–16.6 to?–21.7) for granites that extend to the most easterly exposed plutons of the cratonic Omineca Belt. These more isotopically evolved granites correlate with isotopic values for the pericratonic Yukon–Tanana and Cassiar terranes, as well as cratonic North America.

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