Collaborative Research: Sourcing A-type Granites in Ancient Rifts

9316144霍根南俄克拉荷马州奥拉克根的威奇托花岗岩是侵入大陆裂谷的A型花岗岩的经典例证，代表着发展对花岗岩来源的新见解的机会。关于威奇托花岗岩的有限的新的化学和同位素数据表明，与大多数以前提出的模型相反，玄武岩是通过晶体分馏而来的，地壳参与的程度很小。从这一重要的A型花岗岩群中选取花岗岩进行化学和同位素的联合研究，可以成功地确定地壳裂谷中A型花岗岩的成因和过程。威奇托花岗岩已经被细分为三个化学群。对代表这三个化学群的选定花岗岩片进行的结构、矿物学和化学研究将澄清这些岩套。将地球化学数据与同位素数据结合起来，将使我们能够看透分馏效应，以便确定来源。锆石和钛铁矿的地质年代学研究应该确定结晶年龄和潜在的来源年龄。如果要了解A型花岗岩的来源，就需要在一个受良好约束的构造环境中进行这样的研究。

9316144 Hogan The Wichita granites of the Southern Oklahoma Aulacogen, a classic illustration of A-type granites intruded in a continental rift, represent an opportunity to develop new insights into granite sourcing. Limited, new chemical and isotopic data on the Wichita granites suggest derivation by crystal fractionation of basalt with minor crustal involvement contrary to most previously proposed models. A combined chemical and isotopic study of selected granites from this important group of A-type granites can successfully identify sources and processes involved in A- type granite petrogenesis in crustal rifts. The Wichita Granites have already been subdivided into three chemical groups. Textural, mineralogic, and chemical studies of selected granite sheets, representing the three chemical groups, will clarify these suites. Combining geochemical data with isotopic data will allow us to see through fractionation effects in order to characterize sources. Geochronological studies of zircon and titanite should define crystallization ages and potentially source ages. Such a study is required in a well constrained tectonic setting if the source of A-type granites is to be understood.