Petrogenesis of Archean Granitoids and Implications for the Chemical Evolution of Cratonic/Lithosphere

尽管对许多早-晚太古代（2.7-3.8 Ga）的地层进行了全面的野外、岩石学、同位素、地球化学和构造研究，但关于大陆地壳的起源和早期生长的一些相对基本的问题仍未得到解决。这些研究包括早期大陆生长的构造环境，帮助稳定太古宙大陆块的花岗岩岩浆的最终来源，以及演化中的太古宙大陆内部花岗岩岩浆活动与地幔中深层克拉通根（龙骨）稳定之间关系的本质。该提案寻求资金用于在多铁砧装置中进行高压实验，旨在限制太古宙花岗岩类的起源，并旨在深入了解地幔在其起源中所起的作用。前人的实验研究表明，1-3 GPa含水玄武岩的低熔融程度所产生的液体，其化学成分大致为太古宙斑长岩-闪长岩-花岗闪长岩套（TTG），太古宙高低品位地形中主要的花岗类岩石，但存在一些微小但可能显著的差异。晚太古代（2.6-2.9 Ga）加拿大地盾的苏尔韦勒省和奴隶省的花岗岩-绿岩地形（所谓的“sanukitoid suite”的成员）具有化学特征（如高Cr和Ni含量），这与变质玄武岩部分熔融的简单起源不一致，并且表明地幔谱系。然而，就大多数地球化学参数而言，TTG花岗岩类来自基性地壳的部分熔融，在成分上似乎与可能来自地幔的sanukitoid花岗岩类具有连续性。许多解释，将被实验验证，可以解释这些观察：(1)TTG熔体对地幔橄榄岩的同化，(2)太古代TTG的玄武岩来源比在1-3 GPa的玄武岩熔融实验中使用的起始材料含有更多的镁质，或者(3)以前被TTG熔体修饰的地幔部分熔融产生的sanukitoids。当然，可能性(1)和(3)涉及TTG熔体与橄榄岩地幔之间的密切化学相互作用，对次大陆地幔的化学演化具有潜在的深远影响。

RappEAR-0003638Despite comprehensive field, petrologic, isotopic, geochemical, and structural studies in a number of well-exposed early- to late-Archean terrains (2.7-3.8 Ga old), some relatively basic issues regarding the origin and early growth of the continental crust remain unresolved. These include the tectonic setting in which early continental growth took place, the ultimate source of the granitoid magmas that helped stabilize continental masses in the Archean, and the nature of the relationship between granitoid magmatism within the evolving Archean continents and the stabilization of deep cratonic roots (keels) in the underlying mantle. The proposal seeks funding to conduct high-pressure experiments in the multi-anvil apparatus aimed at constraining the origin of Archean granitoids, and designed to provide insight into the extent to which the mantle was involved in their origin. Previous experimental studies have shown that low degrees of melting of hydrous basalt at 1-3 GPa produces liquids with the general chemical composition of Archean tonalite-trondhjemite-granodiorite suites (TTG), the dominant granitoid rock in Archean high- and low-grade terrains, but with some minor but perhaps significant discrepancies. Late-Archean (2.6-2.9 Ga old) granite-greenstone terrains in the Superior and Slave Provinces of the Canadian Shield (members of the so-called "sanukitoid suite"), possess chemical characteristics (such as high Cr and Ni contents) that are inconsistent with a simple origin by partial melting of metabasalt, and that suggest a mantle lineage. Yet in terms of most geochemical parameters, TTG granitoids, derived from partial melting of mafic crust, appear to be compositionally continuous with presumably mantle-derived granitoids of the sanukitoid suite. A number of explanations, which will be tested experimentally, could account for these observations: (1) assimilation of mantle peridotite by TTG melts, (2) the basaltic source for Archean TTG was more magnesian than the starting materials used in the basalt melting experiments at1-3 GPa, or (3) sanukitoids result from partial melting of mantle that had been previously modified by TTG melts. Possibilities (1) and (3), of course, involve intimate chemical interaction between TTG melts and peridotitic mantle, with potentially profound implications for the chemical evolution of the sub-continental mantle.