Petrogenesis of Triassic Intrusions, SW Maine: Forerunners of WMMS Igneous Activity

新南威尔士中生代非造山期岩浆活动 英格兰是一个存在时间长、岩石学上多样的岩浆岩 活动 三个主要的岩浆活动脉冲被识别：（1）一个 早三叠世阶段，（2）一个空间上有限的和庞大的 侏罗纪脉冲;（3）区域性广泛的白垩纪。 现代岩石学研究集中在两个后来 岩石成因的结论不同于简单的地壳 深熔作用到地壳同化和分步同化 结晶（AFC）的镁铁质，幔源岩浆。 在 相反，最早的活动阶段，三叠纪事件， 石油化学被忽视了。 仅在西南缅因州曝光， 活动主要由Mt.阿伽门蒂库斯复合体 （碱性正长岩到花岗岩）和Abbott Mountain岩群 （正长岩）。 利用现代石油化工技术， 地质年代学（阶段岩石学，主要，微量，稀土 元素地球化学、Sr、Pb和Nd同位素地球化学， 40 Ar/39 Ar同位素地质年代学）， 仔细描述这些入侵，并制定全面的 岩石成因溶液 初步结果表明 地壳深熔作用，而不是镁铁质岩浆的AFC是重要的 这些岩浆的成因 如果是这样，那么这个三叠纪岩浆 事件可能类似于侏罗纪后期的脉冲， 被认为是这项活动的先驱。 比较 所有中生代火成岩的岩石成因模型 事件应该增加我们对这一演变的理解， “非造山”岩浆作用，并提供更好的约束， 构造/热活动的性质是最终的 事业

Anorogeneic igneous activity during the Mesozoic in New England was a long-lived and petrologically varied magmatic event. Three major pulses of magmatism are recognized: (1) an early Triassic phase, (2) a spatially restricted and voluminous Jurassic pulse, and (3) a regionally extensive Cretaceous phase. Modern petrologic investigations have concentrated on two later phases; petrogenetic conclusions vary from simple crustal anatexis to combined crustal assimilation and fractional crystallization (AFC) of mafic, mantle-derived magmas. In contrast, the earliest phase of activity, the Triassic event, has been petrochemically ignored. Exposed only in SW Maine, this activity is primarily represented by the Mt. Agamenticus complex (alkaline syenite to granite) and the Abbott Mountain stock (syenite). Using modern petrochemical techniques and geochronology (phase petrology, major, trace, and rare earth element geochemistry, Sr, Pb, and Nd isotope geochemistry, and 40Ar/39Ar isotope geochronology) the proposed research will carefully characterize these intrusions and develop comprehensive petrogenetic solutions. Preliminary results suggest that crustal anatexis and not AFC of mafic magmas is important in the genesis of these plutons. If so, then this Triassic magmatic event may be similar to the later Jurassic pulse and can be considered the forerunner of that activity. Comparison of petrogenetic models developed for all of the Mesozoic igneous events should increase our understanding of the evolution of this 'anorogenic' magmatism and provide better constraints on the nature of the tectono/thermal activity that was is ultimate cause.