Plutonism Across the Tujunga-North American Terrane Boundary: A Middle to Upper Crustal View of Two Juxtaposed Magmatic Arcs

跨越图洪加-北美地体边界的岩体论：两个并列岩浆弧的中上地壳视图

• 批准号: 8904060
• 负责人: James Lawford Anderson
• 金额: $ 12.82万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1991-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8904060&HistoricalAwards=false
• 关键词: Plutonism; Across; Tujunga; North; American

Petrological studies in southern California have revealed middle to upper crustal portions of two juxtaposed Mesozoic magmatic arcs one being a native terrane of the Cordilleran orogen and the other "exotic" Tujunga or San Gabriel terrane. Crystallization thermobarometry of successively intruded and dated plutons and their thermal aureoles have provided "crustal nails" to track the variable depth history of orogenic crust in both terranes. Deep Mesozoic crust is now exposed at the surface by virtue of two contrasting tectonic settings - lower plates of extensional detachment faults in Tertiary metamorphic core complexes and upper plates of Mesozoic basement-cored thrust faults. The goal of this proposal is to document the nature of Mesozoic are development as a function of crustal depth across the terrane boundary and to utilize this information to constrain the accretionary history of this region of the Cordillera. This proposal outlines a petrological investigation of the plutons and host assemblages in both terranes. The approach is field based but includes petrologic, chemical, isotopic, and mineralogic studies to evaluate evolution of the plutonic suites from their inception at the source region to the condition of their ascent and emplacement. Work to suggests that the two terranes were accreted by mid-Cretaceous, if not by the middle Jurassic. Much of the apparent "exotic" nature of the Tujunga terrane stems from its partial derivation from the middle crust. Work to date has identified crustal sections that one resided at depths to 16 to 30 km. These middle crustal rocks exhibit several distinct characteristic differences from that at shallower crustal levels including the occurrence of Proterozoic anorthosite + charnockite and an abundance of Mesozoic plutons ranging from unusally calcic two-mica granitoids to a variety of intermediate igneous suites including diorite, quartz diorite, and tonalite.

加州南部的岩石学研究表明 两个并置中生代的中上地壳部分 岩浆弧之一是安第斯山脉的原生火山 造山带和其他“异国情调”的图洪加或圣加布里埃尔山。 结晶温压法研究 定年的岩体和它们的热晕提供了“地壳 nails”来追踪造山地壳的变深历史， 两个都是。 中生代的地壳现在暴露在地表 由于两种截然不同的构造环境-- 第三纪变质核伸展拆离断层 中生代基底核状逆冲断层杂岩和上板块 断层 本提案的目的是记录 中生代是地壳深度的函数， 并利用这些信息来约束 科迪勒拉山脉这一地区的加积史 这 提案概述了对侵入岩的岩石学调查， 在两个集群中的主机集合。 该方法基于实地 但包括岩石学、化学、同位素和矿物学 研究，以评估从他们的深成套演化 在源头区域的初始阶段， 和炮位。 研究表明，这两个受害者是 如果不是在中侏罗世的话，也是在中白垩世的时候增加的。 多 图洪加人明显的“异国情调”性质源于 它的一部分来源于中地壳。 迄今为止， 确定了地壳部分，其中一个居住在深度为16至 30公里 这些中地壳岩石表现出几种不同的 与地壳浅层的特征差异 包括元古宙斜长岩+紫苏花岗岩的产出 以及丰富的中生代岩体， 二云母花岗岩类到各种中间火成岩套 包括闪长岩、石英闪长岩和英云闪长岩。