Igniting Continental Arcs; A Petrologic Study Of Mafic Rocks And Peridotites From The Coast Ridge Belt, Santa Lucia Mountains (California)

点燃大陆弧；

• 批准号: 0229470
• 负责人: Mihai Ducea
• 金额: $ 22.17万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229470&HistoricalAwards=false
• 关键词: Igniting; Continental; Arcs; Petrologic; Study

Ducea and Chesley EAR-0229470 There is strong evidence that major continental magmatic arcs are being built in episodic "flare-ups" separated by periods of magmatic quiescence, although the mechanisms responsible for the high magmatic fluxes are not resolved. Moreover, flare- up events appears to be fueled by a mafic input, thought to be largely derived from continental lithospheric mantle. This requires the existence of a mantle lithosphere an order of magnitude thicker than allowed by observations in mantle wedges and tectonic models. However, most of this evidence comes from subordinate mafic rocks found in shallow exposures of batholithic terranes. Either the voluminous mafic input to the arc lower crust is not (predominantly) from the lithospheric mantle during high magmatic fluxes, or if it is, we need to revise our thinking regarding the dynamics of subduction beneath continents and the ability of continental lids to episodically feed melt-fertile mass to the mantle wedge. These issues will be addressed in a petrologic study of mafic rocks from a mid-crustal arc exposure in the Big Sur area of the Santa Lucia Mountains, central coastal California. The basement rocks exposed there represent a tilted exposure of a magmatic arc representing paleo-depths ranging from 25 km to 10 km. At about 25 km beneath the arc there is a transition from large intrusions of tonalite to granodiorite composition separated by steeply dipping screens typical of the Sierra Nevada batholith to near horizontal, foliated gneissic rocks with numerous mafic intrusions. Mafic intrusions, now either amphibolites or granulites, are abundant at this level, where they stalled due to buoyancy reasons. Our mapping, petrographic, chemical and isotopic results will be used to resolve crustal vs. sub-crustal, and lithospheric vs. asthenospheric reservoirs involved in continental arc magmatism and provide new constraints for the mechanisms of generation of large batholiths.

Ducea和Chesley EAR-0229470有强有力的证据表明，主要的大陆岩浆弧是在岩浆静止时期分开的情节“爆炸”，尽管无法解析高岩浆磁通量的机制。此外，耀斑事件似乎是由镁铁质输入所助长的，该事件被认为主要源自大陆岩石圈地幔。这需要地幔岩石圈的存在比地幔楔和构造模型中的观测值允许的厚度要厚。但是，这些证据中的大多数来自在沐浴石底浅的浅水处发现的下属镁铁质岩石。在高岩浆通量期间，对下壳的大量镁铁质输入不是（主要是）来自岩石圈地幔的（主要是），或者，如果是，我们需要修改我们对大陆下俯冲动态的思考，以及大陆盖的能力以及在层次上添加材料质量质量的质量。这些问题将在一项岩石岩石中的岩石学研究中解决，该岩石岩石是在加利福尼亚州中部沿海圣卢西亚山区大型苏尔地区中期的弧形暴露中。在那里暴露的地下室岩石代表了岩浆弧的倾斜暴露，代表着25公里至10 km的古深度。在弧线下约25公里处，从大型侵入的音调侵入到花岗闪石组成的过渡，这些成分被典型的内华达山脉浴位典型的陡峭浸入的筛网到近乎水平的水平，叶状的片状片状岩石，并具有大量的镁铁质入侵。镁铁质的侵入物，现在是两栖石或颗粒石，在此级别上很丰富，由于浮力原因，它们停滞不前。我们的映射，岩石学，化学和同位素结果将用于解决涉及大陆弧岩岩岩的岩层和岩石圈与微量圈的岩石层与微量磷酸化的储层，并为产生大型浴的机制提供新的约束。