CAREER: Investigating Controls on Arc Flare-ups and the Growth of Lower Continental Crust

职业：研究电弧爆发和下大陆地​​壳生长的控制

• 批准号: 1352021
• 负责人: Joshua Schwartz
• 金额: $ 46.74万
• 依托单位: The University Corporation, Northridge
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-15 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1352021&HistoricalAwards=false
• 关键词: CAREER; Investigating; Controls; Arc; Flare

The proposed research program focuses on investigating the magmatic and thermal evolution of an exhumed, Cretaceous magmatic arc in Fiordland, New Zealand with the primary goal of determining the tempo and mechanisms of magmatic construction of lower arc crust. Geochronologic and geochemical data will be used to test three hypotheses: 1) magmatic fluxes into the lower and middle crust were episodic, spatially transient, and culminated in a brief, approximately 3 million year high flux event; 2) deep-crustal magmas were derived from both mantle wedge and pre-existing crustal sources and generated voluminous high-pressure eclogitic cumulates; and 3) the arc root experienced heterogeneous heating and cooling that is not easily explained by simple monotonic cooling models, but instead may be compatible with mafic underplating driven by asthenospheric upwelling beneath the lithospheric arc root. Addressing these hypotheses will be used to evaluate processes of arc root construction and modification, and to create a 4-dimensional petrologic model for the Cretaceous Fiordland arc. Magmatic arcs are the subduction factories on earth where large volumes of intermediate, or andesitic, continental crust are created. A fundamental problem in Earth sciences is that the dominant magmas generated from partial melting of the mantle in arc environments are silica poor basalts, rather than intermediate andesites. It has long been speculated that the evolution of mantle-derived magmas from basalt to andesite likely occurs in the deepest roots (25-60 kilometers depth) of arcs where fundamental processes such as fractional crystallization of dense minerals, magma mixing and assimilation of preexisting crust occur. Recently, high-precision isotopic dating of arc rocks has led to the idea that large volumes of magmas may be generated during flare-up events, characterized by intense periods of arc activity. These ideas suggest that continental crustal construction in magmatic arcs may be highly episodic and that much of the geochemical diversification of magmas that we see in modern arcs may occur during brief time periods within the roots of the magmatic arc. This project focuses on a unique, exhumed deep-crustal section of a continental arc in Fiordland, New Zealand where the deep crust is well exposed to 25-65 kilometers paleodepth. Preliminary data suggests that over 70% of the arc root was emplaced during a brief, high-flux event, and this project will allow the evaluation of the temporal and geochemical processes of continental crust construction in the deep roots of this magmatic arc.In addition to the scientific goals of the project, it also emphasizes the integration of research with a dynamic teaching and mentoring program that aims to disseminate knowledge at all academic levels from K-12 to graduate education. California State University Northridge (CSUN) undergraduate students will participate in field and laboratory research in the United States and New Zealand. Latino minority and female students (both underrepresented groups in the geosciences and STEM) will be recruited and mentored through the 'ROCs' outreach program (Research Opportunities for CSUN students). The 'ROCs' program is aimed at early involvement and mentoring of underrepresented undergraduate CSUN students in research projects and providing guidance on graduate and geosciences career paths through workshops and weekly meetings. The PI and CSUN students will also work with the Deep Cove Outdoor Educational Trust in Fiordland National Park (a UNESCO World Heritage site) to create hands-on, geoscience activities for K-12 students from across the South Island of New Zealand. Activities and short videos highlighting unique aspects of Fiordland geology will be available on a CSUN-hosted website, YouTube and Vimeo for broad dissemination to the public.

拟议的研究计划侧重于调查新西兰峡湾白垩纪岩浆弧的岩浆和热演化，主要目标是确定下弧地壳岩浆构造的速度和机制。地质年代学和地球化学数据将用于检验三个假设：1）进入下地壳和中地壳的岩浆通量是间歇性的、空间上短暂的，并在一次短暂的、大约300万年的高通量事件中达到顶峰； 2）地壳深部岩浆来源于地幔楔和先存地壳源，生成大量高压榴辉岩堆积物； 3）弧根经历了非均质加热和冷却，这不容易用简单的单调冷却模型来解释，但可能与岩石圈弧根下方的软流圈上涌驱动的镁铁质底侵兼容。解决这些假设将用于评估弧根构造和修改的过程，并为白垩纪峡湾弧创建 4 维岩石学模型。岩浆弧是地球上的俯冲工厂，在这里产生了大量的中间或安山大陆地壳。地球科学的一个基本问题是，弧环境中地幔部分熔化产生的主要岩浆是贫硅玄武岩，而不是中间安山岩。长期以来，人们推测，地幔岩浆从玄武岩到安山岩的演化可能发生在弧的最深根部（25-60公里深），其中发生致密矿物的分异结晶、岩浆混合和先存地壳同化等基本过程。发生。最近，对弧岩的高精度同位素测年得出了这样的想法：在以弧活动剧烈时期为特征的爆发事件中可能会产生大量岩浆。这些想法表明，岩浆弧中的大陆地壳构造可能是高度间歇性的，我们在现代弧中看到的岩浆地球化学多样化可能发生在岩浆弧根部的短暂时期内。该项目的重点是新西兰峡湾大陆弧上一个独特的、挖出的深地壳部分，该区域的深地壳充分暴露于 25-65 公里的古深度。初步数据表明，超过 70% 的弧根是在一次短暂的高通量事件期间就位的，该项目将能够评估该岩浆弧深部大陆地壳构造的时间和地球化学过程。为了实现该项目的科学目标，它还强调将研究与动态教学和指导计划相结合，旨在传播从 K-12 到研究生教育的所有学术级别的知识。加州州立大学北岭分校（CSUN）本科生将参加美国和新西兰的实地和实验室研究。将通过“ROC”外展计划（CSUN 学生的研究机会）招募和指导拉丁裔少数族裔和女学生（在地球科学和 STEM 领域都是代表性不足的群体）。 “ROC”计划旨在让代表性不足的 CSUN 本科生尽早参与和指导研究项目，并通过研讨会和每周会议为研究生和地球科学职业道路提供指导。 PI 和 CSUN 学生还将与峡湾国家公园（联合国教科文组织世界遗产）的 Deep Cove Outdoor Educational Trust 合作，为新西兰南岛各地的 K-12 学生举办实践地球科学活动。突出峡湾地质独特方面的活动和短视频将在 CSUN 托管的网站、YouTube 和 Vimeo 上向公众广泛传播。

项目成果

The tempo of continental arc construction in the Mesozoic Median Batholith, Fiordland, New Zealand

新西兰峡湾中生代中位岩基大陆弧构造的节奏

• DOI: 10.1130/l610.1
• 发表时间: 2017-06-01
• 期刊: Lithosphere
• 影响因子: 2.4
• 作者: J. Schwartz;K. Klepeis;Joseph F. Sadorski;H. Stowell;A. Tulloch;M. Coble
• 通讯作者: M. Coble

Gneiss domes, vertical and horizontal mass transfer, and the initiation of extension in the hot lower-crustal root of a continental arc, Fiordland, New Zealand

新西兰峡湾的片麻岩穹顶、垂直和水平质量传递以及大陆弧下地壳热根部的伸展起始

• DOI: 10.1130/l490.1
• 发表时间: 2016-03
• 期刊: Lithosphere
• 影响因子: 2.4
• 作者: Klepeis, Keith A.;Schwartz, Joshua;Stowell, Harold;Tulloch, Andrew
• 通讯作者: Tulloch, Andrew

Thermochronology of extensional orogenic collapse in the deep crust of Zealandia

西兰迪亚深部地壳伸展造山塌陷的热年代学

• DOI: 10.1130/ges01232.1
• 发表时间: 2016-05
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: Schwartz, Joshua J.;Stowell, Harold H.;Klepeis, Keith A.;Tulloch, Andy J.;Kylander;Hacker, Bradley R.;Coble, Matthew A.
• 通讯作者: Coble, Matthew A.