Testing Models for Magma Transfer and Emplacement In 4-Dimensions:The Bergell Intrusion, N. Italy

4 维岩浆转移和侵位测试模型：意大利北部贝尔格尔侵入岩

• 批准号: 1219766
• 负责人: Blair Schoene
• 金额: $ 29.73万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-15 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1219766&HistoricalAwards=false
• 关键词: Testing; Models; Magma; Transfer; Emplacement

Intellectual Merit. The timescales and volumes of magma generation, transport, and emplacement help set the thermal, structural, and geochemical architecture of the lithosphere. Structural and petrologic data, in conjunction with recent advances in high-precision geochronology have led to contrasting models that involve either large volumes of magma transported and emplaced over short timescales or small batches of magma that are emplaced incrementally over many millions of years. Modelling of magma emplacement is hampered by : a) limited exposure of complete plutonic systems, and b) incomplete understanding of timescales timescales for magma emplacement. This proposal outlines a three year project targeting both challenges in the ca. 30 Ma Bergell intrusion, located in the Central Alps in N. Italy. This pluton was chosen for the following reasons: [1] extraordinary exposure and relief in the high Alps, [2] its young age permits very high-precision geochronology (ca. ±10-20 ka on single zircon fragments), [3] it exhibits a range in lithologies from gabbroic to granodioritic with archetypal normal zoning, and [4] an ~12-15 vertical km crustal cross section has been exposed through post-emplacement Alpine uplift and tilting. Based primarily on structural and field data, emplacement of the Bergell pluton is inferred to have been prolonged (ca. 5 Ma) with mid-crustal magma residence followed by diapirism/ballooning into the upper crust. This model is in stark contrast to recent incremental intrusion models for middle and upper crustal plutons and demands corroborating geochronology of samples with well-characterized field relations. The goal of this study is to construct a robust 4D model for pluton construction based on detailed field work and high-precision geochronology of carefully selected samples spanning the feeder zone to the roof. Initial work described in this proposal summarizes field work in the Bergell and presents a novel analytical approach combining zircon geochronology with in situ and bulk mineral trace element analyses on dated zircon fragments. Accessory mineral geochemistry will aid interpretations of high-precision geochronology by identifying xeno- and antecrysts and be used to detail potential magmatic differentiation trends, which place timescales on AFC processes and evaluate the degree to which magmatic intrusions remained closed systems. Integration of whole-rock major/trace element data will be used to decipher the size and frequency of magma pulses. Finally, this information will be used to develop numerical models of magma emplacement and evolution, and its implications for rheological characteristics of middle and upper crust. Broader Impacts. This work will train one PhD student (Kyle Samperton) and at least two senior Under graduates (Christine Chen ?13 in year 1) in a diverse set of tools including field geology, structural geology, and igneous petrology, and to supplement these skills with experience using cutting edge geochemical and isotopic analytical methods. This work involves training in one other laboratory (Prof. John Cottle?s LA-ICPMS lab at Univ. California Santa Barbara) and also in numerical techniques through collaboration with Dr. Catherine Annen (Univ. Bristol). The project will provide support for newly established analytical facilities at Princeton as well as the PI?s participation in the NSF-supported EARTHTIME initiative. The project links with a multi-university Swiss initiative to study the Adamello batholith, located ~100 km SE of the proposed field locale. The Adamello batholith is a classic locality for studies of magmatic processes but, significantly, lacks the vertical resolution through the crust provided by the Bergell intrusion. The PI has served as an external expert for that project and will organize a joint field symposia involving swiss PhD students and collaborators in summer 2013 in order to share the results of both projects.

智力优点。岩浆产生，运输和迁移的时间标准和体积有助于设定岩石圈的热，结构和地球化学结构。结构和岩石学数据以及最新的高精度年代学进展，导致了对比模型，这些模型涉及大量岩浆在短时间内运输和扩张的岩浆或在数百万年内逐渐增长的一小部分岩浆。岩浆的建模受到以下方式阻碍：a）完全pluton子系统的暴露量，b）对岩浆安置的时间标准时间尺度不完全理解。该提案概述了一个针对CA的两个挑战的三年项目。 30 Ma Bergell入侵，位于意大利北部的中央阿尔卑斯山。由于以下原因选择了这种plut子：[1]高阿尔卑斯山的非凡暴露和缓解，[2]其年轻时代允许非常高精度的年代学（在单个锆石碎片上大约10-20 ka），[3]它在岩性到Granodioritic crolttior and crosse crosse crosse cross and crossy and and and and and and and and s and and and and and and and and and and and and and and and and and [4]通过就业后高山隆起和倾斜而暴露了。主要基于结构和野外数据，推断出伯格尔pluton的驻留延长（大约5 mA），并具有中壳岩浆居住地，然后是二孔/气球进入上皮。该模型与最新的中地壳岩石的最新增量入侵模型形成鲜明对比，并要求佐证具有特征性场关系的样品的年代学。这项研究的目的是基于详细的现场工作和跨越Feer区域的精心选择的样品的高精度测量学构建强大的4D模型。该提案中描述的初始工作总结了Bergell中的现场工作，并提出了一种新型的分析方法，该方法将锆石的年代学与原位和散装矿物痕量元素分析在过去的锆石片段上进行了分析。辅助矿物地球化学将通过识别异晶和抗晶体来帮助解释高精度地年代学，并用于详细介绍潜在的岩浆分化趋势，这些趋势将时间表放置在AFC过程上，并评估岩浆入侵的程度。全摇滚主要/痕量元素数据的集成将用于破译岩浆脉冲的大小和频率。最后，这些信息将用于开发岩浆迁移和进化的数值模型及其对中壳和上皮流变特征的影响。更广泛的影响。这项工作将培训一名博士学位学生（Kyle Samperton）和至少两名高级本科生（Christine Chen？13年级的Christine Chen？13），其中包括一套潜水员的工具，包括现场地质学，结构地质学和火成岩岩石学，并使用最先进的地质和同位素分析方法来补充这些技能。这项工作涉及在另一个实验室进行培训（约翰·科特尔教授在加利福尼亚州圣塔芭芭拉大学的La-icpms实验室），以及通过与凯瑟琳·安娜（Catherine Annen）博士（布里斯托尔大学）合作而获得数值技术。该项目将为普林斯顿新建立的分析设施以及PI参与NSF支持的Earthtime倡议提供支持。该项目与瑞士多元大学的倡议联系起来，研究了拟议的现场场地约100公里的Adamello Batholith。 Adamello Batholith是研究岩浆过程的经典地点，但很重要的是，通过伯格尔入侵提供的外壳缺乏垂直分辨率。 PI曾是该项目的外部专家，并将在2013年夏季组织一次联合现场研讨会，涉及瑞士博士学位学生和合作者，以分享这两个项目的结果。