A Field Study of the Liquid Line of Descent of Hydrous Alkaline-rich Magmas at Elevated Pressures (0.5-1.0 GPa): The Dariv Alkaline Intrusive Complex

高压（0.5-1.0 GPa）含水碱性岩浆下降液线的现场研究：达里夫碱性侵入杂岩

• 批准号: 1322032
• 负责人: Oliver Jagoutz
• 金额: $ 30万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322032&HistoricalAwards=false
• 关键词: Field; Study; Liquid; Line; Descent

Understanding the origin of the highly diverse nature of felsic magmas, erupted as rhyolite or emplaced as large upper-crustal batholiths, is crucial to the investigation of the mechanisms that generate the silica-enriched continental crust. General consensus exists that strongly so-called peraluminous granites are derived, at least to some significant extent, from muscovite- and biotite-dehydration melting of metasedimentary protholiths. The origin of so-called meta-aluminous granites, however, is less certain. This project aims to investigate the hydrous liquid line of descent (LLD) of an alkaline magma and the relative roles of hydrous fractional crystallization versus partial melting in the formation of meta-aluminous alkaline granites through a field-based study. While alkaline granites are volumetrically less significant than calk-alkaline granites, their petrogenesis is of particular importance as they are often associated with economically significant mineralization. We will study a newly discovered exposures in the Dariv arc complex (Altai region of western Mongolia). The project will investigate a layered sequence ranging from phologopite-dominated ultramafic/mafic to intermediate (quartz-) monzonite and (quartz-) syenites rocks is spatially associated with large alkali-feldspar granite bodies. A similarly complete alkaline plutonic sequence has, to our knowledge, never been described in the geological literature before. In particular, the ultramafic rock assemblages exposed in Mongolia are currently only described as xenoliths from alkaline basaltic magmas. The complete exposures from ultramafic to felsic rocks provide an unrivaled opportunity to investigate crystal fractionation as a possible mechanism of alkali-feldspar granite formation.

理解长英质岩浆的高度多样性的起源，被爆发为流纹岩，或以大型上皮浴力石的形式爆发，对于研究产生二氧化硅富含大陆壳的机制至关重要。普遍的共识存在，至少在一定程度上得出了从棉虫和生物片含水岩含水液的融化，这是一种强烈所谓的植物花岗岩。然而，所谓的元铝制花岗岩的起源不太确定。该项目旨在通过一项基于现场的研究来研究碱性岩浆的下降（LLD）以及含水分数结晶的相对作用与部分融化。虽然碱花岗岩在体积上的意义不如Calk-Akaline花岗岩，但它们的石油发生尤其重要，因为它们通常与经济上显着的矿化相关。我们将研究达里夫弧综合体（西蒙古的阿尔泰地区）的新发现的暴露。该项目将研究一个分层的序列，从属于磷酸石的超镁铁质/镁铁质到中间（Quartz-）monzonite和（Quartz-）Syenite Rocks在空间上与大型碱性 - 菲尔德斯帕花岗岩体相关。据我们所知，同样完整的碱性冥王分序列在地质文献中从未描述过。特别是，目前在蒙古暴露的超镁铁质岩石组合仅被描述为碱玄武岩岩浆的异种石。从超镁铁质到长英质岩石的完整暴露提供了一个无与伦比的机会，以研究晶体分馏，作为碱花岗岩形成的可能机制。