Collaborative Research: Use and Abuse of Zircon Thermometry - Integrating Modeling, Trace Element Chemistry and Isotopes to Maximize the Use, Limit the Abuse

合作研究：锆石测温法的使用和滥用 - 整合建模、微量元素化学和同位素以最大限度地利用、限制滥用

• 批准号: 1447611
• 负责人: Scott Samson
• 金额: $ 13.9万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1447611&HistoricalAwards=false
• 关键词: Collaborative; Research; Use; Abuse; Zircon

Zircon (ZrSiO4) is arguably the single most powerful mineral for elucidating the evolution of the continental crust. The proposal will take advantage of the ability of zircon to record the temperature history of magma generated in the crust. We will specifically target granites produced in the period of earth history at approximately 1.05 billion years ago (the Grenville orogenic event). Our prior research demonstrated that this is a unique episode for generation of large volumes of exceptionally hot (900-1100 oC) granitic magma. The fingerprint of these hot granites includes high zirconium contents and conspicuously high modal abundance of zircon that does not contain xenocrysts of prior zircon (i.e., the zircon is not recycled from other crustal rocks and represents a primary chemical/mineralogic feature of the granites). Preliminary chemical analysis of the zircon in the hot granites demonstrates that the zircon also has high titanium contents, which prove high zircon crystallization temperatures. Computer modeling of the crystallization history of the high zirconium granites also demonstrates that zircon begins crystallization at ~1000 oC. The important insight from these preliminary results regarding the evolution of the Earth?s crust is that there must be unique lithospheric conditions in order to generate such hot granites. The proposed research will target for study a much larger suite of granites from the Grenville Blue Ridge Province in eastern North America (Shenandoah massif, Virginia) where we have identified a terrane-wide occurrence of high zirconium granites. The purpose of the research is to more thoroughly elucidate the temperature history of the Grenville granite suite and examine in detail the chemical and textural relationship of zircon to the bulk rock chemistry and modal mineralogy, in order to more precisely ascertain the conditions at which the zircon crystallized. We will conduct whole rock geochemical analysis, crystallization modeling using the program rhyoliteMELTS, cathodolomuninescence imaging of individual zircon grains to explore for potential xenocrysts, and ion microprobe analysis of trace elements and isotopes in zircon. The research will be conducted by graduate and undergraduate students from the collaborating institutions, providing critical training for future geoscientists.

锆石（ZRSIO4）可以说是阐明大陆壳演化的最强大的矿物。该提案将利用锆石记录地壳中产生的岩浆温度历史的能力。我们将特别针对大约10.5亿年前（格伦维尔造型事件）的地球历史时期生产的花岗岩。 我们先前的研究表明，这是一个独特的发作，用于产生大量异常热（900-1100 OC）花岗岩岩浆。 这些热花岗岩的指纹包括高锆石含量和明显的高模态丰度，不包含先前锆石的异种晶体（即，氧化锆并未从其他甲壳岩中再生，代表了花岗岩的主要化学/矿物质学特征）。 热花岗岩中锆石的初步化学分析表明，锆石还具有较高的钛含量，这证明了高锆石结晶温度。高锆花岗岩结晶历史的计算机建模还表明，锆石在〜1000 OC下开始结晶。这些关于地球演化的初步结果的重要见解是必须存在独特的岩石圈条件才能产生这种热的花岗岩。拟议的研究将针对从北美东部的格伦维尔蓝岭省（弗吉尼亚州的雪兰多·马西夫）研究一套更大的花岗岩套件，在那里我们已经确定了高锆花岗岩的范围内发生的。该研究的目的是更彻底地阐明格伦维尔花岗岩套件的温度历史，并详细检查锆石与块状岩石化学和模态矿物学的化学和纹理关系，以便更精确地确定锆石结晶的条件。我们将使用程序的浮力成分，单个锆石晶粒的阴极发光成像进行整体岩石地球化学分析，结晶建模，以探索潜在的异晶的探索以及对氧化锆中的微量元素和同位素的离子微探针分析。这项研究将由合作机构的研究生和本科生进行，为未来的地球科学家提供重要的培训。