Collaborative Research: The provenance of "Grenville" age detrital zircon in western North America and the Neoproterozoic to early Paleozoic evolution of southwestern Laurentia

合作研究：北美西部“格伦维尔”时代碎屑锆石的物源和劳伦西亚西南部新元古代至早古生代的演化

• 批准号: 1251869
• 负责人: Christopher Fedo
• 金额: $ 4万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-15 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1251869&HistoricalAwards=false
• 关键词: Collaborative; Research; provenance; Grenville; age

Collaborative Research: The provenance of "Grenville" age detrital zircon in western North America and the Neoproterozoic to early Paleozoic evolution of southwestern LaurentiaR. Lang Farmer, University of Colorado, EAR-1251851Christopher Fedo, University of Tennessee, EAR-1251869ABSTRACTDetrital zircon U-Pb age determinations have become a primary tool in siliciclastic sedimentary provenance studies due in part to the advent of rapid, in situ methods of obtaining isotopic data from individual zircon grains. However, the ability to collect such data is outstripping our understanding of the limitations of using U-Pb age spectra in interpreting continental tectonics and paleogeography. In this study, PIs are interested in assessing the significance, in terms of the sediment provenance, of variations in the age spread and relative peak height of specific detrital zircon age populations in siliciclastic sedimentary successions. Their approach is through combined in situ zircon U-Pb and Hf isotope analyses, data to be obtained using the laser ablation-multicollector ICPMS technique. PIs will target Mesoproterozoic to Cambrian sedimentary successions in the SW United States and northern Mexico, rocks that have been extensively used for U-Pb detrital zircon studies, but for which there is little detrital zircon Hf isotope data. Existing U-Pb age spectra reveal that a significant fraction of the detrital zircons in these rocks were derived from 1.0 Ga to 1.3 Ga ("Grenville") basement sources. The width and relative peak heights described by detrital zircon in this age range vary considerably both temporally and spatially within these sedimentary successions. Many samples are dominated by ~1.1 Ga detrital zircon, which on the basis of their U-Pb ages alone implies that these zircon were all derived from the same Mesoproterozoic basement source. However, PIs pilot Hf isotopic studies of "Grenville" detrital zircon show that the ~1.1 Ga grains vary by over 15 epsilonHf(0) units and reveal that these zircons do not all share the same provenance. This fact is not recognizable from the U-Pb age spectra alone. Based on this observation, it is suggested that combined U-Pb and Hf isotopic data can be used to explore how changes in the characteristics of the "Grenville" peaks in detrital zircon age spectra reflect changes in the ultimate bedrock source of these detrital grains. A better understanding of the basement provenance for Mesoproterozoic detrital zircons can, in turn, be used terms to refine models for the Precambrian to early Paleozoic tectonic and paleogeographic evolution of North America. PIs will conduct a broad survey of the U-Pb and Hf isotopic compositions of potential sources of "Grenville" zircon amongst 1.0 Ga to 1.3 Ga igneous rocks within the Grenville Orogen in the central and southern Appalachians, in the Llano Uplift in Texas, and among the ~1.1 Ga igneous rocks distributed throughout Paleoproterozoic crust of the SW U.S. and northern Mexico. They will apply this information, along with whole-rock Nd isotopic analyses on samples for which such data not already available, to assess the provenance of "Grenville" detrital zircon in siliciclastic sedimentary rocks in the Death Valley region and in the Caborca area of central Sonora (MX).

合作研究：北美西部“格伦维尔”年龄碎屑锆石的物源及西南劳伦蒂亚R. Lang Farmer，科罗拉多大学，1251851 Christopher Fedo，田纳西大学，1251869摘要碎屑锆石U-Pb年龄测定已成为硅质岩沉积物源研究的主要工具，部分原因是快速原位方法的出现，从单个锆石颗粒中获得同位素数据。 然而，收集这些数据的能力超出了我们对使用U-Pb年龄谱解释大陆构造和古地理的局限性的理解。 在这项研究中，PI感兴趣的是评估的意义，在沉积物的来源，在特定的碎屑锆石年龄人群的年龄分布和相对峰值高度的变化在silicicicon-depositing继承。 他们的方法是通过结合原位锆石U-Pb和Hf同位素分析，数据将使用激光烧蚀-多接收器ICPMS技术获得。 PI将针对美国西南部和北方墨西哥的中元古代至寒武纪沉积序列，这些岩石已被广泛用于U-Pb碎屑锆石研究，但碎屑锆石Hf同位素数据很少。 现有的U-Pb年龄谱表明，这些岩石中的碎屑锆石很大一部分来自1.0 Ga ~ 1.3 Ga（“格伦维尔”）基底源区。 该年龄段碎屑锆石的宽度和相对峰高在这些沉积序列中在时间和空间上变化很大。 许多样品以~ 1.1Ga碎屑锆石为主，单从其U-Pb年龄就可推断这些锆石均来自同一中元古代基底源区。 然而，PI先导Hf同位素研究的“格伦维尔”碎屑锆石表明，~1.1 Ga颗粒的变化超过15 epsilonHf（0）单位，并揭示这些锆石并不都共享相同的来源。 这一事实是不能单独从U-Pb年龄谱中识别的。 在此基础上，建议联合U-Pb和Hf同位素数据可以用来探讨如何在变化的“格伦维尔”峰在碎屑锆石年龄谱的特征的变化反映了这些碎屑颗粒的最终基岩来源的变化。 更好地了解中元古界碎屑锆石的基底来源，反过来，可以用来完善北美前寒武纪至早古生代构造和古地理演化模型。 PI将对阿巴拉契亚山脉中部和南部格伦维尔造山带内1.0 Ga至1.3 Ga火成岩中“格伦维尔”锆石潜在来源的U-Pb和Hf同位素组成进行广泛调查，这些火成岩位于德克萨斯州的拉诺乌托地区，以及分布在美国西南部和墨西哥北方古元古代地壳中的~1.1 Ga火成岩中。 他们将应用这些信息，沿着对尚未获得此类数据的样品进行全岩Nd同位素分析，以评估死亡谷地区和索诺拉中部（MX）卡博尔卡地区硅质沉积岩中“格伦维尔”碎屑锆石的来源。