Collaborative Research: Investigation of a Late Jurassic Paired Magmatic Belt (Blue Mountains, NE Oregon): Evaluation of Magmatic Growth During Contractional Orogeny

合作研究：晚侏罗世成对岩浆带（俄勒冈州东北部蓝山）的调查：收缩造山运动期间岩浆生长的评估

• 批准号: 0911735
• 负责人: Kenneth Johnson
• 金额: $ 7.76万
• 依托单位: University of Houston - Downtown
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911735&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigation; Late; Jurassic

The main goal of this research project is to understand the origin of plutons and batholiths in the Blue Mountains province of northeastern Oregon with important chemical characteristics (low Sr/Y, Na, Al, Sr, and high Y, in contrast to high Sr/Y, Na, Al, Sr, and low Y). In addition, they will study the significance of crustal deformation events involving arc-arc and arc-continent collision. High and low Sr/Y plutons occupy large areas in ancient and modern orogenic belts, such as in the Appalachian Mountains, New Zealand, and the Sierra Nevada, yet considerable controversy exists regarding mechanisms of their generation, the tectonic settings in which they form, and their role in the evolution of continental crust through time. Previous models have proposed that partial melting of subducting oceanic crust or lower continental crust may generate high Sr/Y magmas. This project uses structural geology, geochronology, and igneous and metamorphic petrology to test these pre-existing models, and proposes a new model in which lateral tectonic collisions of island arcs played an important role in controlling the onset and distribution of high Sr/Y magmatism. This study, if successful, will provide new insights into the mechanisms of high and low Sr/Y magma generation, their spatial and temporal distribution in orogenic belts, and their relationship to mineralization in the Blue Mountains province. This study also has broader implications for understanding changes in the Mesozoic crustal structure of the Blue Mountains province through lateral tectonic collisions.The PIs their undergraduate and graduate students are conducting a multidisciplinary study to investigate the magmatic development of paired high and low Sr/Y plutons and batholiths. This study focuses on understanding the timing and geochemical characteristics of high and low Sr/Y magmatism, and its relationship to Late Jurassic contractional deformation and metamorphism. We propose a new model in which Late Jurassic orogensis occurred in response to collision (arc-arc) during a relatively brief time interval (159-157 Ma), and resulted in crustal thickening in the Baker terrane. This change in crustal structure led to the establishment of two coeval, yet spatially and geochemically distinct belts of Late Jurassic to Early Cretaceous high and low Sr/Y plutons and batholiths at 147-143 Ma. We focus our study on the Blue Mountains province, because it contains one of the best-exposed examples of paired high and low Sr/Y magmatic belts associated with Late Jurassic contractional deformation in the North American Cordillera. We test our model through integrated and detailed geologic and structural mapping, geochemical and isotope studies (Sr-Nd-O), and U-Pb and Sm-Nd radiometric dating. If we are correct in our interpretation of these magmatic belts, this study will represent a unique opportunity to study processes of high and low Sr/Y magma generation and the interplay between collisional tectonics, magmatism and metamorphism in a Phanerozoic convergent margin setting.

该研究项目的主要目的是了解俄勒冈州东北部蓝山省的岩石和浴石的起源，与高SR/Y，Na，Al，Sr和高Y相比，与高SR/Y，Na，Na，Na，Al，Al，Sr和Low Y）相比之下。 此外，他们将研究涉及ARC-ARC和弧形碰撞的地壳变形事件的重要性。高和低的Sr/y岩石在古代和现代造山带中占据了很大的区域，例如在阿巴拉契亚山脉，新西兰和内华达州内华达山脉，但在这一代机制，构造环境以及它们在跨时间中的大陆甲壳中的作用方面存在着极大的争议。先前的模型提出，俯冲或下大陆壳的部分熔化可能会产生高SR/Y岩浆。该项目使用结构地质学，年代学以及火成岩和变质岩石学来测试这些先前存在的模型，并提出了一个新模型，其中岛屿弧的横向构造碰撞在控制高SR/Y Magmatism的发作和分布中起着重要作用。如果成功的话，这项研究将提供有关高和低岩浆产生机制的新见解，它们在造山带中的空间和时间分布以及它们与蓝山省矿化的关系。这项研究对理解蓝山省的中生代地壳结构的变化也具有更广泛的影响，通过横向构造碰撞。他们的本科生和研究生正在进行一项多学科研究，以研究配对高和低sr/y pl/y plutons and Batholiths的岩浆发展。这项研究重点是理解高和低岩浆的时间和地球化学特征，及其与晚期侏罗纪收缩变形和变质的关系。我们提出了一个新模型，其中侏罗纪晚期在相对短时间的时间间隔（159-157 MA）中响应碰撞（ARC-ARC），并导致面包板地层中的地壳增厚。地壳结构的这种变化导致建立了两个同时，但在空间和地球化学上截然不同的侏罗纪腰带，在147-143 MA处建立了早白垩纪高和低sr/y plutons and Batholiths。我们将研究重点放在蓝山省，因为它包含了与晚期侏罗纪收缩变形相关的配对高和低sr/y岩浆带的最佳实例之一。我们通过综合和详细的地质和结构映射，地球化学和同位素研究（SR-ND-O）以及U-PB和SM-ND辐射测定测试我们的模型。如果我们对这些岩浆带的解释是正确的，那么这项研究将代表一个独特的机会，用于研究高和低岩浆产生的过程，以及在phanerozoic融合余量环境中碰撞构造，岩浆和变质的相互作用。