Collaborative Research: Dating Submerged Continental Crust Beneath the Southern Gulf of California, and a Synthesis of the Magmatic and Tectonic History of This MARGINS Focus Site

合作研究：南加州湾下水下大陆地壳的年代测定，以及该边缘焦点地点的岩浆和构造历史的综合

• 批准号: 1144558
• 负责人: Peter Lonsdale
• 金额: $ 6.31万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-15 至 2014-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144558&HistoricalAwards=false
• 关键词: Collaborative; Research; Dating; Submerged; Continental

The PIs propose to measure and interpret U-Pb crystallization ages of a varied suite of volcanic and plutonic rocks recovered from water depths of 300-3500m at several hundred sites on the submerged and previously unsampled rifted continental crust that underlies most of the southern Gulf of California. Many samples were collected along traverses up fault scarps and across volcanic features by a remotely operated vehicle; 50 dredge hauls also recovered igneous rock. All relevant samples have been petrographically described and geochemically analyzed. These samples record a long and complex magmatic history in this region, which in the past 20 Myr has changed from a volcanic arc to a subaerial intra-continental rift, been flooded by a marine incursion, and developed a chain of axial basins growing by seafloor spreading. Radiometric dates are needed to define this history, and to test hypotheses that up till now have been solely derived from still-subaerial outcrops at the margins of the rift. Existing dating show striking discordance between the age estimates, hinting at interesting cooling histories with likely tectonic implications. Targeted zircon (U-Th)/He and K-feldspar 40Ar/39Ar thermochronologic analyses and modeling will constrain thermal histories, thereby contributing to understanding rift tectonics including continental uplift and subsidence in the gulf rift.The work will very likely deepen our understanding of rifting history of the southern Gulf of California. Funding will also provide research opportunities for graduate students, foster collaboration with Mexican scientists and the results will be used in ongoing education and outreach programs, such as SDSU's K-8 project.

PI建议测量和解释一套不同的火山岩和深成岩的U-Pb结晶年龄，这些岩石是从位于加州南部大部分地区下面的淹没和以前未取样的裂谷大陆地壳上的数百个地点的300- 3500米水深中回收的。许多样品是由遥控潜水器沿着沿着断层陡坎和火山特征采集的; 50次挖泥船也回收了火成岩。对所有相关样品进行了岩相学描述和地球化学分析。这些样品记录了该地区漫长而复杂的岩浆历史，在过去的2000万年里，该地区已从火山弧变为陆上陆内裂谷，被海洋入侵淹没，并发展了一系列因海底扩张而生长的轴向盆地。需要放射性测定年代来确定这段历史，并检验迄今为止仅从裂谷边缘的地表露头得出的假设。现有的年代测定显示，年龄估计之间存在着惊人的不一致，暗示着有趣的冷却历史，可能具有构造意义。锆石U-Th/He和钾长石40 Ar/39 Ar热年代学分析和模拟将制约热历史，从而有助于理解裂谷构造，包括大陆隆升和沉降，很可能加深我们对加州湾南部裂谷历史的认识。资金还将为研究生提供研究机会，促进与墨西哥科学家的合作，其结果将用于正在进行的教育和推广计划，如SDSU的K-8项目。