Radiogenic Isotopic Studies of Magmatism and Crust-Mantle Evolution

岩浆作用与壳幔演化的放射性同位素研究

• 批准号: 0003343
• 负责人: P. Jonathan Patchett
• 金额: $ 21万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003343&HistoricalAwards=false
• 关键词: Radiogenic; Isotopic; Studies; Magmatism; Crust

Patchett/VervoortEAR-0003343 We seek to improve the framework for Lu-Hf isotopic studies by redetermination of the Bulk Silicate Earth (BSE) Lu-Hf and Sm-Nd parameters. At present, the array of mantle and crustal samples appears not to contain the BSE point. This may suggest that a very important early differentiation episode is recorded, such that an unseen complementary reservoir exists in the mantle, or was perhaps lost in early Solar System collisions. It may also suggest that the chondritic reference for Lu-Hf is incorrect, or that BSE really differs from chondrites for other reasons. We intend to check the Lu-Hf chondritic parameters by careful analysis of a suite of chondritic meteorites. Sm-Nd characterization will be performed simultaneously, with the goal of ensuring comparability between Lu-Hf and Sm-Nd systems. We will also undertake work to better constrain the decay constant of 176Lu, employing fresh Precambrian dolerites, to obtain internal isochrons and compare ages to those from precise U-Pb dating of baddeleyite or zircon in the mafic intrusions. These investigations should enormously improve the conceptual framework for Lu-Hf isotopic study of Earth differentiation processes.

我们试图通过重新测定大块硅酸盐土（BSE）的Lu-Hf和Sm-Nd参数来改善Lu-Hf同位素研究的框架。目前，地幔和地壳样品阵列似乎不包含BSE点。这可能表明记录了一个非常重要的早期分化事件，例如地幔中存在一个看不见的补充储层，或者可能在早期太阳系碰撞中丢失。这也可能表明，Lu-Hf的球粒参考是不正确的，或者疯牛病与球粒陨石的真正不同是由于其他原因。我们打算通过对一组球粒陨石的仔细分析来检查Lu-Hf的球粒参数。Sm-Nd表征将同时进行，目的是确保Lu-Hf和Sm-Nd系统之间的可比性。我们还将开展工作，更好地约束176Lu的衰变常数，利用新的前寒武纪白云岩，获得内部等时线，并将年龄与基性侵入岩中坏辉石或锆石的精确U-Pb定年进行比较。这些研究将极大地改进地球分异过程中Lu-Hf同位素研究的概念框架。