Radiogenic Isotopic Studies of Magmatism and Crust-Mantle Evolution

Patchett/Vervoort-0003343我们试图通过重新测定块状硅酸盐地球（BSE）Lu-Hf和Sm-Nd参数来改进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。 这可能意味着一个非常重要的早期分化事件被记录下来，这样一个看不见的补充水库存在于地幔中，或者可能在早期的太阳系碰撞中丢失。这也可能表明Lu-Hf的参考文献是不正确的，或者BSE实际上由于其他原因而不同于BSE。 我们打算通过对一组陨石的仔细分析来检查Lu-Hf陨石参数。 同时进行Sm-Nd表征，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，以更好地限制176 Lu的衰变常数，采用新鲜的前寒武纪粗粒岩，以获得内部等时线，并比较年龄的那些从精确的U-Pb测年的斜锆石或锆石的镁铁质侵入体。 这些研究将极大地改善地球分异过程Lu-Hf同位素研究的概念框架。

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.