The combined Lu-Hf and Sm-Nd mineral-whole rock, and zircon U-Pb, REE and Hf isotope study of ultra high pressure rocks from the CCSD program

CCSD 项目对超高压岩石进行 Lu-Hf 和 Sm-Nd 矿物-全岩以及锆石 U-Pb、REE 和 Hf 同位素联合研究

基本信息

批准号：
21971348
负责人：
Professor Dr. Stefan Weyer, Ph.D.
金额：
--
依托单位：
Abteilung Petrologie und Geochemie
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2006
资助国家：
德国
起止时间：
2005-12-31 至 2010-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/21971348?language=en
关键词：
combined Lu Hf Sm Nd

项目摘要

Ultrahigh pressure (UHP) rocks from the Chinese Continental Scientific Drilling (CCSD) program were chosen to study the Sm-Nd and Lu-Hf isotope systems in combination with U-Pb LA-ICP-MS and SHRIMP dating of distinct zircon domains. First results show that the combined use of trace element and U-Th-Pb isotope compositions of zircon and PT information from their mineral inclusions, allow the linkage between U-Pb ages and metamorphic reactions. Inherited and metamorphic zircons were distinguished based on CL imaging, mineral inclusions, trace element contents and Hf isotope composition. Up to three phases of zircon growth or re-crystallisation can be identified in a single sample. The ages are interpreted to date the time of (1) prograde and (2) UHP metamorphism during Middle Triassic subduction, and (3) retrograde metamorphism during Late Triassic exhumation. Ongoing studies of the Hf isotope analyses of UHP zircon domains from different samples promise new insights in the understanding of the behaviour of the Lu-Hf system during UHP metamorphism. Preliminary Lu-Hf and Sm-Nd grt-cpx isochrones from CCSD and Dabie eclogites yield surprisingly uniform ages that are in average about 6-8 Myr younger than UHP zircons. The interpretation of these ages is yet not clear for us. A major focus of the applied period of the proposal will be the application of the different chronometers (U-Pb on zircons and Lu-Hf / Sm-Nd on garnet-cpx) on minerals from the same samples. These studies should clarify if the different chronometers applied to different rocks on various sections of the drill hole yield consistent results or date different events. They will thus (1) test the limitations and robustness of the analytical methods, (2) allow to distinguish between analytical and geological scatter, and (3) will contribute to a better understanding of the metamorphic evolution of the Sulu terrane.

选择了来自中国大陆科学钻井（CCSD）计划的超高压力（UHP）岩石，以研究SM-ND和LU-HF同位素系统与U-PB LA-ICP-MS结合使用，以及不同锆石域的虾类。首先结果表明，锆石和PT信息的痕量元素和U-TH-PB同位素组成的联合使用允许U-PB年龄与变质反应之间的联系。根据CL成像，矿物包含，痕量元素含量和HF同位素组成区分遗传和变质的锆石。可以在单个样本中鉴定出多达三个锆石生长或重结的阶段。迄今为止，年龄的年龄是（1）期间三叠纪俯冲期间的（1）UHP变质的时间，以及（3）在晚期三叠纪晚期挖掘过程中逆行变质。对来自不同样本的UHP锆石域的HF同位素分析的持续研究有望在UHP变质过程中了解LU-HF系统行为的新见解。来自CCSD和Dabie Eclogites的初步LU-HF和SM-ND GRT-CPX等速线产生出令人惊讶的均匀年龄，平均比UHP锆石年轻约6-8 Myr。这些年龄的解释对我们来说尚不清楚。该提案的应用周期的主要重点是将不同的天元计（锆石上的U-PB和石榴石-CPX上的lu-hf / sm-ND）应用于同一样品的矿物质上。这些研究应阐明是否在钻孔的各个部分上应用了不同的岩石，会产生一致的结果或日期不同的事件。因此，（1）测试分析方法的局限性和鲁棒性，（2）允许区分分析和地质散射，（3）将有助于更好地理解苏鲁地层的变质演化。