Reduced, reused and recycled: Detrital zircons define a maximum age for the Eoarchean (ca. 3750-3780 Ma) Nuvvuagittuq Supracrustal Belt, Quebec (Canada)
Reduced, reused and recycled: Detrital zircons define a maximum age for the Eoarchean (ca. 3750-3780 Ma) Nuvvuagittuq Supracrustal Belt, Quebec (Canada)
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DOI：
10.1016/j.epsl.2012.11.054
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发表时间：
2013-01-15
影响因子：
5.3
通讯作者：
Mojzsis, Stephen J.
中科院分区：
文献类型：
--
作者：
Cates, Nicole L.;Ziegler, Karen;Mojzsis, Stephen J.
冥古宙（3850 Ma前）碎屑锆石记录的一个关键发现是，花岗岩和玄武质地壳的二分法在地球形成的大约1.6亿年内建立起来（Harrison，2009年）。了解这个原始地壳的起源和命运将大大增加我们对冥古宙地球动力学的了解。从Sm-147，Sm-146-Nd-143，Nd-142同位素数据报告，从不同的始新世的世界各地，包括Nuvvuagittuq表壳带（NSB）在北方魁北克。NSB的一些贫钙（富钙橄榄岩）斜长角闪岩和花岗岩类片麻岩保存的Nd-142/Nd-144低于块状硅酸盐地球（BSE）;这些也显示出与Sm-147/Nd-144的正相关性，O 'Neil等人（2008年，2012年）使用Sm-147/Nd-144来分配一个约1000 - 100000个。4400 Ma年龄。或者，在大约3800 Ma的NSB形成期间继承了组合物（Roth等人，2013; Guitreau等人，2013年）。为了解决这一矛盾，离子探针U-Pb年龄报告的碎屑锆石从NSB变质沉积物内相同的表壳继承，保持低Nd-142/Nd-144。最年轻的火成岩源碎屑锆石芯确定了NSB的最大年龄约为0.0001年。3780 Ma.这个年龄比Nd-142/Nd-144与Sm-147-Nd-143回归得到的年龄年轻约6亿年。因此，就像其他始新世化石的Nd-142/Nd-144比值一样，NSB的非BSE Nd-142/Nd-144值是从一个较老的组分继承而来的。(C)2012 Elsevier B. V.保留所有权利。
A key discovery from the Hadean (pre-3850 Ma) detrital zircon record has been that the dichotomy of granitic and basaltic crust was established within about 160 Myr of Earth's formation (Harrison, 2009). Understanding the origin and fate of this primordial crust would greatly add to what we know about the geodynamics of the Hadean Earth. Insights emerge from Sm-147,Sm-146-Nd-143,Nd-142 isotope data reported from different Eoarchean terranes worldwide, including the Nuvvuagittuq Supracrustal Belt (NSB) in northern Quebec. Some Ca-poor (cummingtonite-rich) amphibolites and granitoid gneisses of the NSB preserve lower Nd-142/Nd-144 than Bulk Silicate Earth (BSE); these also show positive correlations against Sm-147/Nd-144 that were used by O'Neil et al. (2008, 2012) to assign a ca. 4400 Ma age. Alternatively, the compositions were inherited during the formation of the NSB at around 3800 Ma (Roth et al., 2013; Guitreau et al., 2013). To resolve this discrepancy, ion microprobe U-Pb ages are reported for detrital zircons from NSB meta-sediments from within the same supracrustal successions that preserve low Nd-142/Nd-144. The youngest detrital zircon cores of igneous derivation define a maximum age for the NSB of ca. 3780 Ma. This age is about 600 Myr younger than that obtained from Nd-142/Nd-144 vs. Sm-147-Nd-143 regressions. Thus, just like the variable Nd-142/Nd-144 ratios reported for other Eoarchean terranes, non-BSE Nd-142/Nd-144 values of the NSB were inherited from an older component. (C) 2012 Elsevier B.V. All rights reserved.