Age of the Archean Talga-Talga Subgroup, Pilbara Block, Western Australia, and early evolution of the mantle: new SmNd isotopic evidence
Age of the Archean Talga-Talga Subgroup, Pilbara Block, Western Australia, and early evolution of the mantle: new SmNd isotopic evidence
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西澳大利亚皮尔巴拉地块太古宙 Talga-Talga 亚群的年龄和地幔的早期演化：新的 SmNd 同位素证据
DOI：
10.1016/0012-821x(87)90025-2
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发表时间：
1987
影响因子：
5.3
通讯作者：
C. Chauvel
中科院分区：
文献类型：
--
作者：
G. Gruau;B. Jahn;A. Glikson;R. Davy;A. Hickman;C. Chauvel
太古代科马提岩，高镁玄武岩和拉斑玄武岩从北星星玄武岩和阿达山玄武岩建造的塔尔加-塔尔加亚群，Warrawoona群，皮尔巴拉块，西澳大利亚州，定义了一个线性相关的正常143 Nd/144 Ndvs.147 Sm/144 Ndisochron图。测得的年龄为3712 ± 98 Ma，初始εNd（T）为+1.64 ± 0.40。3712 ± 98 Ma的年龄与区域地层层序和已有的年龄资料相一致，Sm单键Nd线性排列可解释为给出Talga-Talga亚群喷发年龄的等时线。另一种解释是，等时线代表了一条混合线，给出了该亚群的前火山作用年龄。地球化学和同位素数据的考虑表明，塔尔加-塔尔加亚群的真正喷发年龄可能接近3500 Ma左右。无论年龄解释如何，新的Nd同位素数据支持早太古代地幔中存在古老的LREE贫化储层，并进一步表明皮尔巴拉火山岩的源区具有同位素不均匀性，εNd（T）值至少为0至+4.0。
Archean komatiites, high-Mg basalts and tholeiites from the North Star Basalt and the Mount Ada Basalt formations of the Talga-Talga Subgroup, Warrawoona Group, Pilbara Block, Western Australia, define a linear correlation on the normal143Nd/144Ndvs.147Sm/144Ndisochron plot. The data give an age of 3712 ± 98 Ma and initialεNd(T)of +1.64 ± 0.40. The 3712 ± 98 Ma date is consistent with the regional stratigraphic sequence and available age data and the Smsingle bondNd linear array may be interpreted as an isochron giving the eruption age of the Talga-Talga Subgroup. An alternative interpretation is that the isochron represents a mixing line giving a pre-volcanism age for the Subgroup. Consideration of geochemical and isotopic data indicates that the true eruptive age of the Talga-Talga Subgroup is possibly closer to about 3500 Ma. Regardless of the age interpretation, the new Nd isotopic data support an existence of ancient LREE-depleted reservoirs in the early Archean mantle, and further suggest that source regions for the Pilbara volcanic rocks were isotopically heterogeneous, withεNd(T)values ranging from at least 0 to +4.0.