Pb isotopic domains from the Indian Ocean sector of Antarctica: implications for past Antarctica–India connections

New feldspar lead isotope compositions of crystalline rocks from the Indian Ocean sector of East Antarctica, in conjunction with the review of data from elsewhere within the continent and from continents formerly adjacent within Gondwana, refine boundaries and evolutionary histories of terranes previously inferred from geological mapping and complementary isotope studies. Coastal Archaean Vestfold and Napier complexes have overlapping compositions and had Pb isotopes homogenized at 2.5 Ga sourced from or within already fractionated protoliths with high and variable U–Pb. Identical compositions from the Dharwar Craton of India support a correlation with these Antarctic terranes. The Proterozoic–Palaeozoic Rayner Complex and Prydz Belt yield more radiogenic compositions and are broadly similar and strongly suggest these units correlate with parts of the Eastern Ghats Belt of India. A strikingly different signature is evident from the inboard Ruker Complex, which yielded unradiogenic compositions. This complex is unlike any unit within India or Australia, suggesting that these rocks represent exposures of an Antarctic (Crohn) Craton. Compositions from the enigmatic Rauer Terrane are consistent with a shared early history with the Ruker Complex but with a different post-Archaean evolution.

全新测得的东南极洲印度洋海域结晶岩长石铅同位素组成数据，结合对该大陆其他区域以及冈瓦纳古陆（Gondwana）昔日毗邻大陆的相关数据回顾梳理，优化了此前通过地质填图与配套同位素研究所推断的各地体（terrane）的边界与演化历史。沿海太古代（Archaean）韦斯特福尔（Vestfold）杂岩与内皮尔（Napier）杂岩的同位素组成相互重叠，且铅同位素在25亿年（2.5 Ga）时完成均一化，其物源来自或赋存于分异程度较高、铀-铅（U–Pb）比值高且变化显著的原岩。印度达尔瓦尔克拉通（Dharwar Craton）的同位素组成与上述南极地体完全一致，佐证了二者的亲缘关联。元古代（Proterozoic）-古生代（Palaeozoic）雷纳杂岩（Rayner Complex）与普里兹带（Prydz Belt）的同位素组成具有更强的放射成因特征，二者整体相似性极高，有力表明这些地质单元与印度东高止带（Eastern Ghats Belt）的部分区域存在亲缘关联。而内陆的鲁克尔杂岩（Ruker Complex）则呈现出截然不同的同位素特征，其组成未表现出放射成因富集。该杂岩与印度或澳大利亚境内的任何地质单元均不相同，表明其岩层出露于南极克罗恩克拉通（Crohn Craton）。神秘的劳厄地体（Rauer Terrane）的同位素组成与鲁克尔杂岩具有共同的早期演化历史，但太古宙后的演化路径存在显著差异。