Supplementary Tables for "A ~700-km-long Fossil Tonian Magmatic Arc Belt Hidden within the Yangtze Block’s Interior, South China" submitted to JGR-Solid Earth

Fossil magmatic arcs preserve important archives of juvenile magmatism, crustal growth and differentiation, thereby aiding in our understanding of continental evolutionary histories. However, some ancient fossil arcs are situated in continental interiors, where they are buried beneath thick cover sequences, making their identification challenging. In this study, we present a dataset of deep boreholes, geochronology, geochemistry, and geophysics to investigate the basement properties and evolution of the Sichuan Basin in the Yangtze Block, South China. These results provide evidence for a large Tonian (ca. 820–770 Ma) magmatic arc belt hidden within the interior of the Yangtze Block. Seven deep boreholes (~3600–6500 m) penetrating into basin basement, together with geochronology and 3D seismic reflection profiles, show extensive Tonian (ca. 820–770 Ma) rhyolite/granites overlain by Ediacaran sediments. Aeromagnetic data reveal a NE-SW-trending, ~700-km-long high positive magnetic anomaly belt (PMAB) across the central Sichuan Basin, indicating the presence of (ultra-) mafic rocks in lower crust. Correspondingly, the Tonian felsic rocks drilled within PMAB range were likely sourced from a juvenile and thickened lower crust based on petrogenetic and geochemical studies. Thus, we interpret the PMAB as a record of mantle-derived melts input, followed by their evolution into granitic melts within the crust. This process was associated with a Tonian arc magmatic front that was once occurred in the Yangtze Block’s interior. Our finding broadens the range of the Tonian continental arc system in the region, reaching at least 400–900 km landward from block’s northwestern margin. Such a broad orogenic system played a vital role in continental evolution, element recycling, and basin formation of the Yangtze Block.

古火山弧（fossil magmatic arcs）是记录新生岩浆作用、地壳生长与分异过程的重要载体，助力我们深入解析大陆演化历史。然而，部分古老古火山弧位于大陆内部，被厚层覆盖层掩埋，极大增加了其识别难度。本研究构建了一套包含深钻孔、地质年代学、地球化学与地球物理数据的数据集，用以探究华南扬子地块（Yangtze Block）四川盆地的基底属性及其演化历程。本研究结果为扬子地块内部隐藏的大型拉伸纪（Tonian，约8.2亿~7.7亿年）火山弧带提供了实证依据。7个穿透盆地基底的深钻孔（孔深约3600~6500米）结合地质年代学数据与三维地震反射剖面结果显示，区内广泛分布拉伸纪（约8.2亿~7.7亿年）流纹岩/花岗岩，其上被埃迪卡拉纪（Ediacaran）沉积地层覆盖。航空磁测数据显示，四川盆地中部发育一条北东-南西走向、长约700千米的高正磁异常带（PMAB），指示下地壳中存在（超）镁铁质岩。相应地，基于岩石成因与地球化学研究，PMAB范围内钻孔揭露的拉伸纪长英质岩可能起源于新生且加厚的下地壳。因此，我们将PMAB解读为幔源熔体注入并在壳内演化形成花岗岩熔体的记录。该过程与曾发育于扬子地块内部的拉伸纪弧岩浆前锋带相关。本研究发现将该区域拉伸纪大陆弧系统的分布范围拓展至距地块西北缘至少400~900千米的陆内区域，这类大型造山系统对扬子地块的大陆演化、元素循环与盆地形成均具有关键作用。