麻豆淫院

Around 800 million years ago, during the Tonian period, the Yangtze Block in South China experienced significant tectonic activity, in which the ancient supercontinent Rodinia broke off from the area that is now South China. This created the Yangtze Block plate, which then collided with the China Ocean Plate, causing an area of subduction鈥攚here the oceanic plate slides under the lighter continental plate. This process is known to result in the creation of a string of volcanoes on the surface.

The result of the subduction between the Yangtze Block and the China Ocean plates was the Panxi-Hannan volcanic arc along the Yangtze Block's margin, which is a well-studied Tonian continental arc. But a new study, in the Journal of Geophysical Research: Solid Earth, reveals that this tectonic event may have resulted in a much wider region of volcanic activity at the time.

Previous studies revolving around the tectonic activity of the Yangtze Block plate had focused on arc systems at the continental margins, but had not explored the continental interior, which is difficult to study due to a thick blanket of rock. However, the researchers of the new study were able to delve deeper into the basement properties and evolution of the Sichuan Basin in the Yangtze Block with the help of seven deep boreholes penetrating 3.6鈥�6.5 km into the surface and aeromagnetic surveys, enabling them to map the deep subsurface rock types.

Their analysis revealed an iron-rich strip of rock, indicating the presence of a fossilized magmatic arc belt hidden beneath the Sichuan Basin. The borehole samples dated back to the Tonian period, likely somewhere between 820 and 770 million years ago. The belt went on for around 700 km (about 400 miles) and, surprisingly, extended inland at least 400鈥�900 km from the Yangtze block's northwestern edge.

It was previously understood that these magmatic arcs only existed in thinner strips along the margins of plates, but the study authors believe this arc may be an extension of the Panxi-Hannan arc along the Yangtze Block plate. This could be caused by flat-slab subduction鈥攁 subduction process where the lower plate moves much farther before sinking due to entering at a shallower angle.

The authors explain, "Our findings extend the circum鈥怸angtze Tonian continental arc system (e.g., Panxi-Hannan arc) into the Yangtze Block's interior and provide new insights into the Tonian tectonic鈥恗agmatic evolution in the area. Similar to the Panxi-Hannan arc, we suggest the magmatic arc beneath the central Sichuan Basin is also related to southeastward oceanic subduction."

The results of the study offer new insights into crustal mechanics and have the potential to influence future geological resource exploration. This newfound inland extension of magmatic arcs may also encourage the exploration of buried arc systems in other continents.

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