Scientists Uncover a 400-Mile-Long Volcanic Legacy Beneath China's Surface
In a groundbreaking discovery, researchers have unearthed a colossal chain of extinct volcanoes hidden deep beneath southern China, offering a glimpse into Earth's ancient geological past. This remarkable arc of fossilized volcanoes, stretching over 400 miles, is estimated to be nearly 800 million years old and has been silently resting beneath the Sichuan Basin.
The team, led by scientists Zhidong Gu from PetroChina and Junyong Li from Nanjing University, utilized airborne magnetic surveys, akin to a geological X-ray, to detect a significant magnetic anomaly buried approximately 6 kilometers below the surface. This anomaly revealed a long, iron-rich rock belt spanning about 430 miles from northeast to southwest across the Yangtze Block.
The analysis of rock samples from deep boreholes further confirmed the presence of arc volcanism, a process where magma rises above a subducting oceanic plate. The rocks, dating back between 770 and 820 million years, align with the early Neoproterozoic era. What's astonishing is the volcanic arc's inland extension, typically found near continental margins, highlighting the unique nature of this discovery.
The researchers propose that flat-slab subduction, a horizontal tectonic movement, played a crucial role in the formation of this volcanic system. This process involves the oceanic plate gliding beneath the continent at a shallow angle before descending deeper, resulting in two parallel belts of volcanic activity, one near the boundary and another far inland.
However, geologist Peter Cawood from Monash University in Australia offers an alternative perspective, suggesting that the feature could represent two separate volcanic systems formed around the same time and later joined together. This interpretation adds complexity to the understanding of the volcanic arc's formation.
The timing of this volcanic belt coincides with significant geological and environmental changes, particularly in the global carbon cycle, between 720 million and 1 billion years ago. The release of carbon dioxide by volcanoes and the subsequent pull-out of carbon by mountain formation and weathering are key drivers of Earth's climate over geological time.
While the exact role of this Chinese volcanic system in the ancient carbon cycle remains uncertain, its immense scale and timing have sparked intriguing questions among researchers. Did it contribute to atmospheric warming or trigger cooling by accelerating mountain erosion? This discovery not only sheds light on a hidden era but also invites further exploration and debate within the scientific community.
