Study Uncovers How Gold Formed in China's Tianshan Mountains

A new study led by Prof. XIAO Wenjiao from the Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences has shed light on the ore-forming process and key mechanisms of the gold deposit in South Tianshan, Northwest China. The study was published in Geological Society of America Bulletin on Jan 20.

The Tianshan Orogenic Belt is the world's second-largest gold-rich region. The researchers focused on a massive gold deposit known as Sawayaerdun. This region is estimated to contain a staggering 3.7 million ounces of gold, though the gold is spread thinly, averaging about 1.38 grams per ton.

However,how this gold originally formed, where it moved from, and the exact concentration processes, remained a scientific puzzle.

To solve this puzzle, the researchers used advanced tools to identify the microscopic changes of elements and their isotopes in the gold-bearing minerals.

They found that the initial "pre-gold" stage, where gold became concentrated in those early-formed pyrite minerals within the dark rocks, was surprisingly crucial. This early enrichment set the stage for the massive gold deposit we see today.

Theyalso highlighted a critical process where fluids carrying gold underwent a kind of "phase separation," like oil and water separating, which helped to concentrate gold in these "orogenic" deposits.

This fluid phase separation process shows lower average gold grade (averaging 0.66 parts per million of gold). However, it accounted for over 80% of the total ore volume and makes up about 38% of the total gold resource in the region.

"Our findings provide critical guidance for gold exploration in the Tianshan Orogenic Belt and elsewhere," said MA Guoxiong, the study's first author.

Read the full article:https://doi.org/10.1130/B38623.1

Contact

LONG Huaping

Xinjiang Institute of Ecology and Geography

E-mail: longhp@ms.xjb.ac.cn