The estimated total gold reserves at the Xiling gold mine in Shandong province has risen to about 592.2 metric tons after a new discovery of more than 200 tons of the metal in the mine, according to Shandong Gold Group Co, which held a news conference on Thursday morning to announce the discovery.

The gold reserves have a potential value of more than 200 billion yuan ($27.7 billion). The discovery makes Xiling the largest single gold reserve mine in China, the group said.

The group announced in 2017 that it had detected 382.6 tons of gold in the mine. It also discovered 590 tons of silver.

Located in Laizhou city, the mine is part of the Jiaodong Metallogenic Region, which is one of the largest gold production areas in China, with gold reserves and output ranking first in the country, Li Hang, general manager of the group, said at the news conference.

Gold reserves in the mine are mainly distributed at a depth of 1,000 meters to 2,500 meters, making Xiling the deepest gold mine in China, Li said.

The body of gold ore at the Xiling mine extends more than 2,050 meters. One section has a thickness of 66.52 meters. The ore has an average gold yield of 4.02 grams per ton, Li said.

"The Xiling gold mine is expected to maintain production for about 40 years, if its annual processing capacity is 3.3 million tons," he said.

It has been 23 years since the group began exploring the mine, during which it has invested about 880 million yuan in exploration activities.

Explorers have drilled 180 boreholes with a total length of more than 300,000 meters. The deepest exceeded 4,006 meters in depth. Fifty of the boreholes reached 2,000 meters.

The discovery and exploration of the Xiling gold mine has great economic and scientific value and is of great significance for the development of China's gold industry, the group said.