Department of Defense report pointing to several trillion dollars worth of minerals (2010): https://www.reuters.com/article/afghanistan-mining-idUSLDE65...
State Department plan for "New Silk Road" (2011): https://www.theatlantic.com/international/archive/2011/11/cl...
The latter was also about promoting the TAPI pipeline route for moving Central Asian oil and gas directly to the Indian Ocean, a project once meant largely for Chevron and Exxon (major operators in Kazakhstan) exports but which now appears to have been taken over by China:
https://www.hindustantimes.com/world-news/china-joint-statem...
China's approach to obtaining deals in Afghanistan appears to be strictly economic and diplomatic; there are no Chinese soldiers in the region.