linguistic:paraphrasing, structural:expansion
Resources

Tianjin Municipality has deposits of about 1 billion tonnes of petroleum, with Dagang District containing oilfields. Salt production is also one of the city's industries, with Changlu Yanqu being one of China's salt production areas. Geothermal energy is another resource of Tianjin. Deposits of manganese and boron under Tianjin were the first to be found in China.