SYDNEY—Australia is not shut to Chinese investors but national security concerns and the protection of critical infrastructure are now key factors determining deal approvals, the head of its Foreign Investment and Review Board (FIRB) said on Thursday. Chinese investment in Australia has fallen by over 50 percent to about A$12 billion ($8.86 billion) over the past four years, driven by stricter capital controls by Beijing, and by a deterioration of the relationship between the countries. “We run a non-discriminatory investment policy… both in terms of areas in which you can invest … [and] in terms of the provenance, the country from which the investment comes,” said FIRB Chair David Irvine at the Citi Investment Conference. He highlighted that 20 percent of approved transactions in the past year had some form of Chinese participation. “We continue to welcome investment applications from Chinese interests. If they’re in areas of national security interest, …