U.S. West Texas Intermediate crude oil futures are trading only slightly lower for the week despite a steep sell-off on Thursday. After edging higher $3.97 over nine trading sessions, these gains were wiped out in just one day as prices plunged to their lowest level since June 18. The catalyst for the plunge in prices was the announcement of additional tariffs on China by the United States. The news came as a surprise since the two economic powerhouses had just ended its first round of renewed trade negotiations after earlier talks broke off in…