The collapse of a portion of a salt dome that left a 37-acre sinkhole in swampy land west of Baton Rouge has bubbled up into a $50 million dispute between the mine operator and its insurance company. Texas Brine LLC wants the Louisiana insurance commissioner to order New York-based Liberty Insurance Underwriters Inc. to pay off on the policy, which was to kick in after the company’s other insurers paid more than $75 million in claims in the collapse. Texas Brine claims the limit has been reached.