Scientific Drilling at Sulphur Springs, Valles Caldera, New Mexico: Core Hole VC 2A



A scientific core hole has been drilled into the western ring fracture zone of the Valles Caldera, N.Mex. Hole VC-2A, the second scientific core hole in the caldera, was cored through a faulted and brecciated sequence of intracaldera tuffs and volcaniclastic rocks to a depth of 528 m at Sulphur Springs. As of November 1, 1986, the unequilibrated bottom hole temperature was 212°C. The rocks that have been penetrated are intensely altered and contain molybdenite mineralization (MnC>2) that is less than or equal to 1.1 m.y. in age. The active hydrothermal system at Sulphur Springs consists of a thin (5-m) acid condensation zone overlying vapor- and water-dominated zones. The latter two zones are apparently separated by a region of tightly sealed rock.