PETROGRAPHIC ANALYSIS OF CUTTINGS FROM THE YATES #2 LA MESA WELL AND IMPLICATIONS FOR THE TECTONIC HISTORY OF THE SOUTHERN ESPANOLA BASIN

The 2350 m (7710’) Yates #2 La Mesa well, west of Santa Fe, is surrounded by a considerable amount of controversy because of different interpretations of formations present in the well. Petrographic analysis of 46 thin sections of cuttings is underway to resolve these controversies, and their implications for the tectonic history of the southern Española basin. The are rocks rich in and clinopyroxene. These rocks lithologically correlate to basanite and basalt lava flows of the Cieneguilla "limburgite" that crop out near La Cienega. The great quantity of vesicular tachylite and sideromelane glass (some replaced by zeolite) implies proximity to a vent. The lower 307 m (5012'-6018') of volcanic material resembles the latitic lava flows and sedimentary deposits of the Espinaso Formation.