AAPG ANNUAL MEETINGNew Orleans, LouisianaApril 25-28, 1993

As the archetype continent-continent collision, the Himalaya and Tibet Plateau have long been a prime candidate for deep seismic reflection profiling. Last summer the pilot phase of a multi-year program to profile this unique region was undertaken by a team of scientists from China's Ministry of Geology and Mineral Resources (MGMR) and Cornell, Syracuse, Stanford and Columbia universities in the United States. Approximately 100 km of deep reflection data were acquired by a "contract" MGMR seismic crew. Wide-angle and offline recordings were made using portable REFTEK seismographs supplied from the U. S. The main CMP profile was recorded to 50 sec with a 120-channel DSF-V with 50 m group intervals. 50 kg shots spaced at 200 m along the line and 200 kg charges spaced at 6 km provided th seismic source. A field data processing system supplied from the U. S. allowed for initial analysis of the data in the field.

Despite extreme altitude and difficult drilling conditions, a number of exciting observations have been made. These include: (1) A prominent gently north-dipping reflection at about 30-35 km depth, that may mark the active detachment between India and Asia beneath Tibet, and (2) several prominent bands of reflections at about 75 km depth that likely come from the base (Moho) of the roughly double thickness continental crust that underlies the region. Although preliminary, the results to date, demonstrate that CMP profiling using modest charge sizes and conventional recording systems can effectively image structure throughout the very thick crust of the Tibet Plateau. We look forward to more work in this exciting region in the near future.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.