MIOCENE DIACHRONIC UPLIFT ALONG THE AILAO MOUNTAINS-RED RIVER LEFT-LATERAL STRIKE-SLIP SHEAR ZONE
Chen Wenji, Li Qi and Wang Yipeng(Institute of Geology , State Seismological Bureau, Beijing}
The Ailao Mountains-Red River shear zone is located in southern Yunnan province. To better understand the nature and timing of this zone, 40Ar/39Ar age spectrum analyses were undertaken on 18 K-feldspars samples from six sites. Interpretation of the analytical results using the MDD model (multiple-diffusion domain model) yields 18 cooling curves in the temperature range of 400-150℃. All these curves have one (or two) rapid cooling process (with a cooling rate100℃/Ma). The rapid cooling (uplift) event not only reflects the termination of ductile deformation and beginning of normal faulting along the shear zone at about 25 - 17 Ma B. P. but also shows that its starting time had a northwestward-younging trend. When plotted as a function of the distance along the range, the starting time of rapid cooling (uplift) at the six site decreases linearly at a slope of 34mm/a. Two different tectonic interpretations may possibly accounts for this good linear functional relationship.
【CateGory Index】： P542.2