[Geological distribution of exudation and storage area of Tibetan medicine Zha-xun in Sichuan province based on GIS].

Zha-xun is widely used in Tibetan medicine and is also an international traditional medicine. This study believes that the black organic matter constituting Zha-xun is mainly stored in the rocks. The exudation points of Zha-xun mostly distribute on the cliffs of high mountains, which makes it difficult to evaluate its resource distribution and storage area. This paper was aimed at the exudation environment of Tibetan medicine Zha-xun in Sichuan province and 6 ecological environmental factors of the Zha-xun were determined via the field investigation. Combining with these 6 factors as well as the GIS data of Sichuan province, ArcGIS software was used to extract ideal environmental factors which are suitable for exudation of Zha-xun, including geology types, geomorphological types, altitude, slope, vegetation types, and mean annual temperature. The spatial overlay analyses on the extracted environmental factors were carried out to predict the distribution area of Zha-xun in Sichuan province. Afterwards, field investigation was conducted to verify the prediction. The prediction showed that the exudation spots of Zha-xun in Sichuan province mainly located in 29 counties including 12 in Aba Prefecture, 15 in Ganzi Prefecture, and Muli County and Dechang County in Liangshan Prefecture. The deposit areas of Zha-xun were located in the Triassic, Devonian and Silurian strata and were basically distributed in 9 basins, including Dingqu River, Yalong River, Xianshui River, Dadu River, Suomo River, Minjiang River and Baishui River, characterized by a fragmented patch-like distribution along the mountain ranges, and the exudation spots of Zha-xun were mainly scattered among the rain-free cliffs' concavities of river valleys at a certain altitude. The prediction was consistent with the field investigation results, which suggested that it is possible and feasible to predict distribution of Zha-xun resources based on GIS-analysis. The study may provide a scientific basis for comprehensive investigations into Zha-xun's distribution and formation mechanism, thus promoting rational development and utilization of Zha-xun resources.