The Research Of Potash-forming Features In Lanping-Simao Basin

The exploration and development works in Lanping-Simao Basin started earlier, and the salt mining has a long history, in which salt resources are rich. Mengyejing potash deposit is the only value of minning solid potash deposit. In this article, based on the works previously, we study the characteristics of geology and geochemistry, in addition to the geological setting, we discuss the ore-controlling factors, the source for metallogenic matters, the salt-forming layers and so on. We also focus on the comparative studies of salt-forming features between the Lanping-Simao Basin and the Nakhon Ratchasima Basin, enhance the realization in salt-forming rules. Main conclusion as follows:(1)Lanping-Simao Basin should be continental rift basin. The basin evolution experienced the rifting period of intense volcanic activity(T2-T3), the faulted period after the cessation of volcanic activity(J-K), the period of drying into salt at Early Tertiary, at the late Eocene, a strong collision occurred between the Ancient Asian plate and the Indian plate, resulting in the basin by squeezing closed, disappear. Potash-forming mainly occurred in late rifting. After the rifting closed, the Indian plate continued to drive, the area subjected to intercontinental transformation as the large-scale strike-slip and thrust.(2) Volcanic rock, ancient salt weathering salt is part of the material sources, and the residue of ancient seawater, deep underground brine and land-based sources water also provides the material basis.(3) On Meso-Cenozoic sedimentary facies and palaeogeography, the paper indicates the Lanping-Simao Basin is Paleocene continental lake sediments, and divides it into three huge facies, five facies and eight subfacies. The salts are from the shallow brine salt lake deposition and playa crystal brine deposition.(4)The Lanping-Simao Basin was located in the low latitude area of northern hemisphere. The age of Mengyejing formation is late Cretaceous, and reveals the formation recorded three main salt-froming period, and the best one located at the bottom, moreover, infers the climate of deposition period was drought overall and changing, and there were three extreme arid climate periods: the bottom of Mengyejing group(profile 780-930 m, characterized by high content of Carbonate, Chloride, Potassium ion and Sodium ion, and low chemical weathering index, and more oxygen isotope); the central section of Mengyejing group(profile 300-390 m, characterized by high content of Carbonate, Chloride, Potassium ion, Sodium ion and MgO/CaO, and low chemical weathering index); the top of Mengyejing group(profile 30-150 m, characterized by high content of Carbonate, Chloride, Potassium ion and Sodium ion, and low chemical weathering index, and more oxygen isotope).By the study of fators of potash-forming, and the evolution of potash-forming, we have a more profound understanding of the geochemical characteristics of salts, the genetic type of potash, formation mechanism and sedimentary characteristics of the potash, in order to provide a reference for potash searching and minning.