| "Sanjiang" area is one of the important non-ferrous metal metallogenic belt regions in China,while Lanping Basin is located in the central part of Changdu-Lanping-Simao Basin of Sanjiang metallogenic belt, and has a significantly metallogenic and prospecting potential, e.g. the Jinding lead and zinc polymetallic deposit, which is super large, and other large-middle deposits have been found. Based on the systematic analysis on available geological data, multidisciplinary theories and techniques of petrology, tectonics, mineral deposit geology, mineralogy, element geochemistry,ore-forming fluid geochemistry and isotopic geology comprehensively have been used in the present paper, the main metallogenic factors and basinal development of Lanping ore deposits enriched province are discussed, its metallogenic series is classified, the metallogenic models is established and the future prospecting target areas are proposed by analyzing metallogenic conditions. The main conclusion and results of the present paper are as follows:1) Studies on the main metallogenic factors show that the primary faults are the main pathways of the ore-forming elements, and control the distribution of ore fields; the secondary faults are the distributive structure, and control the forming of ore band and deposit; the third faults are the storage region where the ore-forming materials enrich.2) By analyzing the tectonic evolution of the Lanping Basin, it shows that the four stages,which are rift period, depression period, foreland basin and basin-mountain transition period, can be obtained.3) Systematically researching on the tectonic development of Lanping basin, and basing on the characteristics of deposits, the studied ore deposits can be divided into two metallogenic series and five sub-series. The metallogenic series include lead, zinc, copper, silver deposits which have relation to the deposition in the Yanshan Period and lead, zinc, silver, copper, cobalt deposits which are in connection with deposition, packing action, metasomatism of the basin-mountain transition in the Himalayan Period. The metallogenic series in the Yanshan Period are consist of three sub-series, which are lead, zinc, silver, copper deposit sub-series related to marine jet flow deposition in rift basin stage, copper, lead, zinc deposit sub-series related to marine-lacustrine deposition in basin depression stage and copper, silver, lead(zinc) deposit sub-series related to acustrine deposition in foreland basin stage. An the metallogenic series in the Himalayan Period are consist of two sub-series, which are lead, zinc deposit sub-series related to deposition in basin-mountain transition stage and silver, copper, lead, zinc, cobalt deposit sub-series related to packing action and metasomatism in basin-mountain transition stage.4) The characters of the ore-forming fluid in studied area are showed as follows:The inclosure homogenization temperature is 82 ? 412.4 ? and less than 200 ?commonly,fluid salinity is 5.7 ?21.2 wt % NaCl, generally for 20 wt % NaCl,density is 0.72 ?1.13 g/cm3,generally for 1.00 g/cm3.The main inclosures compositions are H2O-CO2 and H2O-CO2-NaCl, which the CO2 in the fluids indicates the high pressure in the rift and depression period, are KCI-CaCl2-H2O,CaCl2-H2O and NaCl-MgCl2-H2O in foreland evolution period, and are MgCl2-NaCl-H2O,CaCl2-NaCl-H2O in the basin-mountain transition stage. The inclosure fluids in the period from the depression to basin-mountain transition have the typical characters of brine thermal fluid.5 ) The metallogenic models about studied area are showed as follows:In the late of Triassic, marine deposition stage of the pull-apart basin, ore-forming fluids from the deep of the basin base uplifted along the secondary fractures and flowed into the sub-bottomland for deposition, and the ore deposits and ore belts were oriented. In the Jurassic-Cretaceous, the lacustrine deposits developed mainly for the uplift of the basin caused by the extrusion environment, and the ore-forming fluids flowed into the basin along the secondary fracture for deposit mineralization. Besides the deposit ore-body, main ore-forming elements, which provided the resource for ore forming in the later alteration and superposition,were relatively rich in the strata of the basin. And these elements were from the deep of the basin base mainly and the inner basin partly. In the basin-mountain transition period, east-west direction collision happened caused by crush, and the conditions which mountain alternated with basin came into being in the Lanping Basin. The fluids moved along the secondary fractures, and deposit metallization in the basin which is formed in the anterior borders the second fractures,acking action and metasomatism metallization in the secondary nappe fractures and third class fractures happened. In this phase, lead was form the lithosphere, sulfur and mineralizing fluids were form the inner of the basin mainly.6) The studies on mineral exploitations show that the secondary fractures are the ideal areas for exploration. More attention should be paid for fractures and their sides to find the ore beds had relationship with deposition alteration and acking action and metasomatism metallization.Especially, the developing regions of limestones, sandstones and tectonic breccias and the regions with chemical prospecting singularity have the better ore exploration prospect.In this paper, the division of metallogenic series, the analyses of properties of ore-forming fluid and the source material and the discussion on ore-forming process, have significance at some extent for prospecting theories; while the analyses of the main control factors, the establishment of the metallogenic model and metallogenic prediction, have guiding significance for further ore-prospecting. The better results and clues about the ore exploration have been obtained in some areas based on the theory and thought mentioned above. |
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