Jasperite Geological Characteristics And Iron Sedimentation-mineralization Model Study Of Shilu Iron Ore Deposit In Hainan

Shilu iron deposit in Hainan Province was known as "the largest iron-rich ore deposit in Asian" because of the high grade of iron ore. Its tectonic position belongs to the western of Wuzhishan fold belt in South China fold system and the intersection of nearly EW to Changjiang-Qionghai deep fault and the NE to Gezhen ductile-brittle fracture. In the region, exposed strata are mainly Paleozoic and secondly Proterzoic,Mesozoic and Cenozoic. New archean-Paleoproterozoic strata are exposed at Wuzhishan and Sanya in the southeastern of the island. Cambrian, Devonian, Permian and the Jurassic sediments are nearly missing in northwestern of the island while southern of the island is lack of Permian strata. The widespread magmatic rocks consist of granite of late Hercynian-early Yanshan and late Yanshan.The region is rich in more than50kinds of mineral resources including the iron,copper,lead,zinc,gold.Strata exposed at the center of the mining are mainly Jixian-Qingbaikouan Shilu Group and the Sinian Shihuiding Formation; the eastern of the mining are the Carboniferous Nanhao Formation and Qingtianxia Formation, the Permian Echa Formation, Eding Formation and Nanlong Formation.The whole mining is controlled strictly by the Shilu multiple syncline,which consists of Beiyi syncline,Hongfangshan anticlinal,Shihuiding syncline. In addition,fault structures are divided into three groups including NW-NNW, NEE-EW and NNE-SN.The mining are surrounded by biotite monzogranite from the north and south and granite porphyry from the west. The main iron ore bodies are Beiyi,Nanliu and Fengshuxia that are more than90%of the total reserves made up of38ore bodies.The ore bodies are mostly hosted with layered and resembles layered in the sixth layer of Shilu group and controled drape structure distortion,while several assumed the vein and the fault contact with the stratum.The ore types of Shilu iron deposit include massive quartz hematite ore,massive pyrite magnetite hematite ore and skarn type ore. Metallic minerals consist of hematite, magnetite and secondary minerals pyrite as well as minor limonite; Gangue minerals are mainly composed of quartz and secondary minerals sericite,jasper,calcite,epidote and a small amount of skarn minerals ,such as garnet,diopside,tremolite. The main ore structures include massive structure, schistose structure, vein structure, disseminated structure and brecciated structure; ore textures include tiny flaky texture, lepidoblastic texture, edge texture, replacement texture, self-crystal and half self-crystal texture, fractal texture. The alterations developed in wall rock mostly not only include tremolitization, diopsidization,but also garnetization,epidotization,silicification, carbonation and show a part of alteration zoning. The deposit can divided into five metallogenic phases:exhalative sedimentary phase,metamorphic phase,hydrothermal phase and supergene phase, whlie hydrothermal phase is further divided into high-temperature hydrothermal stage, the iron oxide stage and the mid-low temperature hydrothermal stage.Jasperite is typical plume rocks which belongs to iron-containing siliceous rocks.It’s the product of submarine volcanic exhalation-sedimentation and also important petrology symbol of this type of deposit. Jasperite exposured in the mining is mainly spread in quartz hematite ore as lensing or raindrop. Jasperite is usually blood red or brown-red, compact massive structure and maily consist of aphanitic quartz, terrigenous elastic quartz, jasper and hematite.The diagrams and contrast research based on the major and trace element geochemical data indicate that: jasperite of Shilu iron deposit is the product of hydrothermal sedimentation.The hydrothermal water forming jasperite is similar to what’s in the mid-ocean ridges which is slant acidity and reducing. Hydrothermal water with these characteristics are rich of silicon and iron.The hydrothermal water will change to alkaline, oxidation and cold while its remove and the relativly Alkalescent,oxidation and colder sea water.And the colloid of SiO2and Fe(OH)3will gather and form jasper at suitable PH、Eh and temperatures.Kinds of geological character of Shilu iron deposit and study results of Jasperite show that it responsives to submarine volcanic exhalation-sedimentation mineralization.It’s a volcanic related deposit and form mainly because of sedimentation mineralization. Proximal transport and diversity mechanism explains the metallogenetic process of Shilu type submarine volcanic exhalation-sedimentation mineralization and a exploratory metallogenic model has builded depend on these.