| The Lucaogou Formation in the Santanghu Basin of Xinjiang develops a set of dark fine grained sedimentary rocks rich in oil and gas,mainly based on the deep-semi deep lake sedimentary environment.After a long period of research,it was found that there were a lot of materials related to volcanism and magmatism in this formation,including dolostone related to mantle-originated exhalative hydrothermal activities,calcite rock related to exhalative hydrothermal activities,tuff mudstone and micrite,etc.Due to the very fine grain size of the sediment in the Lucaogou Formation,it is difficult to study the fine grain directly,Therefore,this article from the perspective of siliceous rocks in the dark rock series of Lucaogou Formation,combined with the method of petrology,mineralogy,fluid inclusions and a variety of geochemical methods,analysis of environmental and genetic model of the siliceous rocks,and for the study of Lucaogou Formation sedimentary environment,It provides more evidence to enrich the magmatic hydrothermal types of the Permian Lucaogou Formation,The result and understanding are as follows:1? The siliceous rocks of Lucaogou Formation can be divided into six types: deformation intervals,intervals,plaques,lensing,and clumps,they all have the penecontemporaneous structure deposition.and all of them are made up of microcrystal quartz and chalcedony.The crystal morphology is dominated by semi-idiomorphicheteromorphic crystals,The results of cathode luminescence show that siliceous minerals are generally no luminescent,which represent that they are formed at low temperature.2? With the study of the silicon isotopes,electron probe and fluid inclusion,we found that the silicon isotope ?30Si value range was-0.7-0.7‰,which belonged to hydrothermal silicon rock,The negative value represented that the silicon mainly came from the Mantle-derived magmatic hydrothermal fluid,while the positive value represents normal hot water deposition.The electron probe results showed that the siliceous rocks were rich in Sr O,and the values of K2O/Na2 O were all less than 1,indicating that the genesis of the siliceous rocks in Lucaogou Formation was closely related to the action of underwater volcanic hydrothermal activities,The temperature range of fluid inclusions is 96.4-367.1?,which can be divided into three phases,which indicates that the fluid activity has multiple phases.3?According to the comprehensive analysis,the source and genesis of siliceous rocks in lucaogou formation can be mainly divided into two types.The first type is the sedimentary period of lacustrine mudstone.Due to the influence of magmatic hydrothermal activities,the magmatic hydrothermal fluid carry a large amount of Si O2 into the lake basin,Si O2 supersaturated deposition forms siliceous rocks.The second is the intermittent period of magmatic hydrothermal activity,in which the whole lake basin is in a calm state.As the temperature of the lake increases,Si O2 is deposited to form siliceous rocks under conditions similar to hot spring water.4?Through the study of siliceous rock formation and the sedimentary environment,It can be reflect that this set of the fine sedimentary rocks in Lucaogou Formation was extensively influenced by the magmatic hydrothermal activities.and belong to a special class of mudstone controlled by the deep material,which can be used as a typical target for the future research on the relationship between deep material and organic matter. |
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