新疆北天山泥火山固体喷出物特征及成因机制初探

STUDY ON THE SOLID PRODUCTS FROM MUD VOLCANO IN NORTH TIANSHAN MOUNTAINS,XINJIANG AND DISCUSSION ON ITS GENETIC MECHANISM

北天山泥火山位于新疆天山北麓山前拗陷带内,均处在背斜褶皱的轴部.在了解泥火山的地质背景、活动现状的基础上,对该区泥火山进行了详细的野外考察,对所采样品进行粒度、显微形貌及成分分析.研究发现：该区域的泥火山样品粒径主要集中在0.3～ 100μm,平均值相近,分选较差,分布对称性呈极正偏.矿物颗粒以石英、长石为主,基质为黏土矿物,白杨沟和艾其沟样品中均含有铁矿物质.根据上述分析结果对北天山泥火山成因机制进行了初步探讨,认为该区域的泥火山物源相同,泥浆最深来源于下中侏罗统,地层压力以构造活动为主.目前泥火山处于弱活动期,短期内造成较大灾害的可能性很小.

The mud volcanoes are located in the piedmont downwarp belt of the North Tianshan Mountains in Xinjiang, and all developed at the axis of the anticlinal fold. In this study, based on the geological background and activity of mud volcanoes, we carried out a detailed field investigation on these mud volcanoes at four sites, including Baiyanggou, Aiqigou, Dushanzi and Huoerguosi, and analyzed the particle size, microscopic morphology and composition of the collected samples. The results show that the eruptive types of these mud volcanoes in this area include mud cone, mud shield, mud basin, mud pool and mud hole. The mud liquid surfaces are calm, and bubbling frequency is low. The largest diameter of the nozzle is 2.5m, and the farthest distance of discharged mud flow is about 6.5 meters. The particle sizes of the samples with the similar average sizes are mostly in the range of 0. 3 1001xm, the medium sizes focus on 5 ~ 10~m, and all of the samples are characterized by poor sorting. The column diagrams are generally unimodal distribution and the samples show quite positive skewness in particle size distribution symmetry. The matrix is composed mainly of clay minerals, containing 〈15% mineral grains mainly of quartz and feldspar, and there are some iron particles in Baiyanggou and Aiqigou samples. According to the analyses, it is proposed that the mud volcanoes in North Tianshan Mountains have the same material source, which is from the middle-lower Jurassic strata, and the high pressure in the strata can be attributed mainly to tectonic activity in the region. At present, the activity of mud volcanoes is relatively weak, and it is unlikely to cause a serious disaster in the near future.