The Research On The Tectono-thermal Events In The Basin Group Of Eastern Heilongjiang Province

The basin group of eastern Heilongjiang Province, including Jixi, Huling,Sanjiang Basin and Tangyuan, Fangzheng Downfaulted Basin ,et al, lies close tothe Heilongjiang River to the north, the Dunmi Fracture to southeast, theMudanjiang Fracture to southwest, the Wusuli River to east, the Yi-Shu Fractureto northwest. The basin group is located on the Jiamusi paleouplift with the areaof 58830km2. The coal measure strata consist of Chengzihe Formation andMuling Formation of the lower Cretacic , the Paleogene. The volcanic rocksinclude Dongshan Formation and Songmuhe Formation of the Cretacic, the upperTertiary. The aim of the paper is to clarify the periods of the tectono-thermal eventin basin group of eastern Heilongjiang Province, to distinguish the source rocksformation which influenced by each tectono-thermal event, and to discuss theorganic thermal evolution degree. These will provide necessary data forresearching the relationship between the tectono-thermal event and the oil and gasgenerating,accumulating and conservating, and evaluating the resource of oil andgas.In this paper, abundant data of the present ground temperature andreflectance of vitrinite are used. Many methods and techniques are utilized, e.g.thermal decomposition and color spectrum-mass spectrum (CS-MS) analysis, thinsection identification, reflectance of vitrinite testing, illite crystallinity testing,clay minerals X-ray diffraction analysis, fluid inclusion homogeenous temperaturetesting, laser-Raman spectrum analysis and fluorescence microscope analysis.It is considered that the method of the paleotemperature recovered withreflectance of vitrinite is suitable accoding to synthetizing all kinds of methodsand theories of paleotemperature recovery and the data related to temperature. Itis indicated that Hood graephical and TTI are better through the correlationamong paleotemperature recovery methods with reflectance of vitrinite. Finally,fluid inclusion homogeenous temperature, illite crystallinity indicatingtemperature and montmorillonite-illite transforming temperature are almostconsistent with the paleotemperature calculated according to Huangkexingformula(1990) based on the Hood graephical. Accordingly, Huangkexing formula,T=-4.9+4.46E+0.064E2,E=26.7lg(Ro)+22.3, is used to calculate paleotemperaturein this research.Under present ground temperature field, it is concluded that the Paleogenepaleotemperature is higher than the present according to the correlation betweenthe present ground temperature and the paleotemperature recovered by reflectanceof vitrinite and the coal rank respectively. This reason is the upper Tertiary basalteruption caused by the activity of Yi-Shu Fracture and Dunmi Fracture. Therefore,the stage of tectono-thermal event happened during the upper Tertiary presumedly.it is concluded that the lower Cretaceous paleotemperature is higher than thepresent, but similar with the Paleogene paleotemperature according to thecorrelation between the paleotemperature recovered by reflectance of vitrinitepro-degradation recovery and the present ground temperature , thepaleotemperature temperature .The result is caused by the laevogyrate strike-slipof Yi-Shu Fracture and Dunmi Fracture, and the increasement of volcanicactivities from Chengzihe Formation to Dongshan Formation. this tectono-thermalevent is named Dongshan tectono-thermal event, because of the wide distributionof Dongshan volcanic rocks.Source rock formations influenced by each tectono-thermal event isrecognised by contrasting the Paleogene and the lower Cretaceouspaleotemperature with the present temperature, and the Paleogenepaleotemperature with the lower Cretaceous paleotemperature in the same burialdepth by use of the maximal hypothesis and exclusive method. It is indicated thatthe present temperature field has no effect on the Paleogene and the lowerCretaceous source rock formations;the upper Tertiary tectono-thermal event hadenhanced the degree of maturation of the Paleogene source rocks, but had noeffect on the lower Cretaceous source rock formation;the lower Cretaceoussource rock formation was affected mainly by the Dongshan tectono-thermalevent.The degree of maturation of source rock is studied by reflectance of vitrinite,the thermal decomposition maximal temperature, organic geochemistry analysisand the oil and gas indication. It is concluded that the upper Tertiarytectono-thermal event had enhanced the Paleogene stratum temperature of easternbasin group, and caused the degree of maturation of source rock evolving fromimmaturity to maturity. The Dongshan tectono-thermal event had caused thedegree of maturation of Chengzihe Formation and Muling Formation source rockevolving from lower maturity to overmaturity.