The petrogenesis and geological significance of early Jurassic monzogranites in the Huma area of Heilongjiang Province
By means of petrology,chronology and lithogeochemistry,this article studies the early Jurassic monzogranites in the Huma area of Heilongjiang Province,located in the northeast of the Great Xing'an Mountains,revealing their petrogenesis and tectonic background.The diagenesis time of the Early Jurassic monzogranites in the study area ranges from(176.3±0.8)Ma to(177.7±1.1)Ma,characterized by high silicon,medium to low potassium,moderate magnesium iron,and poor calcium in lithogeochemistry.The rocks belongs to the high potassium calcium alkaline series,enriched in light rare earth elements(LREE)and large ion lithophilic elements(Rb,K,Sr,Ba,etc.),but depleted in heavy rare earth elements(HREE)and high field strength elements(Nb,Ta,Ti,P,Zr,etc.),with no significant negative Eu anomaly(0.70-1.50).Compare to the increase of SiO2,the monzogranites shows a decrease trend in P2O5,with relatively high Sr/Y(9.67-148.07)and LaN/YbN(7.66-54.12)ratios,low Mg #(23.07-39.37),Cr(6.00-11.60)× 10-6,and Ni(4.69-9.39)× 10-6values,indicating the characteristics of 1-type granites.Its Nb/Ta ratio is slightly higher than the average of the continental crust,and the Th content is between the abundance values of the crust and mantle,indicating the addition of mantle derived components.The tectonic background map shows that most of the samples fell into a volcanic arc environment.Based on the distribution characteristics of intrusive rocks of similar ages in the region and its geochemical characteristics,it is speculated that the magma formed in a continental margin arc environment related to the southward subduction of the Mongoli-an-Okhotsk Ocean.
万方数据
维普
