Geological Characteristics Of Cretaceous Volcanic Rocks In Heilongjiang Area,Heihe

This paper takes Cretaceous volcanic rocks in Heilongjiang area of Heihe as the main object of study.This work systematically collected the previous research data,dividing stratum of the Cretaceous volcano rocks in the study area through field regional geological survey,combined with the observation of thin sections,analysis of major elements,trace elements and REE data to comparison stratigraphic unit of Cretaceous volcano rocks in this area,divide volcano stages and lithofacies,discrimination of tectonic setting,discusses the evolution of the relationship between dynamic conditions,volcano and mineralization.The Cretaceous volcanic rocks in the study area are mainly volcanic rocks composed of andesite,dacite and rhyolite,which contain a small amount of basalt,coarse andesite and pyroclastic rocks.The type of volcanic eruption mainly belongs to the central eruption.The volcanic facies are dominated by overflow facies.In the TAS diagram of volcanic rocks,it can be seen that most of the andesite,rhyolite,the second is the dacite and trachyandesite;In the silica alkali diagram,most on alkaline region,only one or two in the basic region;In the F-A-M triangle diagram,most distribution in calc alkaline rocks area,less tholeiitic area;most of K2O-SiO2 variability in the graph into high potassium rocks,tiny amounts distributed in potassium rocks.The distribution pattern of rare-earth elements is all right and the total amount of rare earth is enriched,which belongs to the enrichment type of light rare earth.The fractional degree of fractionation between rare earth elements is high.Due to the enrichment of light rare earth,the loss of heavy rare earth appears accordingly.The trace elements of trace elements show the enrichment of elements such as K,Rb,Ba and Th,as well as Ce,Zr,Hf,and loss of Ti,P,Sr,Y,Yb and other elements.Based on the analysis of Cretaceous volcanic rock association characteristics,petrogeochemical characteristics and discrimination of tectonic setting,the Cretaceous volcanic rocks in this area are formed in the mature continental island arc environment.The magma source area may be a subducted oceanic crust and an ascending mantle.At the same time,since Longjiang period magmatic activity to the strength of Guanghua activity decreased,but only discovery a small amount of neutral-basic volcanic rocks of Ganhe period.The impact of the early Cretaceous subduction of the Pacific plate on the study area is rapidly decreasing.The metal minerals in the study area are represented by rock gold,and are damaged by the late volcanic structure,and the quartz veins of the late hydrothermal activity areas have higher gold grade.Late extrusion plays an important role in the mineralization of gold deposits,which may be the main metallogenic period.