| As one of the primary metallogenic belts in china, the south-central segment ofDaxinganling, where Mesozoic volcanic rocks consititute intracontinental giant volcanicrocks zone in eastern Asia, draws the whole world’s attention for its scale and tectonicposition. Researchers have made common views about its superiority for its geologicalbackground of petrogenesis and mineralization. Late Jurassic is the most intensive period ofvolcanic activity in this area, producing massive volcanic rocks, which consitituted themain body of Daxinganling. Its formation have a close relationship with complex kinetics,geochemical process， including Paleoasian domain tectonic evolution, deep mantlegeochemical process and tectonic field evlution of Pacific Ocean. In addition, the formationof large-scale orogenic belt and crustal evolution diagenesis and mineralization shouldclosely related to that Late Jurassic large-scale eruptive activity of volcano and its teconicenvironment, crustal evolution process.In this area, volcanic activity proceeded in the alternative way of vocanic overflowfacies and overflow facies. Beaded volcanic apparatus distributed nearly in equal distance,showing Late Jurassic volcanic activity was obviously controlled by fracture pattern,which formed in the background of asthenosphere bump, extensive underplating occurredin the bottom of crust, meanwhile lithosphere extension caused volcanism and formedtectonic framework of regional basin and range, which is different from extrudingenvironment in the north segment of Daxinganling.As the south-central segment of Daxinganling is a kind of special geological tectonicsetting combined by several blocks, along with the discoveries of large, extra largepolymetallic deposits in recent years, we need to observe continental volcanic activity, dosome researches on the volcanic magma tectonic activities belt and the distribution ofsimultaneous volcanic rocks and subvolcanic rocks so as to look for volcanogenic deposit.We found that the distribution of volcanic rocks and tectonics restricted mutually, regionalfault structures often controlled the distribution of volcanic rocks and metallogenic belt;researches on the characteristics of volcanic rocks laid the foundation for determiningvolcanic apparatus and early volcanism and guiding prospecting.It is the most foudamentaland fatal direct factor of studying on vocanic rocks and Late Jurassic crustal evolution.Recently, with the south-central segment of Daxinganling Mesozoic volcanic rocks ofdifferent rock types mating chemical analysis data and the high-quality results of trace elements analysis reported one after another, ore-forming pattern has became a kind ofpossibility.Based on field work, combined with previous research results, from systematicstudies on petrology and lithogeochemistry of Late Jurassic volcanic rocks in the southsection of Daxinganling. This paper suggests preliminarily that Late Jurassic volcanic rocksformed in the action of lithosphere extending fast and asthenosphere bumping, whenvolcanic basin accumulated in the basin-range structure, undergoing at least13volcanic-sedimentary cycles, which is mainly constituted by volcanic rocks and pyroclastic rocks.Late Jurassic volcanic rock series, from bottom to top, lithologic evolution of acidâ†'neutralâ†'acidâ†'neutral corresponds to the change law of smallâ†'largeâ†'middleâ†'small of theaverage total amount of∑REE. REE pattern curve of rhyolite of Manketouebo Fm andearly foyagranite are similar, so are the andesite of Manitu Fm and syenogranite, rhyolite ofBaiyingaolao Fm and alaskite. Therfore, indicating their homologous characteristics have aclose relationship with magmatic activity. And then genetic features of Late Jurassicvolcanic rocks and crustal evolutionary history in the south-central segment ofDaxinganling are promoted, which lay foundations for further studying on the metallogenicmechanism of Daxinganling and guiding mineral exploration. |
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