Zircon U-Pb ages and geochemical data of volcanic rocks in the Suifenhe Formation in eastern Heilongjiang Province are reported, and their petrogenesis is discussed in this paper. The Suifenhe Formation mainly consist...Zircon U-Pb ages and geochemical data of volcanic rocks in the Suifenhe Formation in eastern Heilongjiang Province are reported, and their petrogenesis is discussed in this paper. The Suifenhe Formation mainly consists of basalt, andesite, and dacite. Zircon from andesite and dacite are euhedral in shape and show typical oscillatory zoning with high Th/U ratios （0.18-0.57）, implying its magmatic origin. Zircon U-Pb dating results by laser ablation inductively coupled plasma mass spectrometer （LA-ICP-MS） indicate that the ^206Pb/^238U ages of zircons from andesite range within 105- 106 Ma, yielding a weighted mean age of 105.5±0.8 Ma （n=14）, and that ^206pb/^238U ages of zircons from dacite are between 90-96 Ma, yielding a weighted mean age of 93.2±1.3 Ma （n =13）. The volcanic rocks from the Snifenhe Formation are subalkaline series and show a calc-alkaline evolutionary trend with SiO2 content of 47.69%-65.47%, MgO contents of 1.42%-6.80% （Mg^#= 45-53）, and Na2O/K2O ratios of 1.83-3.63. They are characterized by enrichment in large ion lithophile elements （LILE） and lightrare-earth elements （LREE）, depletion in heavy rare earth elements （HREE） and high field strength elements （HFSE） （e.g., Nb, Ta, Ti）, and low initial ^87Sr/^86Sr ratios （0.7041-0.7057） and positive εNd（t） ValUes （0.39-4.08）, implying that they could be derived from a depleted magma source. Taken together, these results suggest that the primary magma of the volcanic rocks might originate from partial melting of the mantle wedge metasomatized by fluids derived from subducted slab under a tectonic setting of active continental margin.展开更多
基金the National Natural Science Foundation of China （Grant No. 40672038） the Special Grant of 0il ＆ Gas Research （XQ-2004-07）.
文摘Zircon U-Pb ages and geochemical data of volcanic rocks in the Suifenhe Formation in eastern Heilongjiang Province are reported, and their petrogenesis is discussed in this paper. The Suifenhe Formation mainly consists of basalt, andesite, and dacite. Zircon from andesite and dacite are euhedral in shape and show typical oscillatory zoning with high Th/U ratios （0.18-0.57）, implying its magmatic origin. Zircon U-Pb dating results by laser ablation inductively coupled plasma mass spectrometer （LA-ICP-MS） indicate that the ^206Pb/^238U ages of zircons from andesite range within 105- 106 Ma, yielding a weighted mean age of 105.5±0.8 Ma （n=14）, and that ^206pb/^238U ages of zircons from dacite are between 90-96 Ma, yielding a weighted mean age of 93.2±1.3 Ma （n =13）. The volcanic rocks from the Snifenhe Formation are subalkaline series and show a calc-alkaline evolutionary trend with SiO2 content of 47.69%-65.47%, MgO contents of 1.42%-6.80% （Mg^#= 45-53）, and Na2O/K2O ratios of 1.83-3.63. They are characterized by enrichment in large ion lithophile elements （LILE） and lightrare-earth elements （LREE）, depletion in heavy rare earth elements （HREE） and high field strength elements （HFSE） （e.g., Nb, Ta, Ti）, and low initial ^87Sr/^86Sr ratios （0.7041-0.7057） and positive εNd（t） ValUes （0.39-4.08）, implying that they could be derived from a depleted magma source. Taken together, these results suggest that the primary magma of the volcanic rocks might originate from partial melting of the mantle wedge metasomatized by fluids derived from subducted slab under a tectonic setting of active continental margin.
