CAJ | 학술논문

松辽盆地徐家围子营城组发育一套以流纹岩为主的中酸性火山岩.岩石薄片观察和主量、微量元素研究发现,后期热液蚀变、区域埋深及低温水合作用对流纹岩的Si、K、Rb等元素含量产生一定影响;流纹岩明显富集Rb、Th、U、Pb等强不相容元素,Ba、Sr、Tj、Eu、P负异常,暗示其经历了斜长石、磷灰石和钛铁矿分离结晶作用.流纹岩的(~(87)St/~(86)St);(0.705265～0.711895)值变化范围较大,大多数ε_(Nd)(t)为正值(1.83～3.38),Pb同位素比值相对集中,(~(206)Pb/~(204)Pb)_i=18.09～18.32,(~(207)Pb/~(204)Pb)_i=15.50～15.54,(~(208)Pb/~(204)Pb)_i=37.80～38.10.研究表明,岩石的源区为大比例年轻成分与少量古老地壳的混合部分熔融,其演化过程中经历了不同程度的地壳混染.松辽盆地早白垩世火山岩为板内伸展环境喷发的产物,可能与太平洋板块俯冲导致的中国东部岩石圈减薄、软流圈上涌密切相关.
송료분지서가위자영성조발육일투이류문암위주적중산성화산암.암석박편관찰화주량、미량원소연구발현,후기열액식변、구역매심급저온수합작용대류문암적Si、K、Rb등원소함양산생일정영향;류문암명현부집Rb、Th、U、Pb등강불상용원소,Ba、Sr、Tj、Eu、P부이상,암시기경력료사장석、린회석화태철광분리결정작용.류문암적(~(87)St/~(86)St);(0.705265～0.711895)치변화범위교대,대다수ε_(Nd)(t)위정치(1.83～3.38),Pb동위소비치상대집중,(~(206)Pb/~(204)Pb)_i=18.09～18.32,(~(207)Pb/~(204)Pb)_i=15.50～15.54,(~(208)Pb/~(204)Pb)_i=37.80～38.10.연구표명,암석적원구위대비례년경성분여소량고로지각적혼합부분용융,기연화과정중경력료불동정도적지각혼염.송료분지조백성세화산암위판내신전배경분발적산물,가능여태평양판괴부충도치적중국동부암석권감박、연류권상용밀절상관.
The intermediate-felsic rocks, mainly rhyolites, are widely distributed in Yingcheng Formation in Xujiaweizi, Songliao Basin. Petrological, major and trace elements geochemistry studies exhibit that the content of many elements (e. g. St, K, Rb) of the rhyolites is a little influenced by burial and regional metamorphism, low-temperature hydration and hydrothermal alteration. The rhyolites are prominently enriched strongly incompatible elements such as Rb, Th, U, Pb, and have apparently negative Ba, Sr, Ti, Eu, P anomalies, which indicate the rocks were produced by fractional crystallization of plagioclase, apatite and ilmenite. The rhyolites have high and wide initial ~(87)Sr/~(86)Sr (0.705265～711895) ratios. Most ε_(Nd) (t) values of the rhyolites are all positive and have a narrow range (1.83～3.38), but they have an analogical radiogenic Pb ((~(206)Pb/~(204)Pb)_i = 18.09～18.32, (~(207)Pb/~(204)Pb)~i = 15.50～15.54, (~(208)Pb/~(204)pb)_i =37.80～38.10). The features of isotopic data indicate that the primary magmas were derived originated from a mixed source by juvenile component and ancient crust, but contaminated by the crust in different level during evolution. The rhyolites may erupt in extensional setting within plate in the Early Cretaceous, and were probably associated with the lithospherie thinning and asthenospheric mantle upwelling by subduction of the Pacific plate beneath eastern China.