赣东北-浙西北登山群和松木坞群中火山岩的地球化学

GEOCHEMISTRY OF THE VOLCANICS IN DENGSHAN GROUP AND SONGMUWU GROUP FROM NE JIANGXI PROVINCE AND NW ZHEJIANG PROVINCE

赣东北－浙西北新元古代登山群和松木坞群主要由板岩、砂岩、流纹岩、流纹质英安岩、玄武岩和玄武质安山岩组成，火山岩的Ｒｂ－Ｓｒ和Ｓｍ－Ｎｄ等时线年龄以及流纹岩中单颗粒锆石Ｕ－Ｐｂ年龄显示其成岩时代为８００－９００Ｍａ。登山群和松木坞群火山岩呈双峰式产出，其中镁铁质火山岩在化学成分上呈现出演化程度较高的特点（ｅｖｏｌｖｅｄｎａｔｕｒｅ），高强场元素（Ｔｉ、Ｎｂ、Ｔａ等）相对于碱土元素未发生明显亏损，反映其形成于大陆裂谷环境。镁铁质火山岩具低的Ｎｄ值，表明其来源于弱亏损的地幔源，也可能遭受一定程度的地壳混染作用改造。酸性火山岩在化学成分上表现出Ｓ型火山岩特点，但其变化于－１．９～＋２８，指示其为先存的长英质基底分熔作用的产物，但存在强烈的地慢物质添加作用。

The Dengshan Group and Songrmuwu Group in NE Jiangxi Province and NWZhejiang Province are composed mainly of slates, sandstones, sandstones,rhyolitic andesites,basalts and basaltic andesites in Which the volcanics show bindal suite. The volcanics have beendated by Rb-Sr isochron, Sin-Nd isochron and single zircon U-Pb methods and obtained thecrystallization age between 900 Ma and 800 Ma. The basalts and basaltic andesites of DengshanGp. and Songmuwu Gp. exhibit relatively evolved nature in composition and show an enrichmentOf incompatible elements, implying continental rift setting. The rhyolites and rhyolitic daciteswith S-type characteristics have the ENd value from -- 1. 9 to + 2. 8, indicating an origin by partialmelting of old sedimentary protoliths and in-vololving variable amount addition of mantlecomponents.