The western margin of Yangtze block and southwestern Sanjiang region absorbed much attention from geologists. It has been proved that there occurred a series of plate subduction, collision, assembly, rifting and break...The western margin of Yangtze block and southwestern Sanjiang region absorbed much attention from geologists. It has been proved that there occurred a series of plate subduction, collision, assembly, rifting and breakup processes between them since Palaeozoic and the tectonic evolutionary relationship between them is clear. But in Proterozoic this kind of links between them became unclear. Did they undergo the assembly and breakup processes of the Rodinia super continent? This paper will take a primary discussion on this question on the basis of basement component, structure characteristics and magmatic activities.1\ Basement features\;(1) In western margin of Yangtze block its basement is composed of crystalline basement and folded basement, a so\|called double\|layer structure. The crystalline basement is made up of Kangding group, Pudeng Formation and Dibadu Formation, among them Kangding group is a representative and composed mainly of migmatite, compositing gneiss, hornblende schist and granulitite. The isotopic age of crystalline basement is older than 1900Ma, so its geological time is late Archaean to early Proterozoic. The folded basement is composed of Dahongshan group, Hekou group, Kunyang group, Huili group and Yanbian group. Their rock associations are made up mainly of spilite\|keratophyre formation, carbonate formation, clastic rock and clastic rock formation with some basic volcanic rocks. The folded basement is assigned to be early and middle Proterozoic (1000～1700M a).展开更多
扬子板块的太古宙-古元古代基底出露十分有限,制约了对扬子早前寒武纪地质演化的认识。本次研究对扬子板块西南缘撮科地区的大红山群和昆阳群变沉积岩开展了碎屑锆石原位U-Pb年龄、Hf-O同位素及微量元素研究。测年结果显示,大红山群谐...扬子板块的太古宙-古元古代基底出露十分有限,制约了对扬子早前寒武纪地质演化的认识。本次研究对扬子板块西南缘撮科地区的大红山群和昆阳群变沉积岩开展了碎屑锆石原位U-Pb年龄、Hf-O同位素及微量元素研究。测年结果显示,大红山群谐和锆石年龄分布于3092~1786Ma之间,最年轻碎屑锆石年龄为1786Ma,限定大红山群最大沉积时代为古元古代晚期。昆阳群谐和锆石年龄分布于2874~1031Ma之间,最年轻碎屑锆石年龄为1031Ma,表明昆阳群最大沉积时代为中元古代晚期。除少量较年轻锆石(<1.75Ga)外,昆阳群和大红山群具有相似的年龄分布特征,两个主要的年龄峰为2.0~1.85Ga和2.4~2.2Ga。尽管古元古代碎屑锆石的年龄峰与撮科地区已报道的古元古代岩浆活动期次一致,但仅有少部分碎屑锆石的Hf-O同位素特征与撮科古元古代岩浆岩相似,大多数碎屑锆石Hf-O同位素组成与加拿大Rae克拉通古元古代变沉积岩中碎屑锆石相似,暗示古元古代碎屑物质可能仅少部分来自撮科地区已识别的古元古代岩浆岩,而大部分可能来自与Rae克拉通发育的古元古岩浆岩相似的源区。大红山群和昆阳群中1.9~1.03Ga的碎屑锆石可能来自扬子西南缘发育的古元古代晚期-中元古代晚期岩浆岩。结合前人的资料,我们认为我国撮科和越南北部的Phan Si Pan带经历了与加拿大Rae克拉通相似的古元古代演化过程,支持2.4~2.3Ga扬子西南缘卷入Arrowsmith造山事件,并与Rae克拉通一起参与哥伦比亚超大陆聚合过程的认识。展开更多
文摘The western margin of Yangtze block and southwestern Sanjiang region absorbed much attention from geologists. It has been proved that there occurred a series of plate subduction, collision, assembly, rifting and breakup processes between them since Palaeozoic and the tectonic evolutionary relationship between them is clear. But in Proterozoic this kind of links between them became unclear. Did they undergo the assembly and breakup processes of the Rodinia super continent? This paper will take a primary discussion on this question on the basis of basement component, structure characteristics and magmatic activities.1\ Basement features\;(1) In western margin of Yangtze block its basement is composed of crystalline basement and folded basement, a so\|called double\|layer structure. The crystalline basement is made up of Kangding group, Pudeng Formation and Dibadu Formation, among them Kangding group is a representative and composed mainly of migmatite, compositing gneiss, hornblende schist and granulitite. The isotopic age of crystalline basement is older than 1900Ma, so its geological time is late Archaean to early Proterozoic. The folded basement is composed of Dahongshan group, Hekou group, Kunyang group, Huili group and Yanbian group. Their rock associations are made up mainly of spilite\|keratophyre formation, carbonate formation, clastic rock and clastic rock formation with some basic volcanic rocks. The folded basement is assigned to be early and middle Proterozoic (1000～1700M a).
文摘扬子板块的太古宙-古元古代基底出露十分有限,制约了对扬子早前寒武纪地质演化的认识。本次研究对扬子板块西南缘撮科地区的大红山群和昆阳群变沉积岩开展了碎屑锆石原位U-Pb年龄、Hf-O同位素及微量元素研究。测年结果显示,大红山群谐和锆石年龄分布于3092~1786Ma之间,最年轻碎屑锆石年龄为1786Ma,限定大红山群最大沉积时代为古元古代晚期。昆阳群谐和锆石年龄分布于2874~1031Ma之间,最年轻碎屑锆石年龄为1031Ma,表明昆阳群最大沉积时代为中元古代晚期。除少量较年轻锆石(<1.75Ga)外,昆阳群和大红山群具有相似的年龄分布特征,两个主要的年龄峰为2.0~1.85Ga和2.4~2.2Ga。尽管古元古代碎屑锆石的年龄峰与撮科地区已报道的古元古代岩浆活动期次一致,但仅有少部分碎屑锆石的Hf-O同位素特征与撮科古元古代岩浆岩相似,大多数碎屑锆石Hf-O同位素组成与加拿大Rae克拉通古元古代变沉积岩中碎屑锆石相似,暗示古元古代碎屑物质可能仅少部分来自撮科地区已识别的古元古代岩浆岩,而大部分可能来自与Rae克拉通发育的古元古岩浆岩相似的源区。大红山群和昆阳群中1.9~1.03Ga的碎屑锆石可能来自扬子西南缘发育的古元古代晚期-中元古代晚期岩浆岩。结合前人的资料,我们认为我国撮科和越南北部的Phan Si Pan带经历了与加拿大Rae克拉通相似的古元古代演化过程,支持2.4~2.3Ga扬子西南缘卷入Arrowsmith造山事件,并与Rae克拉通一起参与哥伦比亚超大陆聚合过程的认识。
