摘要
在中生代岩浆作用过程主量元素、微量元素和Sr-Nd同位素地球化学演化轨迹的研究基础上,探讨了新路盆地火山岩型铀成矿的深部动力学机制。研究表明,新路盆地由早至晚系列岩浆岩,SiO2含量依次降低,碱度和K2O/Na2O比值逐渐升高,氧化物含量表现为"跳跃性"演变并趋向辉绿岩;ΣLREE、δEu值和Sr元素等含量显著动态升高;微量元素特征比值表现出趋势性变化特点;Sr-Nd同位素演化呈现出由黄尖组熔结凝灰岩依次趋向花岗斑岩、辉绿岩的混合演化趋势线;代表成矿流体同位素组成的萤石投影点位于岩浆作用过程Sr-Nd同位素混合演化趋势线上,且较花岗斑岩更趋近于辉绿岩投影区。认为新路盆地铀矿床成矿流体具有壳幔源区物质混合特征;酸性系列岩浆岩与火山岩型铀矿在空间上的叠置,是壳幔作用机制下系列产物的耦合;来自岩石圈富集地幔的以富含LREE及K、Sr等大离子亲石元素为特征的高温"轻物质流"持续上涌及由此诱发的壳幔作用,为新路盆地岩浆活动及火山岩型铀成矿作用提供了动力学机制;壳幔作用源区是铀成矿作用的动力源,也是成矿流体的发源地。
Based on analysis of the geochemical evolution of major and trace elements, and Sr-Nd isotopes of Mesozoic magmatism in the Xinlu basin, this study discussed the deep geodynamie mechanism of the volcanic -type uranium mineralization. Geochemical study shows that magmatic rocks formed from early to late periods in the basin are characterized by decreasing of SiO2 contents, increasing of alkalinity and K2 O/ Na20 ratios, oxide contents （turning into diabase）, （LREE, ∞Eu and Sr, and tendency change of trace elements. The evolution of Sr-Nd isotope presents a mixed trend line changing in order from Huangjian Formation ignimbrite to granite-porphyry to diabase. Fluorite representing the isotopic compositions of ore-forming fluids is projected on the mixed evolution trend line, nearer to the projection zone of diabase than granite-porphyry. It is suggested that the ore-forming fluids of the uranium deposit was of mixing features of crust and mantle sources and spatial superimposition between acidic magmatic rock and volcanic rock was the result of the Mesozoic crust-mantle interaction. Continuous upwelling of the high temperature ＂light material flow＂ that came from enriched mantle （enriched in LREE, K, Sr, etc） and its inducing crust-mantle effect provided geodynamics for magmatic activity and uranium mineralization in Xinlu basin. Therefore, the crust-mantle interaction is not only the source for driving force but the source of ore forming fluids.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2013年第5期703-714,共12页
Acta Geologica Sinica
基金
国家自然科学基金(批准号:41040019)资助的成果
关键词
壳幔作用
岩浆作用
“轻物质流”上涌
火山岩型铀矿
浙江新路盆地
crust-mantle interaction^magmatism
upwelling of the ＂light material flow＂
volcanic-typeduranium deposit
Xinlu Basin, Zhejiang
