Sr,Nd,Pb isotopic characteristics of granite in Jinduicheng area and their geological significance
Sr,Nd,Pb isotopic characteristics of granite in Jinduicheng area and their geological significance
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发表时间：
2011
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通讯作者：
L. Hong;Mlr Key
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作者：
L. Hong;Mlr Key
岩石学和元素地球化学研究表明，金堆城矿集区金堆城花岗斑岩和八里坡花岗斑岩均为I型花岗岩。金堆城斑岩体SiO2值变化范围为72.89%~74.06%（平均73.48%），MgO值为0.073%~0.30%，ΣREE值为稀土元素含量为43.29%~93.94%,呈“V”型分布,存在明显的负Eu异常和弱的负Ce异常,δEu值为0.43~0.78,δCe为0.74~0.86。 69.87～70.80%，Al2O3值为14.93%～15.46%，MgO为0.28%～0.48%，岩石稀土元素总浓度(ΣREE)为125.23～139.63×10-6，Sr/Y比值普遍高于60，Eu无异常或弱正异常，Ce呈弱负异常,存在HFSE(Ba、U、K等)富集,P、Ta、Sr贫化。通过绘制花岗斑岩铅同位素在207Pb/204Pb图及208Pb/204Pb与206Pb/204Pb演化曲线上的结果表明,八里坡花岗斑岩的铅可能来自于壳源区,金堆城花岗斑岩的铅可能来源于壳幔混合源区。金堆城具有低Nd(e(Nd,t)=-20.8~-18.3)和高Sr(e(Sr,t)=63.0~74.3)，八里坡岩石的e(Nd,t)极低为-20.8~-18.3，e(Sr,t)相对较高。 63.0~74.3.Sr.Nd、Pb图显示金堆城岩石起源于下地壳,但受到幔源物质的污染,而八里坡烃源岩为下地壳,具有相当大的成矿潜力。Sr、Nd、Pb同位素值与华北板块数据相近,表明这些侵入体构成了华北板块的组成部分。
A study of petrology and element geochemistry shows that Jinduicheng granite porphyry and Balipo granite porphyry are I–type granites in the Jinduicheng ore concentration area.SiO2 values of Jinduicheng porphyry bodies vary in the range of 72.89%~74.06%(73.48% on average),MgO values are 0.073%~0.30%,∑REE values are 43.29%~93.94%,REE distribution patterns are of "V" type,there exists an evident negative Eu anomaly and a weak negative Ce anomaly,δEu values are 0.43~0.78,and δCe are 0.74~0.86.They are enriched with K,Rb,U,Th and Sr,and strongly depleted in Ba,P and Ti.SiO2 of Balipo granites range from 69.87 to 70.80%,Al2O3 values are 14.93%~15.46%,MgO are 0.28%~0.48%,the total rare earth element concentrations(∑REE) of the rocks are 125.23~139.63×10-6,the ratios of Sr/Y are generally higher than 60,Eu has no anomaly or weak positive anomaly,Ce shows weak negative anomaly,and there exists the enrichment of HFSE(such as Ba,U and K) and the depletion of P,Ta and Sr.Plotting of lead isotopes of granite porphyry on the 207Pb/204Pb diagrams and 208Pb/204Pb versus 206Pb/204Pb evolution curves show that lead of Balipo granite porphyry might have come from crust source area,and lead of Jinduicheng granite porphyry was probably derived from the crust-mantle mixing source area.Jinduicheng has low Nd(e(Nd,t)=-20.8~-18.3) and high Sr(e(Sr,t)= 63.0~74.3),Balipo rocks have extremely low e(Nd,t) of-20.8~-18.3 and relatively high e(Sr,t) of 63.0~74.3.Sr.Nd and Pb plots show that the Jinduicheng rocks originated from the lower crust,but were contaminated by mantle-derived materials,and the source rock of Balipo is the lower crust,which has considerable ore-forming potential.the values of Sr,Nd and Pb isotopes are similar to the data of the North China plate,suggesting that these intrusives constitute a component part of the North China plate.