粤北黄岗镇侧塘早志留世具似大陆弧特征S型花岗岩成因及地质意义
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引用本文:黄孔文,郭敏,汤珂,林杰春,胡启锋,王邱春.2021.粤北黄岗镇侧塘早志留世具似大陆弧特征S型花岗岩成因及地质意义[J].地球学报,42(4):487-500.
DOI:10.3975/cagsb.2020.120601
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作者单位E-mail
黄孔文 广东省地质调查院 huangkongwen0466@163.com 
郭敏 广东省地质调查院  
汤珂 广东省地质调查院  
林杰春 广东省地质调查院  
胡启锋 广东省地质调查院  
王邱春 广东省地质调查院  
基金项目:中国地质调查局地质调查项目(编号: DD20160032-17)
中文摘要:研究区位于武夷—云开陆内造山带上。侧塘岩体岩性主要是片麻状中细粒斑状黑云母二长花岗岩。LA-ICP-MS锆石U-Pb锆石加权平均年龄为(441.5±13) Ma, 表明片麻状花岗岩侵位时代为早志留世。岩体K2O/Na2O大于1.1(K2O/Na2O= 1.10 ~3.52, 个别为22.38), 铝饱和指数(A/CNK)为1.26~3.49, 属高钾钙碱性强过铝花岗岩。岩石总体上富集Rb、Th、U、K、Pb、Nd等, 亏损Ba、Nb、Ta、Sr、Ti等, 明显富集轻稀土元素[(La/Yb)N=5.18~10.62], 具有较强的负Eu异常δEu =0.52~0.60), 具似大陆弧特征。锆石Hf同位素研究结果表明, εHf(t)= –1.3~ –12.5, 其平均值为–5.82。两阶段模式年龄(TDM2)主要为1502~2228 Ma (n=10), 平均值为1 794.8 Ma。这些地球化学特征指示片麻状花岗岩为S型花岗岩。武夷—云开陆内造山早期挤压造山造成强烈褶皱和逆冲推覆, 导致地壳加厚, 并诱发下地壳古—中元古代砂泥质麻粒岩相源岩发生部分熔融而形成侧塘岩体。
中文关键词:侧塘岩体  LA-ICP-MS锆石U-Pb  Hf同位素  S型花岗岩
 
The Origin of the Early Silurian S-type Cetang Granite with the Continental Arc-like Feature from Huanggang Town in Northern Guangdong Province and Its Geological Significance
Abstract:The studied rock mass is located in the Wuyi–Yunkai orogenic belt, and its main rock is the gneissic granodioritic porphyry, indicating that the rock mass was formed in Early Silurian. The weighted average age of the zircon ages is (441.5±13) Ma. The K2O/Na2O ratios are higher than 1 (K2O/Na2O=1.10 ~ 4.50), with A/CNK ratios being 1.26~3.49, suggesting high potassium calc-alkaline strongly peraluminous series. The enrichment of Ba, Rb, Th and P, depletion of U, Pb, K, Sr and Ti, obvious enrichment of REE [(La/Yb)N=5.18~10.62], and obvious depletion of Eu (δEu =0.52~0.74) suggest the continental arc-like feature and indicate that the gneissic granodioritic porphyry in Cetang belongs to S type granite. The zircon Hf isotopic data indicate that the εHf(t) values are between –1.3 and –12.5, all less than 0, averaging –5.82. The zircon two-stage Hf model ages (TDM2) range from 1502 Ma to 2228 Ma (n=10), with their average age being 1 794.8 Ma. These characteristics indicate that the the gneissic middle-fine grained biotite adamellite is S type granite. The Cetang rock mass was formed as follows: The early intra-continent orogeny extrusion in the Wuyi–Yunkai orogen belt included fold and thrust nappe, which led to thickened crust and triggered partial melting of the Palaeoproterozoic–Mesoproterozoic sandy – greywacke granulite facies source from the lower crust.
keywords:Cetang rock mass  LA-ICP-MS zircon U-Pb dating  Hf isotopic  S-type granite
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