A-type volcanic–intrusive complex in the Huanggangshan Basin: Implications for early cretaceous crust–mantle interaction in the Gan-Hang Belt and adjacent areas, South China
A-type volcanic–intrusive complex in the Huanggangshan Basin: Implications for early cretaceous crust–mantle interaction in the Gan-Hang Belt and adjacent areas, South China
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DOI：
10.1016/j.lithos.2019.01.021
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发表时间：
2019-07
期刊：
影响因子：
3.5
通讯作者：
Hui-Qing Huang;Kai‐Xing Wang;Jiayong Pan;Xiao-dong Liu;Yue Sun
中科院分区：
文献类型：
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作者：
Hui-Qing Huang;Kai‐Xing Wang;Jiayong Pan;Xiao-dong Liu;Yue Sun
赣杭带及邻区早白垩世A型火山-侵入杂岩的成因和成因至今仍存在争议。北武夷山黄岗山盆地A型火山-侵入杂岩由正长斑岩、花岗斑岩、花岗岩、凝灰质火山岩和火山碎屑岩组成。对这些岩石进行了年代学、地球化学和同位素分析，以研究它们的时代、岩石成因和华南壳幔相互作用。野外观察表明，该A型火山-侵入杂岩中含有丰富的镁铁质微粒包体。不同岩石类型的锆石U-Pb年龄在136 ~ 128 Ma之间。岩石地球化学特征为A型亲合性，包括高的大离子亲石元素和高场强元素含量、Ga/Al比值和锆石饱和温度。(87Sr/86 Sr）i值从0.702704到0.711298不等，εNd（t）= −10.63到−7.28，εHf（t）= −13.26到−7.70。黄岗山盆地A型火山-侵入杂岩的成因可分为三个阶段：（1）壳源镁铁质岩浆与幔源镁铁质岩浆混合形成的正长质岩浆，（2）正长质岩浆中钙长石+黑云母+钛铁矿的分离结晶作用，形成SiO2<71wt%的A型火成岩;斜长石+钾长石+黑云母+磷灰石+褐帘石+钛铁矿的分离结晶，生成SiO2> 71wt%的A型火成岩。结合前人的研究，我们认为赣杭带及邻区早白垩世A型火成岩可能是壳幔源岩浆混合作用的产物，且壳幔相互作用自西南向东北方向较强烈。这种增加的壳幔相互作用可能是对早白垩世弧后拉张环境的响应，可能是古太平洋板块后滚的结果。
The origin and petrogenesis of Early Cretaceous A-type volcanic–intrusive complexes in the Gan-Hang Belt and adjacent areas of South China remain controversial. An A-type volcanic–intrusive complex in the Huanggangshan Basin of North Wuyi Mountain comprises syenite porphyry, granite porphyry, granite, and tuffaceous volcanic and pyroclastic rocks. These rocks were subjected to geochronological, geochemical, and isotopic analyses in order to investigate their age and petrogenesis, and crust–mantle interactions in South China. Field observations reveal that this A-type volcanic–intrusive complex contains abundant mafic microgranular enclaves. Zircon Usingle bondPb dating of the various rock types yielded ages between 136 and 128 Ma. Geochemically, the rocks have A-type affinities, including high large-ion lithophile and high-field-strength element contents, Ga/Al ratios, and zircon saturation temperatures. (87Sr/86Sr)ivalues vary from 0.702704 to 0.711298, and εNd(t) = −10.63 to −7.28 and εHf(t) = −13.26 to −7.70. Three stages of magmatism are proposed to explain the petrogenesis of the A-type volcanic–intrusive complex in the Huanggangshan Basin: (1) syenitic magmas formed by mingling of crustally derived silicic and mantle-derived mafic magmas; (2) fractional crystallization of anorthitic plagioclase + biotite + ilmenite from the syenitic magmas generated A-type igneous rocks with SiO2< 71 wt%; and (3) fractional crystallization of plagioclase + K-feldspar + biotite + apatite + allanite + ilmenite then generated A-type igneous rocks with SiO2> 71 wt%. Combined with previous studies, we suggest that the Early Cretaceous A-type igneous rocks in the Gan-Hang Belt and adjacent areas might have been generated by crust–mantle-derived magma mixing, and the crust–mantle interaction was more intense from southwest to northeast. This increased crust–mantle interaction may have been a response to the Early Cretaceous back-arc extensional environment, possibly as a result of the rollback of the Paleo-Pacific Plate.