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首页> 外文期刊>International Journal of Earth Sciences >Geochemical and isotopic constraints on the role of juvenile crust and magma mixing in the UDMA magmatism, Iran: evidence from mafic microgranular enclaves and cogenetic granitoids in the Zafarghand igneous complex
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Geochemical and isotopic constraints on the role of juvenile crust and magma mixing in the UDMA magmatism, Iran: evidence from mafic microgranular enclaves and cogenetic granitoids in the Zafarghand igneous complex

机译：伊朗UDMA岩浆作用中地壳和岩浆混合作用的地球化学和同位素约束：Zafarghand火成岩复合体中的镁铁质微颗粒飞地和共生花岗岩类的证据

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Abstract The Zafarghand Igneous Complex is composed of granite, granodiorite, diorite, and gabbro that contain many mafic microgranular enclaves. This complex was emplaced during the late Oligocene (24.6 Ma) to form part of the Urumieh–Dokhtar magmatic arc of Central Iran. The enclaves have spheroidal to elongated/lenticular shapes and are quenched mafic melts in felsic host magma as evidenced by fine-grained sinuous margins and (or) locally transitional and diffuse contacts with the host rocks, as well as having disequilibrium textures. These textures including oscillatory zoning with resorption surfaces on plagioclase, feldspar megacrysts with poikilitic and anti-rapakivi textures, mafic clots, acicular apatites, and small lath-shaped plagioclase in larger plagioclase crystals all indicate that the enclaves crystallized from mafic magma that was injected into and mixing/mingling with the host felsic magma. The studied rocks have calc-alkaline, metaluminous compositions, with an arc affinity. They are enriched in large ion lithophile elements, light rare-earth elements, and depleted in high field strength elements with significant negative Eu anomalies. The Sr–Nd isotopic data for all of the samples are similar and display ISr = 0.705123–0.705950 and εNd (24.6 Ma) = − 1.04–1.03 with TDM ~ 0.9–1.1 Ga. The host granites and enclaves are of mixed/mingled origin and most probably formed by the interaction between the juvenile lower crust with a basaltic composition and old lower or middle continental crust as a major component and lithospheric mantle as a minor component; this was followed by fractional crystallization and possibly minor crustal assimilation. The source seems to be comprised of about 90–80% of the basaltic magma and about 10–20% of lower/middle-crust-derived magma. Geochemical characteristics indicate that the intrusion of these rocks from a subduction zone setting below the Central Iran micro-continent was related to an active continental margin, although was transitional to a transtensional setting possibly due oblique convergence to slab rollback or break-off.
机译：摘要Zafarghand火成岩复合体由花岗岩，花岗闪长岩，闪长岩和辉长岩组成，其中包含许多镁铁质微细颗粒飞地。这个复合体是在渐新世晚期（24.6 Ma）形成的，构成了伊朗中部Urumieh–Dokhtar岩浆弧的一部分。这些飞地具有球形到拉长/双凸的形状，并且是长石质岩浆中淬灭的镁铁质熔体，其特征是细密的蜿蜒边缘和（或）与基质岩的局部过渡和扩散接触，以及具有不平衡的质地。这些纹理包括斜长石上具有吸收表面的振荡带，具有斜长石和反rapakivi质地的长石巨晶，镁铁凝块，针状磷灰石以及较大斜长石晶体中的小板条状斜长石，这些都表明从镁铁质岩浆中结晶出的飞地已注入并与长英质岩浆混合/混合。所研究的岩石具有钙碱金属元素，具有电弧亲和力。它们富含大型的离子亲石元素，轻稀土元素，并且贫化了具有显着负Eu异常的高场强元素。所有样品的Sr-Nd同位素数据相似，显示为ISr = 0.705123-0.705950和εNd（24.6Ma）=-1.04-1.03，TDM〜0.9-1.1Ga。宿主花岗岩和飞地是混合/混合的最有可能是由具有玄武质组成的下部下地壳与作为主要成分的旧的下部或中部大陆壳以及作为次要成分的岩石圈地幔之间的相互作用形成的；随后是部分结晶，可能还有次要的地壳同化作用。来源似乎由玄武岩浆的约90％至80％和下/中地壳岩浆的约10％至20％组成。地球化学特征表明，这些岩石从伊朗中部微大陆以下的俯冲带侵入与活跃的大陆边缘有关，尽管过渡至张拉带可能是由于板块向后倾斜或折断的倾斜收敛所致。

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