Eocene Calc-Alkaline Volcanic Rocks from Central Iran (Southeast of Khur, Isfahan Province); an Evidence of Neotethys Syn-Subduction Magmatism

IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Paniz Shadman, Ghodrat Torabi, Tomoaki Morishita
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引用次数: 0

Abstract

Eocene volcanic rocks with basaltic-trachyandesite and trachybasalt composition which cross-cut the Cretaceous sedimentary rocks, are exposed in the northwestern part of the Central-East Iranian Microcontient (CEIM) (SE of Khur, Isfahan Province, Iran). The rock-forming minerals of these volcanic rocks are olivine (chrysolite and hyalosiderite, Mg# = 0.69–0.71), clinopyroxene (augite with Mg# = 0.74–0.84), orthopyroxene (enstatite with Mg# = 0.61–0.62) and plagioclase (andesine and labradorite with An48.3-65.1). Phenocrysts set in a fine-grained matrix of the same minerals plus sanidine (Or59.1Ab36.6An4.3) with minor amounts of opaque minerals (magnetite and ilmenite). Secondary minerals are chlorite and calcite. The main textures of these volcanic rocks are porphyritic, microlitic porphyritic, poikilitic, and glomeroporphyritic. The Eocene volcanic rocks of the Khur area are characterized by SiO2 content of 51.8 to 54.9 wt %, Al2O3 amounts of 14.35 to 16.47 wt %, and TiO2 values of 0.88 to 0.92 wt %. They exhibit strong enrichment in light rare earth elements (LREE) relative to heavy REE (HREE) (La/Lu ratio up to 102.35), enrichment in large ion lithophile elements (LILEs), depletion in high field strength elements (HFSE), and present negative anomaly in Eu (Eu/Eu* = 0.72–0.87). Chemical characteristics and homogeneity of these volcanic rocks reveal their calc-alkaline nature and suggest that they were derived from a same parental magma and underwent a similar melt extraction. Major and trace elements geochemical features of the analyzed samples indicate that the parental magma was possibly derived from relatively low degrees of partial melting of a mantle wedge spinel lherzolite which was previously enriched by fluids/melts released from the Neo-Tethyan subducted slab.

Abstract Image

伊朗中部(伊斯法罕省Khur东南部)始新世钙碱性火山岩新特提斯同步俯冲岩浆活动的证据
在伊朗中东部微大陆(伊朗伊斯法罕省Khur东南)西北部,暴露出与白垩系沉积岩相交叉的玄武岩-粗面玄武岩和粗面玄武岩组成的始新世火山岩。这些火山岩的造岩矿物为橄榄石(黄璧石和透明黄铁矿,Mg# = 0.69 ~ 0.71)、斜辉石(辉石,Mg# = 0.74 ~ 0.84)、正辉石(顽辉石,Mg# = 0.61 ~ 0.62)和斜长石(安长石和拉长石,Mg# = 48.3 ~ 65.1)。斑晶镶嵌在由相同矿物加水晶石(Or59.1Ab36.6An4.3)和少量不透明矿物(磁铁矿和钛铁矿)组成的细粒基质中。次生矿物为绿泥石和方解石。这些火山岩的主要结构为斑岩、微岩屑斑岩、斑岩和肾小球斑岩。呼尔地区始新世火山岩的SiO2含量为51.8 ~ 54.9 wt %, Al2O3含量为14.35 ~ 16.47 wt %, TiO2含量为0.88 ~ 0.92 wt %。它们表现出轻稀土元素(LREE)相对重稀土元素(HREE)的强富集(La/Lu比值高达102.35),大离子亲石元素(LILEs)富集,高场强元素(HFSE)亏缺,Eu呈负异常(Eu/Eu* = 0.72 ~ 0.87)。这些火山岩的化学特征和均匀性揭示了它们的钙碱性特征,表明它们起源于相同的母岩浆,并经历了相似的熔融提取过程。分析样品的主要元素和微量元素地球化学特征表明,母岩浆可能来源于地幔楔尖晶石橄榄岩相对较低程度的部分熔融,该岩浆先前被新特提斯俯冲板块释放的流体/熔体富集。
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来源期刊
Petrology
Petrology 地学-地球科学综合
CiteScore
2.40
自引率
20.00%
发文量
27
审稿时长
>12 weeks
期刊介绍: Petrology is a journal of magmatic, metamorphic, and experimental petrology, mineralogy, and geochemistry. The journal offers comprehensive information on all multidisciplinary aspects of theoretical, experimental, and applied petrology. By giving special consideration to studies on the petrography of different regions of the former Soviet Union, Petrology provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.
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