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Geological, mineralogical and geochemical characteristics of Mississippian K-bentonites from southern Turkey: A correlation with coeval tephras from Gondwana-derived terranes
Journal of African Earth Sciences ( IF 2.2 ) Pub Date : 2021-05-14 , DOI: 10.1016/j.jafrearsci.2021.104258
Ömer Bozkaya , Asuman Günal-Türkmenoğlu , Mehmet Cemal Göncüoğlu , Cengiz Okuyucu

Five thin (5–15 cm) and yellowish green tephra (K-bentonite) layers are exposed along two sections in the south of Akşehir (Konya, southern Turkey) within the Early Carboniferous (Mississippian) red dolomite-dolomitic limestone succession of the Sultandağ Unit in the central Tauride Belt. K-bentonites exhibit typical porphyritic texture with euhedral plagioclase phenocrysts replaced by fine-grained white K-micas and sparry dolomite crystals. The intensively sericitized volcanic matrix has vitrophyric texture and contains hydroxidized euhedral pyrite crystals. Illite is the only clay mineral in all K-bentonite samples. Non-clay minerals are dolomite, calcite, quartz, pyrite, rutile and zircon. Illites have sheet-like flakes (1–4 μm sizes) showing well-developed orientations and partly slaty cleavage. Illite Kübler index values (KI, Δ°2θ) of K-bentonites reflect high-grade diagenetic to anchizonal conditions indicating temperatures that reached up to 200 °C. Illite d060 values (1.4990–1.5007 Å) corresponding to dioctahedral composition display differences in coexisting slates and shales of the same age. Illite polytypes are characterized by the association of 2M1, 1M and 1Md. The presence of 1M illites is indicative of a volcanic (tephra) origin. Immobile element compositions suggest that tephras have been derived from trachyandesitic volcanism. K-bentonites exhibit some differences from the coeval pelitic occurrences in the Hadim-Bozkır areas, S Turkey, and the Late Devonian-Early Carboniferous K-bentonites in Bartın and Zonguldak areas of the Istanbul-Zonguldak Terrane, NW Turkey. A geochemical evolution of the studied K-bentonites suggests that they were possibly originated from the Early Carboniferous (Mississippian) intra-continental back-arc magmatism at the northern margin of Gondwana-derived Tauride-Anatolide microplate.



中文翻译:

来自土耳其南部的密西西比州钾膨润土的地质,矿物学和地球化学特征:与冈瓦纳衍生的地脉的古代特非拉斯的相关性

在苏丹国的早期石炭纪(密西西比州)红色白云岩-白云岩灰岩岩层中,阿克谢希尔(土耳其南部,科尼亚)南部的两个部分暴露了五个薄层(5–15厘米)和淡黄色的绿色辉石(K-膨润土)层。单位位于陶瑞德中央带。K膨润土表现出典型的斑状质构,带有正板斜长石面晶石,被细颗粒的白色K-米加斯和斯帕里白云石晶体所取代。强烈浆化的火山岩基质具有玻璃质的质构,并含有水合氧化的黄铁矿黄铁矿晶体。伊利石是所有钾膨润土样品中唯一的粘土矿物。非粘土矿物是白云石,方解石,石英,黄铁矿,金红石和锆石。Illite的薄片状薄片(大小为1-4μm)显示出良好的取向,部分呈片状分裂。钾基膨润土的伊利石库伯勒指数值(KI,Δ°2θ)反映了从成岩到顺层的高级成岩条件,表明温度高达200°C。伊利石ð060对应于共存石板和相同年龄的页岩双八面体组合物显示差的值(1.4990-1.5007)。伊利石多型体通过的2关联特征中号1,1中号和1中号d。1M的存在伊利石是火山爆发的标志。不可移动的元素组成表明,特弗拉斯是由trachyandesitic火山活动衍生而来的。钾膨润土与土耳其南部Hadim-Bozkır地区的中世纪古胶质岩以及在土耳其西北部伊斯坦布尔-宗古达克地貌的Bartın和Zonguldak地区晚泥盆世-早期石炭纪钾膨润土表现出一些差异。所研究的钾膨润土的地球化学演变表明,它们可能起源于冈瓦纳派生的牛磺酸-阿那托利德微板块北缘的早期石炭纪(密西西比州)陆内弧后岩浆作用

更新日期:2021-05-19
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