Characteristics and origin of sepiolite (Meerschaum) from Central Somalia
Characteristics and origin of sepiolite (Meerschaum) from Central Somalia
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DOI：
10.1180/000985598545525
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发表时间：
1998-06
期刊：
影响因子：
1.5
通讯作者：
A. Singer;K. Stahr;M. Zarei
中科院分区：
文献类型：
--
作者：
A. Singer;K. Stahr;M. Zarei
索马里中部高原地区埃尔布尔附近的一个干盐湖状洼地中产出近纯的海泡石粘土。该存款与下至中始新世Taleh地层有关，该地层除石灰岩、白云石和含石膏泥灰岩外，还包括大量硬石膏和各种硬石膏，主要是石膏。采用XRD、DTA、IR、EM等手段对材料进行了表征。XRD和DTA分析表明，从40 cm到300 cm深度，材料由结晶良好的海泡石组成，在某些层中伴有少量方解石和痕量石英和岩盐。X射线荧光光谱测定的化学成分表明是一种低铁矿物，分子式为：（Si11.888Al0.112）（Mg7.313Al0.154Fe0.084）O30（OH）4（OH 2）4 ·x8 H2O。以交织垫的形式排列的纤维是直的，并且具有在2-6 μm之间变化的长度和20-40 nm的宽度。通常，它们聚集成两个平行排列的纤维单元，彼此具有随机取向，形成致密的孔隙网络。与西班牙Vallecas海泡石相比，该材料的高粘度和外表面积（306-346 m2 g-1）表明该粘土具有很高的工业适用性。存款的范围尚不清楚。岩性、地貌特征表明该存款形成于湖泊封闭盆地蒸发环境。与西班牙和土耳其海泡石矿床形成的古湖泊环境相反，El Bur海泡石显然是较新的。
Abstract Nearly pure sepiolite clay crops out in a playa-like depression near El Bur, Central Plateau region of Somalia. The deposit is associated with the Lower to Mid-Eocene Taleh Formation that includes, besides limestone, dolomite and gypsiferous marls, extensive anhydrite and various evaporites, primarily gypsum. The material was examined by XRD, DTA, IR and EM. The XRD and DTA analyses indicated that from 40 cm down to a depth of 300 cm, the material consists of well- crystallized sepiolite, accompanied in some layers by minor calcite and traces of quartz and halite. The chemical composition, determined by XRF, indicated a low-Fe mineral, with the formula: (Si11.888Al0.112)(Mg7.313Al0.154Fe0.084)O30(OH)4(OH2)4 · x8H2O. The fibres, arranged in the form of interwoven mats, are straight and have lengths varying between 2-6 μm and widths of 20-40 nm. Commonly, they are aggregated into units of two parallel-lying fibres, with a random orientation against each other, creating a dense network of pores. The high viscosity and external surface area (306-346 m2g-1) of the material, compared to those of the Spanish Vallecas sepiolite, suggest the high industrial suitability of this clay. The extent of the deposit is not known. Lithology and geomorphology indicate a lacustrine, closed basin evaporative environment of formation for this deposit. In contrast to the palaeolacustrine environments of formation of Spanish and Turkish sepiolite deposits, the El Bur sepiolite apparently is more recent.