GEHLENITE FROM THREE OCCURRENCES OF HIGH-TEMPERATURE SKARNS, ROMANIA: NEW MINERALOGICAL DATA
GEHLENITE FROM THREE OCCURRENCES OF HIGH-TEMPERATURE SKARNS, ROMANIA: NEW MINERALOGICAL DATA
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DOI：
10.3749/canmin.49.4.1001
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发表时间：
2011-08-01
影响因子：
0.9
通讯作者：
Rondeaux, Melanie
中科院分区：
文献类型：
--
作者：
Marincea, Stefan;Dumitras, Delia-Georgeta;Rondeaux, Melanie
钙黄长石是罗马尼亚三个高温钙夕卡岩中的常见矿物：Apuseni山脉的Magureaua Vatei和Cornet Hill以及Banat的Oravita。在所有三个矿点中，钙黄长石带出现在上白垩纪闪长质或二长闪长质岩体与中生代碳质层序之间的接触面内。黄长石固溶体在Oravita、Magureaua Vatei和Cornet Hill分别为Ak（34.1）-Ak（51.2）（平均Ak（41.2））、Ak（30.4）-Ak（42.9）（平均Ak（38.3））和Ak（24.3）-Ak（41.7）（平均Ak（32.9））。“Na-黄长石”含量低，最高可达1.96摩尔%，在Cornet Hill，最高可达3.60 mol.%在奥拉维塔在Oravita，晶胞参数a的范围为7.679（3）至7.734（3）埃，在Magureaua Vatei为7.683（4）至7.735（1）埃，在Cornet Hill为7.684（3）至7.733（1）埃，而在Oravita，c的范围为5.043（3）至5.065（3）埃，Magureaua Vatei为5.040（1）至5.070（3）埃，Cornet Hill为5.044（1）至5.067（4）埃。仅考虑镁黄长石取代不可能量化晶体学参数的变化，因为“Na-黄长石”和“Fe-镁黄长石”取代也起重要作用。的细胞参数a几乎保持恒定的实验误差内，尽管增加的镁黄长石的钙黄长石取代，由于相反的影响，“钠黄长石”组件。镁黄长石取代在增加晶胞体积方面优于“Na-黄长石”的相反影响，并且在降低晶胞参数c方面与“Na-黄长石”的影响相加。红外吸收光谱中分别位于855 cm（-1）和670 cm（-1）附近的谱带记录（可暂时归属于Al-O-Al拉伸）表明，在所有三个矿点中均存在黄长石组中富含钙铝黄长石的成员。
Gehlenite is a common mineral in three high-temperature calcic skarns in Romania: Magureaua Vatei and Cornet Hill in Apuseni Mountains and Oravita in Banat. In all three occurrences, a gehlenite zone occurs within the contact between dioritic or monzodioritic bodies of Upper Cretaceous age and carbonaceous sequences of Mesozoic age. The melilite solid-solutions vary from Ak(34.1) to Ak(51.2) (mean Ak(41.2)) at Oravita, from Ak(30.4) to Ak(42.9) (mean Ak(38.3)) at Magureaua Vatei, and from Ak(24.3) to Ak(41.7) (mean Ak(32.9)) at Cornet Hill, respectively. The content of "Na-melilite" is low, from up to 1.96 mol.% at Cornet Hill to up to 3.60 mol.% at Oravita. The cell parameter a ranges from 7.679(3) to 7.734(3) angstrom at Oravita, from 7.683(4) to 7.735(1) angstrom at Magureaua Vatei, and from 7.684(3) to 7.733(1) angstrom at Cornet Hill, whereas c varies from 5.043(3) to 5.065(3) angstrom at Oravita, from 5.040(1) to 5.070(3) angstrom at Magureaua Vatei, and from 5.044(1) to 5.067(4) angstrom at Cornet Hill. It is not possible to quantify the variations in the crystallographic parameters by considering only the akermanitic substitution because the "Na-melilite" and "Fe-akermanite" substitutions also play an important role. The cell parameter a remains practically constant within experimental errors, in spite of the increasing akermanite-for-gehlenite substitution, due to the opposite influence of the "Na-melilite" component. The akermanite substitution prevails over the opposite influence of "Na-melilite" in increasing the cell volume, and is additive to the influence of "Na-melilite" in decreasing the cell parameter c. The record in the infrared-absorption spectra of bands located at similar to 855 cm(-1) and similar to 670 cm(-1), respectively, which may be tentatively assigned to Al-O-Al stretching, is indicative of the presence of gehlenite-rich members of the melilite group in all the three occurrences.