Stalactitic rhodochrosite from the 25 de Mayo and Nueve veins, Capillitas, Catamarca, Argentina: Physical and chemical variations

IF 1.1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
María Florencia, MÁRQUEZ-ZAVALÍA, James R. Craig
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引用次数: 0

Abstract

Capillitas is an epithermal vein-type deposit in Argentina known for its mineralogical diversity, with more than one hundred and twenty described minerals, including five new species, and for the presence of banded and stalactitic rhodochrosite. Stalactites occur as single or combined cylinders of different sizes, from a few cm to 1.36 m in length and diameters up to 8 cm. Their cross-sections may show diverse aspects: from simple concentric banding to more intricate textures, whereas their external surface can be smooth, with undulations or with a poker-chip-like texture. The color of the stalactites varies from white to raspberry pink, with occasional brown bands toward the edges corresponding to a variety of rhodochrosite called “capillitite”. The contents of MnO range from 27.50 to 61.71 wt. % as it may be significantly replaced by CaO, FeO, ZnO and MgO. Replacements are reflected in the various shades of pink and brown displayed by this mineral. The different substitutions in the pink specimens exert only a minor influence on the unit cell parameters, whereas, in the brown variety, their size is significantly smaller with average values for pink rhodochrosite ( n = 24): a 4.776 Å, c 15.690 Å and a cell volume of 310.3 Å 3 , whereas, “capillitite” unit-cell parameters ( n = 7) are: a = 4.739, c = 15.558 with a unit-cell volume of 302.6 Å 3 . Conditions of formation of the banded rhodochrosite of the 25 de Mayo vein, obtained from fluid inclusions data, indicate temperatures of 145 ° to 150 °C and salinities of up to 4 wt. % NaCl(eq). The formation of the stalactites is explained by the infiltration of epithermal aqueous liquid, oversa - turated with Mn and bicarbonate, into a transiently vapor-filled, isolated cavity.
阿根廷卡塔马卡卡皮利塔斯5月25日和Nueve矿脉的钟乳石菱铁矿:物理和化学变化
Capillitas是阿根廷的一个浅成热液脉型矿床,以其矿物学多样性而闻名,有超过一百二十种已描述的矿物,包括五个新种,并存在带状和钟乳石菱锰矿。Stalacites以不同尺寸的单个或组合圆柱体出现,长度从几厘米到1.36米,直径可达8厘米。它们的横截面可能表现出不同的方面:从简单的同心条纹到更复杂的纹理,而它们的外表面可以是光滑的,有起伏或扑克芯片状纹理。钟乳石的颜色从白色到覆盆子粉色不等,边缘偶尔会有棕色条纹,对应于一种名为“capillitite”的各种菱锰矿。MnO的含量范围为27.50至61.71重量%,因为它可以被CaO、FeO、ZnO和MgO显著取代。这种矿物所显示的各种深浅的粉红色和棕色反映了置换作用。粉红色样品中的不同取代对晶胞参数的影响很小,而在棕色品种中,它们的大小明显较小,粉红色菱锰矿(n=24)的平均值为:a 4.776Å,c 15.690Å,细胞体积为310.3Å3,而“capillite”晶胞参数(n=7)为:a=4.739,c=15.558,晶胞体积为302.6Å3。从流体包裹体数据中获得的25 de Mayo脉带状菱锰矿的形成条件表明,温度为145°至150°C,盐度高达4 wt.%NaCl(eq)。钟乳石的形成是通过超热液渗透到一个短暂充满蒸汽的孤立空腔中来解释的,超热液中含有Mn和碳酸氢盐。
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来源期刊
Journal of Geosciences
Journal of Geosciences GEOSCIENCES, MULTIDISCIPLINARY-MINERALOGY
CiteScore
2.30
自引率
7.10%
发文量
15
审稿时长
>12 weeks
期刊介绍: The Journal of Geosciences is an international peer-reviewed journal published by the Czech Geological Society with support from the Czech Geological Survey. It accepts high-quality original research or review papers dealing with all aspects of the nature and origin of igneous and metamorphic rocks. The Journal focuses, mainly but not exclusively, on: -Process-oriented regional studies of igneous and metamorphic complexes- Research in structural geology and tectonics- Igneous and metamorphic petrology- Mineral chemistry and mineralogy- Major- and trace-element geochemistry, isotope geochemistry- Dating igneous activity and metamorphic events- Experimental petrology and mineralogy- Theoretical models of igneous and metamorphic processes- Mineralizing processes and mineral deposits. All the papers are written in English, even though they may be accompanied by an additional Czech abstract. Each contribution is a subject to peer review by at least two independent reviewers, typically at least one from abroad. The Journal appears 2 to 4 times a year. Formally it is divided in annual volumes, each of them including 4 issues.
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