Petrography and mineral chemistry of the Varena Iron Ore deposit, southeastern Lithuania: implications for the evolution of carbonate and silicate rocks and ore mineralization

IF 0.5 4区地球科学 Q4 GEOLOGY

Baltica Pub Date : 2019-08-01 DOI:10.5200/BALTICA.2019.1.9

G. Skridlaitė, L. Siliauskas, S. Prušinskienė, B. Bagiński

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引用次数: 4

Abstract

The large Varena Iron Ore deposit of southeast Lithuania lies beneath 200–400 m thick sedimentary cover in the East European Craton. Several drilling projects have revealed that it contains ca. 70–200 million tons of iron ore. A metasomatic origin has been proposed by several investigators, with an igneous (mafic, ultramafic carbonatitic) origin also considered. Detailed micropetrography on a variety of ore-bearing and skarnitised samples through backscattered electron imaging, along with mineral chemical analysis and monazite dating by electron microprobe, provide support for a metasomatic origin. High-grade temperature (ca. 700–750° C) skarns containing forsterite, enstatite, spinel and diopside were formed preferentially in carbonate-rich rocks and were subsequently overprinted by amphibole-bearing (tremolite, actinolite, anthophyllite and hornblende) skarns. A low-temperature hydrous influx and changing redox conditions not only caused the serpentinization of the earlier skarns, but also deposited a considerable amount of iron ore in the form of magnetite. Iron was derived from various sources and was accompanied by sulphide, apatite, REE and other mineralizations. The ca. 1.78 Ga monazite grew during the regional metamorphism, while ca. 1.54 Ga is attributed to the last mineralization phases.

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立陶宛东南部瓦雷纳铁矿床的岩石学和矿物化学:对碳酸盐和硅酸盐岩石演化和矿化的影响

立陶宛东南部的大型瓦雷纳铁矿床位于东欧克拉通200–400米厚的沉积盖层之下。几个钻探项目表明，它含有约7000万至2亿吨铁矿石。一些研究人员提出了交代成因，还考虑了火成岩（镁铁质、超镁铁质碳酸盐岩）成因。通过背散射电子成像对各种含矿和矽卡岩样品进行详细的微地质成像，以及通过电子探针进行矿物化学分析和独居石定年，为交代成因提供了支持。含有镁橄榄石、顽火辉石、尖晶石和透辉石的高品位温度（约700–750°C）矽卡岩优先形成于富含碳酸盐的岩石中，随后被含角闪石（透闪石、阳起石、直闪石和角闪石）的矽卡岩叠加。低温含水流入和氧化还原条件的变化不仅导致了早期矽卡岩的蛇纹石化，还以磁铁矿的形式沉积了大量铁矿石。铁的来源多种多样，并伴有硫化物、磷灰石、稀土元素和其他矿化作用。约1.78 Ga独居石在区域变质作用期间生长，而约1.54 Ga则归因于最后的矿化阶段。

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来源期刊

Baltica 地学-地质学

CiteScore

1.30

自引率

14.30%

发文量

审稿时长

>12 weeks

期刊介绍： BALTICA is an international periodical journal on Earth sciences devoted to the Baltic countries region and the Baltic Sea problems. This edition as a Yearbook is established in 1961 by initiative of Academician Vytautas Gudelis. Since 1993, an Editor-in-Chief of the journal became Academician Algimantas Grigelis. BALTICA is published biannually (in June and December) in cooperation with geoscientists of the circum-Baltic States. BALTICA is publishing original peer-reviewed papers of international interests on various Earth sciences issues. The particular emphasis is given to Quaternary geology, climate changes and development of ecosystems, palaeogeography, environmental geology, as well as stratigraphy, tectonics, sedimentology and surface processes with relevance to the geological history of the Baltic Sea and land areas. Journal emphasizes modern techniques, methodology and standards. The journal structure comprises original articles, short reviews, information, bibliography.