Structural controls on cobalt mineralisation during regional metamorphism: an example from the Rajapalot area, Finland

IF 4.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Mohammad Sayab, A. Menzies, R. M. Palin, A. R. Butcher, N. Cook, J. Kuva, Q. Dehaine
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Abstract

The Rajapalot area of Finnish Lapland hosts an unusually high-grade association of cobalt-only and gold–cobalt deposits (10.91 Mt @ 2.5 g/t Au + 0.44% Co total inferred resources) within multiply folded metasedimentary rocks of the Paleoproterozoic Svecofennian collisional orogeny. Through the integration of X-ray computed micro-tomography and micro-X-ray fluorescence raster imaging of drill-core samples, we produce a model of cobalt-bearing ore mineralisation, which reveals primary fluid transportation mechanisms and precipitation pathways. When combined with the deposit-scale, high-resolution ground-based magnetic geophysical data, we show that cobalt-bearing ores in the Rajapalot region occur mostly as saddle reefs located in dilated fold hinges, which formed by simultaneous synthetic and antithetic shearing along developing crenulation-cleavage planes and incompetent bedding layers, respectively. We suggest that multi-layered rock complexes with alternations of competent and incompetent layers deformed and metamorphosed to upper greenschist-lower amphibolite facies should represent focus regions for cobalt exploration targeting campaigns in orogenic belts. The non-destructive workflow presented in this study could be an integral part of an early stage of cobalt mineral processing and traceability before metallurgical treatment.

Abstract Image

区域变质作用对钴矿化的结构控制:芬兰拉贾帕洛特地区的一个实例
芬兰拉普兰的拉贾帕洛特(Rajapalot)地区在古新世斯维科芬尼碰撞造山运动的多褶皱元古代岩石中发现了高品位的纯钴矿床和金钴矿床(推断总资源量为1091万t @ 2.5 g/t Au + 0.44% Co)。通过对钻孔岩芯样本进行 X 射线计算显微层析成像和显微 X 射线荧光光栅成像的整合,我们建立了含钴矿化模型,揭示了主要的流体输送机制和沉淀途径。结合矿床规模的高分辨率地面磁性地球物理数据,我们发现拉贾帕洛特地区的含钴矿石主要以鞍状礁的形式出现在扩张的褶皱铰链中,这些鞍状礁分别是由沿发育的圆齿-劈裂面和无能的垫层同时发生的合成剪切和反剪切形成的。我们认为,在造山带的钴勘探活动中,具有上绿泥石-下闪长岩面变形和变质的有能层和无能层交替的多层岩石复合体应成为重点区域。本研究提出的非破坏性工作流程可作为冶金处理前钴矿物加工和追踪早期阶段的一个组成部分。
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来源期刊
Mineralium Deposita
Mineralium Deposita 地学-地球化学与地球物理
CiteScore
11.00
自引率
6.20%
发文量
61
审稿时长
6 months
期刊介绍: The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.
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