Laser ablation ICP-MS study of trace elements in scheelite in different types of mineralization from the Bohemian Massif

Abstract

We describe scheelite in five types of mineral deposit from the Bohemian Massif (greisen, orogenic Au, reduced intrusion-related gold systems (RIRGS), oxidized and reduced skarn) via cathodoluminescence (CL) imaging and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses. We document variability in the scheelite composition within single grains and/or deposit types that reflects the nature and evolution of the ore-forming fluids. We provide scheelite typical trace element characteristics and chondrite-normalized REE patterns for different deposit types, confirming that scheelite can be used as an indicator mineral for their exploration. For example, scheelite from greisen-related deposits is usually rich in Sn, Sr, Y and HREE with various ranges of median values in individual deposits (0.05–8.0 ppm, 232.4–567.1 ppm, 0.06–465.0 ppm and 0.06–632.5 ppm, respectively) and with typical chondrite-normalized REE patterns showing Eu negative or positive anomaly. Under UV light scheelite from Sn-W deposits displays variable colours from whitish via yellowish to bluish. In contrast to greisen-related deposits, scheelite from Au-orogenic association is usually relative rich in Pb (median range in individual deposits: 6.1–11.2 ppm), and relatively poor in Mg, Mo and Nb. Flat and bell-type chondrite-normalized REE patterns show a pronounced Eu positive anomaly. Under UV light it is predominantly homogenous and bluish. Scheelite from oxidized skarn is enriched in Mo, Nb and ΣLREE (median range in individual deposits: 311.4–7214.1 ppm, 1.3–214.9 ppm, and 1.1–1375.8 ppm, respectively), and scheelite from reduced skarns is characterized by the lowest median ranges of Nb (1.7–107.8 ppm), Y (0.69–41.1 ppm), Mn (0.5–17.0 ppm) and Zn (0.04–0.252 ppm) in individual deposits, when compared to all the groups studied. Scheelite from oxidized and reduced skarn deposits displays several types of chondrite-normalized pattern: (1) LREE-enriched with a positive or negative Eu anomaly, (2) Bell-shaped REE patterns with negative or without Eu anomaly, and (3) Flat REE patterns with a negative Eu anomaly. Scheelite from oxidized and reduced skarn deposits is commonly zoned and mostly bluish under UV light.