Assessment of crystallographic orientation effects on secondary ion mass spectrometry (SIMS) analysis of cassiterite

Abstract

Crystallographic orientation effects on ion microprobe analyses for U-Pb and Oisotopes have been reported for a number of oxide minerals, including rutile (TiO2) and baddeleyite (ZrO2). Here we evaluate the effects of crystal orientation on U-Pb and Oisotopic data measured by ion microprobe on cassiterite (SnO2), which is isostructural with rutile. The crystallographic orientations of mounted and polished grains of cassiterite were determined by electron backscatter diffraction (EBSD). Those grains were then analysed for U-Th-Pb isotopes and 18 O/ 16 O compositions using the SHRIMP RG and SHRIMP SI ion microprobes, respectively. Based on these data, cassiterite appears to show no dependence of key measurement parameters such as UO2/UO, Pb/UO, or 18 O/ 16 O ratios at the achieved precision with crystallographic orientation. The contrasting behaviour of isostructural cassiterite and rutile provides new insights into the mechanisms leading to crystallographic orientation effects during ion microprobe analyses with electronic structure proposed as being a significant factor.

Advances and Opportunities in Ore Mineralogy

“…EBSD has also proven most helpful in examining potential variation in isotopic signature with crystal orientation of iron-oxides [72], rutile [73], or cassiterite [74]. Because electron backscatter patterns are generated from the uppermost few tens of nanometres of the sample surface, preparation and chemical polishing routines need to be optimised.…”

U/Pb geochronology of wolframite by LA-ICP-MS; mineralogical constraints, analytical procedures, data interpretation, and comparison with ID-TIMS

“…2005). Additionally, there is a major isobaric interference between 204 Pb and 186 W 18 O during ablation of wolframite requiring a mass resolution of ~12,000 (e.g.,Carr et al 2017), which is significantly higher than the 300 used in this study. Achieving such a high mass resolution will inherently reduce signal intensity and is not feasible for U/Pb dating application of wolframite by LA-ICP-MS.…”

LA–ICP–MS U–Pb Dating, Elemental Mapping and In Situ Trace Element Analyses of Cassiterites from the Gejiu Tin Polymetallic Deposit, SW China: Constraints on the Timing of Mineralization and Precipitation Environment

“…Cassiterite (SnO 2 ) is the most important ore mineral for tin deposits and has a tetragonal lattice structure similar to that of the rutile group (M 4+ O 2 ) [1][2][3][4]. Because cassiterite is resistant to chemical and physical alteration and weathering, trace elements, such as Fe, Ti, W, Zr, Hf, Ta, Nb, Mn, Sc, V, and Sb in cassiterite could be used to study mineralization processes and precipitation environments of tin mineralization [2][3][4][5][6][7][8][9][10]. Furthermore, the presence of U and Pb makes it possible to date cassiterite with U-Pb geochronology [1,2,4,[7][8][9][11][12][13][14][15].…”

“…Because cassiterite is resistant to chemical and physical alteration and weathering, trace elements, such as Fe, Ti, W, Zr, Hf, Ta, Nb, Mn, Sc, V, and Sb in cassiterite could be used to study mineralization processes and precipitation environments of tin mineralization [2][3][4][5][6][7][8][9][10]. Furthermore, the presence of U and Pb makes it possible to date cassiterite with U-Pb geochronology [1,2,4,[7][8][9][11][12][13][14][15]. Thus, cassiterite can be used to investigate mineralization timing, precipitation environment, and mechanisms for magmatic-hydrothermal ore deposits or important tin belts worldwide [3,4,16,17].…”