Texture and Trace Element Composition of Rutile in Orogenic Gold Deposits

Abstract

Rutile from a wide range of orogenic gold deposits and districts, including representative world-class deposits, was investigated for its texture and trace element composition using scanning electron microscopy, electron probe microanalysis, and laser ablation-inductively coupled plasma-mass spectrometry. Deposits are hosted in various country rocks including felsic to ultramafic igneous rocks and sedimentary rocks, which were metamorphosed from lower greenschist to middle amphibolite facies and with ages of mineralization that range from Archean to Phanerozoic. Rutile presents a wide range of size, texture, and chemical zoning. Rutile is the dominant TiO2 polymorph in orogenic gold mineralization. Elemental plots and partial least square-discriminant analysis suggest that the composition of the country rocks exerts a strong control on concentrations of V, Nb, Ta, and Cr in rutile, whereas the metamorphic facies of the country rocks controls concentrations of V, Zr, Sc, U, rare earth elements, Y, Ca, Th, and Ba in rutile. The trace element composition of rutile in orogenic gold deposits can be distinguished from rutile in other deposit types and geologic settings. Elemental ratios Nb/V, Nb/Sb, and Sn/V differentiate the rutile trace element composition of orogenic gold deposits compared with those from other geologic settings and environments. A binary plot of Nb/V vs. W enables distinction of rutile in metamorphic-hydrothermal and hydrothermal deposits from rutile in magmatic-hydrothermal deposits and magmatic environments. The binary plot Nb/Sb vs. Sn/V distinguishes rutile in orogenic gold deposits from other geologic settings and environments. Results are used to establish geochemical criteria to constrain the source of rutile for indicator mineral surveys and potentially guide mineral exploration.

A petrochronological study of Fe Ti oxides in rodingites of the Western Carpathians, Slovakia

“…The measured concentrations of V (1032 -3088 ppm), Sb (5 -570 ppm), and W (2 -825 ppm) together with very low Nb (< 97 ppm) and Cr (< 313 ppm) in both types of investigated rutile are in good agreement with their metamorphic-hydrothermal origin in an ultramafic-mafic system (Meinhold et al, 2008;Sciuba and Beaudoin, 2021). Likewise, low HFSE concentrations in both rutile types (Fig.…”

“…5) are comparable with those reported from rutiles occurring in mafic lithologies (Miller et al, 2007;Zack et al, 2002;Zhao et al, 2017). An extensive review of rutile composition from various geological settings shows that the trace element concentration depends not only on the chemistry of the host rock (ultramafic to felsic) but also on its metamorphic grade (Sciuba and Beaudoin, 2021). The difference in V concentration between rutile I and rutile II (2621 -2851 ppm and 1032 -2256 ppm, respectively) suggests that rutile I formed at higher metamorphic degree (upper greenschist facies) than rutile II (lower greenschist facies, Fig.…”

“…4), and 3) measured Si and Fe concentrations do not indicate significant contamination (Table S4). Although REE concentrations in rutile and ilmenite are not commonly reported in the literature, some investigations of rutile from felsic systems show that, in some cases, rutile can incorporate these elements (Meyer et al, 2011;Ngo Bidjeck Bondje et al, 2020;Schirra and Laurent, 2021;Sciuba and Beaudoin, 2021). The similar REE concentrations and REE patterns between investigated rutile II, ilmenite and titanite (Fig.…”

“…The systematic differences between the two types of rutile suggest that rutile I formed at higher temperature than rutile II. All diagrams are adopted from Sciuba and Beaudoin (2021).…”

Hydrothermal Alteration Processes of Xincheng Gold Deposit Jiaodong Peninsula, China: Constraints from Composition of Hydrothermal Rutile

“…Rutile is ubiquitously found in various types of rocks [14][15][16][17][18][19] and also forms in numerous hydrothermal deposits, such as orogenic gold deposits [20][21][22][23][24][25][26][27]. Due to its unique crystal structure, Ti ions often undergo isomorphic substitution with various trace elements of different valences [28][29][30][31], enriching rutile with trace elements and HFSEs such as W, Sn, Ta, Hf, Sb, Nb, and U [16,[32][33][34][35][36].…”