Use of tourmaline in stream sediments to detect submarine exhalative sulfide deposits: example from central Virginia, U.S.A.

Robinson, G.D.; Healey, Karen; Kelly, Valerie Carney

doi:10.1016/0883-2927(88)90010-8

Cited by 8 publications

(2 citation statements)

References 6 publications

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“…However, caution must be exercised when using tourmaline compositions because Fe-rich tourmalines may be associated with some deposits (e.g., Broken Hill, Kidd Creek). Although exploration programs may focus on the distribution of tourmalinites in the field, several stream sediment studies have demonstrated the potential of Mg-rich tourmaline as an exploration guide to massive sulfides, due to its chemical and mechanical stability and its relatively high specific gravity (Pavlides et al, 1982;Slack, 1982;Robinson et al, 1988;Robinson, 1989).…”

Section: Exploration Applicationsmentioning

confidence: 99%

Metamorphic and Metamorphogenic Ore Deposits

Vokes¹,

Marshall²,

Spry³

1998

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Meta-exhalites consist of a variety of rock types including iron formation, coticule (garnet-quartz rock), tourmalinite, quartz-gahnite rock, apatite-rich rock, zincian staurolite-bearing rock, and barite-rich rock. Such lithologies may be spatially associated with a diversity of ore deposits, but they are particularly linked to sea floor base metal sulfides that formed in rift settings. Meta-exhalites generally form layers less than 2 m thick, above, below, in, and along strike from stratiform or exhalative ore deposits. Geochemical diagrams for iron formations, coticules, and tourmalinites (chondrite-normalized rare earth element (REE), ternary Al-Fe-Mn, Al/ (Al+ Fe+ Mn) vs. Fe/Ti, Ti0 2 vs. Al 2 0 3 ) suggest ~riable contributions of detrital material and hydrothermal components, The detrital component, terrigeilous or elastic, is generally less than 30 wt percent for iron formations, whereas for coticules and tourmalinites it is generally 30 to 70 wt percent and greater than 70 wt percent, respectively. Of the major constituents of meta-exhalites, Fe, Mn, B, P, and Zn generally have a hydrothermal source, whereas Al and Ti are from detrital elastic material. Silica can have hydrothermal and/ or detrital sources. Hydrogenous contributions are generally small.The variable setting, mineralogy, primary sedimentary structures, geochemistry, and lithological variants of exhalites show that precursor constituents formed under a variety of physicochemical conditions (e.g., T, fo 2 , pH, ionic strength, Js 2 , fco 2 ) and were derived from different sources (elastic and volcanic).Iron formations, coticules, and tourmalinites form by the replaceme9t of permeable aluminous sediment~ and by exhalation into submarine brine pools. Hydrothermal fluids responsible for the formation of precursors to meta-exhalites range in temperature from approximately 100° to 400°C. Layering in meta-exhalites reflects rapid fluctuations in Eh-pH conditions, metal contents, f 82 , Jc 02 , and detrital input. Fractionation of Fe and Mn in the hydrothermal fluids is due to gradual increases in pH_ or Eh during mixing of ambient seawater with the fluids and may account for differences in proximity br"iron formations and coticules to sulfide deposits. The amount of hydrothermal input via venting, fluid/ rock ratio, bottom current drift, and the degree of basin isolation from elastic sedimentation also dictate the chemical composition and mineralogy of meta-exhalites.The presence of a meta-exhalite is indicative qf a fossil zone of sea floor hydrothermal activity and, as such, can be utilized as a field guide in the exploration for ore deposits, particularly base metal sulfides. Relative abundance of certain minerals (e.g., iron carbonates, apatite, gahnite, zincian staurolite), bulk compositional variations that record increased ratios of hydrothermal components to detrital material, characteristic elements and elemental ratios, variations in the compositions of mineral phases (e.g., Zn to Fe ratio of staurolite, gahnite, and hogbomite as well a...

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Section: Exploration Applicationsmentioning

confidence: 99%

Metamorphic and Metamorphogenic Ore Deposits

Vokes¹,

Marshall²,

Spry³

1998

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“…Chemical variation in tourmaline has been used as a recorder of magmatic evolution in that increasing degrees of magmatic differentiation typically are accompanied by decreasing schorl and dravite components with a corresponding increase of elbaite component, reflecting the dominant Li+Al for Fe+Mg substitution at the Y site (e.g., Staatz et al 1955;Power 1968;Neiva 1974;Foord 1976;Lister 1979;Manning 1982;Jolliff et al 1986Jolliff et al , 1987Taylor et al 1992). Tourmaline occuring in different metallic ore deposits, such as massive sulfide, gold lode, and tin-tungsten, has been shown to be useful in exploration of each of these types of deposits (e.g., Slack 1982Slack , 1996Pirajno and Schlogl 1987;Robinson et al 1988;Robinson 1989).…”

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confidence: 97%

Cr-bearing tourmaline associated with emerald deposits from Swat, NW Pakistan: Genesis and its exploration significance

Arif

Henry

Moon

2010

American Mineralogist

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Carbonate-talc altered ultramafic (and mafic) rocks of the obducted oceanic lithosphere along the Main Mantle Thrust in the Swat Valley host emerald deposits and are invaded by quartz veins and stockworks. Both the quartz veins and carbonate-talc altered rocks contain discrete grains and clusters of tourmaline crystals, which may be associated with emerald and/or chromian muscovite. Tourmalines from the Mingora and Gujar Kili emerald mines and the Spin Obo-Kuh area are Nibearing, Cr-rich dravites and "oxy-dravites" that exhibit substantial chemical variability with 2.0-2.5 atoms per formula unit (apfu) Mg, relatively low Al (4.8-5.8 apfu), high Cr (0.5-1.8 apfu), high Cr/(Cr+Al) ratios of 0.08-0.28, significant amounts of Ni (up to 0.11 apfu), and variable calculated W site O 2-(0.2-0.8 apfu). The mechanisms that appear to control the tourmaline chemistry at these localites are combinations of the dominant substitution Al = Cr with lesser amounts of the Mg+OH 1-= (Al,Cr)+O 2-and Al 3+ = Fe 3+ substitutions. Relative to the Mingora, Gujar Kili, and Spin Obo-Kuh areas, the Charbagh tourmalines are "oxy-dravites" that have comparable Mg contents (2.2-2.3 apfu) with variable calculated W site O 2-(0.6-0.9 apfu), but are more Fe-rich (0.5 apfu) and Al-rich (6.0-6.3 apfu) with low Cr (0.00-0.01 apfu) and Ni contents (0.01-0.02 apfu). The mechanism that appears to control the variable chemistry of the Charbagh tourmalines is primarily Mg+OH 1-= Al+O 2-. The chemical characteristics of tourmalines from the various localities relate most clearly to differences in host rock chemistry.Tourmalines from the carbonate-talc altered ultramafic-mafic rocks and the invasive quartz veins have a common hydrothermal origin associated with emplacement and crystallization of younger granitoids. Furthermore, the occurrence of Swat emeralds in quartz-tourmaline (±chromian muscovite) veins suggests that the tourmaline is cogenetic with emerald formation. The quality and quantity of Swat emeralds depend on the: (1) host rock composition and (2) nature of the hydrothermal fluids. Large deposits of gem-quality emerald occur in carbonate-altered ultramafic rocks, which also contain Cr-rich dravites and "oxy-dravites." This suggests that the presence of high-Cr magnesian tourmalines, particularly in magnesite-talc altered ultramafic rocks, can represent a criterion for further emerald exploration in the lower Swat region of Pakistan and comparable ultramafic-hosted emerald-producing regions.

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Mineralogy, geochemistry and geological significance of tourmaline-rich rocks from the Paleozoic Cinco Villas massif (western Pyrenees, Spain)

Pesquera

Velasco

1997

Contributions to Mineralogy and Petrology

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Use of tourmaline in stream sediments to detect submarine exhalative sulfide deposits: example from central Virginia, U.S.A.

Cited by 8 publications

References 6 publications

Metamorphic and Metamorphogenic Ore Deposits

Metamorphic and Metamorphogenic Ore Deposits

Cr-bearing tourmaline associated with emerald deposits from Swat, NW Pakistan: Genesis and its exploration significance

Mineralogy, geochemistry and geological significance of tourmaline-rich rocks from the Paleozoic Cinco Villas massif (western Pyrenees, Spain)

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