The use of fluorine as a pathfinder for volcanic-hosted massive sulfide ore deposits

Lavery, Norman G.

doi:10.1016/0375-6742(85)90015-9

Cited by 10 publications

(8 citation statements)

References 7 publications

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“…Alteration mineral assemblages and geochemical zoning patterns in the footwall rocks of many VHMS deposits have been extensively investigated because of their potential use as exploration guides (Ishikawa, 1976;Amor and Nichol, 1983;Moller et al, 1983;Reed, 1984;Lavery, 1985;Grunsky, 1986;MacLean, 1990). And the results of these investigations have been exploited by industry through empirical alteration indices and other lithogeochemical techniques in order to 0020-6814/93/26/1121-28 $10.00 improve the efficiency of VHMS exploration (Ishikawa, 1976;Spitz and Darling, 1978;Date et al, 1983;MacLean and Kranidiotis, 1987).…”

Section: Introductionmentioning

confidence: 99%

Lithogeochemical Exploration of Metasomatic Zones Associated with Volcanic-Hosted Massive Sulfide Deposits Using Pearce Element Ratio Analysis

Madeisky

Stanley

1993

International Geology Review

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Reactions between mineralizing hydrothermal fluids and host rocks produce distinct mineralogically and geochemically zoned alteration haloes in the footwall of many volcanic-hosted massive sulfide (VHMS) deposits, often very much larger than the deposits themselves. Empirical alteration indices have been developed to exploit these features and are widely used as geochemical vectors in the search for new deposits, but only with limited success. The principal limitation of using these indices as lithogeochemical exploration vectors is that they cannot distinguish between the geochemical modifications produced by hydrothermal alteration and the geochemical heterogeneity present in host rocks before the onset of hydrothermal activity. To overcome this problem, a theoretically based lithogeochemical exploration method has been developed that (1) identifies the sources of geochemical variability in VHMS host rocks, (2) isolates the pre-existing geochemical heterogeneity in these rocks through use of linear fractionation and crystal sorting models, and (3) quantifies material transfer due to hydrothermal metasomatism. This method has been applied to whole-rock geochemical data from footwall rhyolites, collected 250 m below the VHMS deposits at Rio Tinto, Spain. An alkali depletion anomaly is detectable 2.5 km from the deposits, increasing steadily in intensity from unaltered rocks at the margin to totally alkali-depleted rocks in the core of the footwall alteration halo. An Fe and Mg addition anomaly is detectable 1.5 km from the center of mineralization, also increasing toward the core of the alteration halo. The most intensively altered rocks in this set of samples also are the most evolved petrologically, suggesting the possible involvement of a latestage magmatic hydrothermal phase in the formation of the VHMS deposits at Rio Tinto. Given adequate sample density, this lithogeochemical method may be used to vector toward the core of a footwall (and probably also a hanging wall) alteration halo, and perhaps to massive sulfide mineralization.

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Section: Introductionmentioning

confidence: 99%

Lithogeochemical Exploration of Metasomatic Zones Associated with Volcanic-Hosted Massive Sulfide Deposits Using Pearce Element Ratio Analysis

Madeisky

Stanley

1993

International Geology Review

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“…Thallium might be a valuable pathfinder element in other ore systems as weIl. Lavery (1985) documented the value of fluorine as a pathfinder element in the search for volcanic-hosted massive sulphide deposits. Although fluorite is commonly considered not to occur in Sedex deposits (Maynard 1991), it does indeed occur.…”

Section: Data Interpretationmentioning

confidence: 99%

Lithogeochemical Investigations Applied to Exploration for Sediment-Hosted Lead-Zinc Deposits

Lavery¹,

Leach

Saunders

1994

Sediment-Hosted Zn-Pb Ores

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Sediment-hosted stratiform massive sulphide (Sedex) deposits and Mississippi Valley-type (MVT) deposits differ in morphology, but there is considerable overlap in their host rock lithology, regional setting, size, grade, metal ratios, age of host rocks, lead isotopes, sulphur isotopes, and genesis. Recent advances in the understanding of basin-derived formation fluids provide a framework for interpreting the lithogeochemical signatures of these deposits. The composition of the ore fluids for both types of deposits is controlled in part by fluid-rock reactions within sedimentary basins, but the nature of the sediments in the basins, the source of the fluids, the thermal gradient in the basin, the migratory history of the fluids, and the physical and chemical conditions in the deposition al environment cause variations in the lithogeochemical patterns present. Studies of modern sedimentary formation waters indicate that diagenetic fluid-rock reactions in basins can liberate and dissolve significant amounts of metals. The most metal-enriched formation waters are brines with more than 200000 ppm total dissolved solids. Some brines contain more than several hundred ppm combined Fe, Zn, Pb, and Ba, and minor amounts of Cu, Ag, Mn, Cd, As, Sb, Ni, Co, Mo, and Tl.Copper, Ag, As, Sb and Ba are reported in more than 60% of the Sedex deposits studied; Mn, Cd, Ni, Co, Au, Hg, Bi, B, Sn, Mo, F, Tl, Ge and Sr are reported in more than 20%; and V, Ga, In, Se, Cr and NH4 + are reported in more than 10% of the deposits. Geochemical variables which have received some exploration attention and which show promise as guides to Sedex deposits include: Tl, F, NH4 +, Hg, Pt, Pd, Zr, Cl-bearing minerals, rare earth elements, stable isotopes, and carbonaceous material.MVT districts were formed by ore-forming fluids which affected large volumes of the cmst. Widespread and isolated geochemical anomalies are, therefore, to be expected. Although there is a great diversity in deposit characteristics, it is possible to establish exploration criteria for additional deposits within a district or region. Geochemical analysis of insoluble residues has been used to define geochemical patterns that coincide with known ore trends and with ore-related geological features in the Southeast Missouri districts. Studies of rock alteration or identification of minerals precipitated from the brines can provide evidence of pathways used by the ore fluids. Hydrothermal dolomitization is the most important type of alteration; silicification is associated with ore in so me districts, and alteration of feldspars near ore has been identified in the Southeast Missouri lead district. Organic geochemistry and fluid inclusion studies are in progress and may yield practical exploration guides to MVT deposits.The presence of Cu, Mo, Pb, Zn, Ni, Co, Ag, Sb, As, Cd, and Ba in oil field brines/well scales, in MVT deposits, and in Sedex deposits lends credence to the use of these elements in lithogeochemical surveys. Many of the element associations described are bas...

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“…Available studies on the behaviour and distribution of F in natural rocks and fluids suggest that (i) F is strongly partitioned into the solid phases (iv) high F contents are common in rocks associated with massive sulphide deposits (Lavery 1985;Jiang et al 1994) and Au deposits (Matthtii et al 1995). Hence, it seems that pre-metamorphic F may persist in high-grade metamorphic rocks.…”

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confidence: 98%

“…The average F content in volcanic rocks is usually below 500 ppm; in F-enriched rocks it can easily rise to several thousand ppm. Anomalous F values often define a distinctive zone stratigraphically above and below the sulphide ores, and F contents are usually highest near ore bodies (Lavery 1985).…”

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confidence: 99%

“…Many volcanogenic massive sulphide (VMS) deposits occur in F-bearing hydrothermal systems, which are usually more voluminous than these ore deposits and therefore more easily recognizable (Lavery 1985). Hence, a geochemical exploration strategy is to use F as a pathfinder element to trace hydrothermal systems and then to locate possible ore deposits within the system.…”

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confidence: 99%

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Fluorine in orthoamphibole dominated Zn-Cu-Pb deposits: examples from Finland and Australia

Rajavuori

Kriegsman

2002

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Volcanogenic massive sulphide (VMS) deposits commonly occur within much larger fluorine (F)-bearing hydrothermal systems, where cordierite-orthoamphibole rocks are characteristic pathfinder assemblages. Here we report whole-rock and mineral F contents for orthoamphibole bearing rocks and associated rock types from Zn--Cu-Pb deposits in Finland (Orijtirvi, Iilij~irvi, Pyh~isalmi, Mullikkorgme) and central Australia (Oonagalabi). Textural and mineralogical data suggest that F influx predates peak metamorphism in these deposits.The Mullikkortime whole-rock data show positive correlations between F and XMg = molar Mg/(Mg + Fe) and between F and elements of relatively low mobility (Ti, A1, Mg) and negative correlations between Fe and these elements. This suggests that iron was leached from silicate rocks by F-bearing fluids and was transferred to the Fe-rich sulphide ore. When normalized to immobile elements, F correlates positively with total metal content (Cu + Pb ÷ Zn + Fe), consistent with the commonly observed increase of F content towards ore bodies.Combining all microprobe data, hydrous minerals show the following order of decreasing F/ (F + OH) ratio when coexisting: apatite > chondrodite > biotite > gedrite > (hornblende, muscovite, anthophyllite) > chlorite. The low-to medium-grade Finnish samples (Mullikkor-

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The use of fluorine as a pathfinder for volcanic-hosted massive sulfide ore deposits

Cited by 10 publications

References 7 publications

Lithogeochemical Exploration of Metasomatic Zones Associated with Volcanic-Hosted Massive Sulfide Deposits Using Pearce Element Ratio Analysis

Lithogeochemical Exploration of Metasomatic Zones Associated with Volcanic-Hosted Massive Sulfide Deposits Using Pearce Element Ratio Analysis

Lithogeochemical Investigations Applied to Exploration for Sediment-Hosted Lead-Zinc Deposits

Fluorine in orthoamphibole dominated Zn-Cu-Pb deposits: examples from Finland and Australia

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