Babingtonite and Fe-rich Ca-A1 silicates from western Southland, New Zealand

Duggan, M. B.

doi:10.1180/minmag.1986.050.358.11

Cited by 6 publications

(5 citation statements)

References 11 publications

(16 reference statements)

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“…In epidote and axinite, Fe is considerably higher in the rims; in epidote Fe203 reaches 25.8% (PS54.5). Similar Fe-rich epidote associated with babingtonite has been reported by Duggan (1986). In gamet, Fe decreases and Mn and Al increase in outer zones where birefringent zones are associated with higher contents of the grossular molecule.…”

Section: Skarn Typessupporting

confidence: 80%

“…At Three Kings Islands, babingtonite is found with Fe-rich prehnite and epidote in spilite (Battey, 1954). It has also been recorded from the Takitimu Group of western Southland, in calcareous tuff in pillow lava interstices (Duggan, 1986). Both occurrences are in low grade regionally metamorphosed rocks, and in both the babingtonite is scarce, present as small crystals, and contains only minor amounts of MnO.…”

Section: Skarn Typesmentioning

confidence: 90%

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Tertiary limestone and Zn-Pb mineralised skarn at Motukokako, Cape Brett, northern New Zealand

Brathwaite¹,

Isaac²,

Challis³

et al. 1990

Journal of the Royal Society of New Zealand

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Motukokako, 1 kIn northeast of Cape Brett, Northland, New Zealand, is composed of Waipapa "basement" greywacke and argillite of Permian-Jurassic age, unconformably overlain by moderately dipping (?)Oligocene Whangarei Limestone. The nearest Whangarei Limestone onshore is 37 km to the southwest, at Kawakawa. Both the Waipapa rocks and Whangarei Limestone are cut by a series of subvertical Zn-Pb-Cu mineralised quartz veins. At the northern end of Motukokako, the Whangarei Limestone is altered to Zn-Pb mineralised calc-silicate skarns, formed by metasomatic reaction between the limestone and the hydrothermal fluids which penetrated along fractures that were later filled by the quartz veins. Prograde hedenbergite-garnet-epidote-axinite skarn is the dominant type; it is cut and replaced by retrograde ilvaite-babingtonite skarn, mainly along subvertical zones adjacent to the quartz veins. Sphalerite and galena are disseminated in the hedenbergite-garnet-epidote skarn, and also in the adjacent silicified recrystallised limestone. The mineralisation is generally low grade (1-6% Zn and 0.2-1 %Pb). Some of the zinc is contained in axinite and in sauconite, a Zn-rich smectite. Hedenbergite, axinite, ilvaite and babingtonite are notably enriched in Mn, while epidote and garnet (andradite) are Fe-rich varieties. No igneous rocks are known in the vicinity; the most likely source for the hydrothermal fluids that produced the skarn is an Early Miocene quartz diorite-granodiorite stock at depth, similar to those now exposed at Cape Karikari and Coppermine Island.

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Section: Skarn Typessupporting

confidence: 80%

Section: Skarn Typesmentioning

confidence: 90%

Tertiary limestone and Zn-Pb mineralised skarn at Motukokako, Cape Brett, northern New Zealand

Brathwaite¹,

Isaac²,

Challis³

et al. 1990

Journal of the Royal Society of New Zealand

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“…Since cuprospinel is only found in ore dumps on mining property and forms as a byproduct of mineral extraction processes (Anthony et al 1997), it seems likely that the chalcopyrite is being converted to delafossite. Delafossite can be primary in origin or secondary as a product of chalcopyrite oxidation (Duggan 1986;Ramadan and Kontny 2004). The investigations of McKinstry (1959) indicate that the associations and natural conditions of stability of delafossite were not well understood and little investigation into the natural occurrences of the mineral appears to have been carried out since.…”

Section: Discussionmentioning

confidence: 99%

A study of the trace sulfide mineral assemblages in the Stillwater Complex, Montana, USA

et al. 2016

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The sulfide assemblages of the Stillwater Complex away from the well-studied ore zones are composed mainly of variable proportions of pyrrhotite, chalcopyrite, pentlandite, and ±pyrite. Excluding vein assemblages and those affected by greenschist and lower temperature alteration, the majority can be classified into two broad assemblages, defined here as pristine (multiphase, often globular in shape) or volatilebearing (multiphase, high-temperature, volatile-rich minerals such as biotite, hornblende, or an unmixed calcite-dolomite assemblage). The volatile-bearing assemblages are mainly found within and below the J-M reef, where native copper and sphalerite are also locally present. Pristine sulfides are found throughout the stratigraphy. Both groups can be affected by apparent S loss in the form of pyrite being converted to magnetite and chalcopyrite to a Cu-Fe-oxide (delafossite), with little to no silicate alteration. An upward trend from pentlandite-rich to pyrrhotite-rich to pyrite-rich assemblages is observed in the footwall rocks in upper GN-I, and the same trend repeats from just below the reef and continues into the overlying N-II and GN-II. Modeling suggests that the sulfide Ni in the Peridotite Zone is largely controlled by silicate Ni. When taken together, observations are most readily explained by the remobilization of selected elements by a hightemperature fluid with the apparent loss of S > Cu > Ni. This could concentrate ore metals by vapor refining, eventually producing a platinum group element-enriched sulfide ore zone, such as the J-M reef.

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“…Tulloch concluded that the alteration process responsible for the development of the garnets and associated minerals was deuteric, and that, in contrast to the prehnite-pumpellyite facies of the nearby Wakatipu metamorphic belt which developed in a high-to intermediate-pressure facies, the prehnitepumpellyite (and associated grandite) facies alteration in the Tasman Belt granitoids was developed at considerably shallower depths under relatively low-pressure conditions. Duggan (1986), in a contribution on Fe-rich Ca-Al silicates developed in volcanic detritus occurring in the interstices of basaltic pillow lavas of the Permian Takitumu Group, western Southland, New Zealand, noted the development of babingtonite, Fe-rich prehnite, grandite garnet, quartz, calcite, chlorite and pumpellyite. On the basis of textural and chemical evidence Duggan concluded that 'the babingtonite, Fe-rich epidote, calcite and quartz formed from hydrothermal solutions by direct precipitation in open cavities and by replacement of higher-temperature silicate phases (in particular plagioclase and basaltic glass) in a shallow marine volcanic environment.…”

Section: (Vii)mentioning

confidence: 99%

The precursor principle and the possible significance of stratiform ores and related chemical sediments in the elucidation of processes of regional metamorphic mineral formation

Stanton

1989

Phil. Trans. R. Soc. Lond. A

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This contribution is concerned with the regional metamorphism of fine-grained (pelitic) sedimentary materials, and with the pelitic components of coarser sediments. It emphasizes the possible importance of purely chemical sedimentary rocks, and the preservation of chemical patterns within them, in the elucidation of some regional metamorphic mineralogical processes. The materials and examples used come largely from the category of exhalative sediments, of which stratiform metallic sulphide orebodies and their associated exhalites are important members. A few examples come from volcanic rocks that have been altered by exhalative processes. The special significance of chemical sediments stems from their propensity for the development of highly complex metamorphic silicate mineral assemblages within relatively minuscule volumes of rock, and from their commonly sharply defined chemical bedding and chemical sedimentary facies patterns. As the primary nature of such chemical bedding and chemical layering and zoning in completely unmetamorphosed materials is observable and known, and as their sharp boundaries and other well-defined features can be examined in a full range of unmetamorphosed to highly metamorphosed environments, they may be used as extremely sensitive markers for the detection and measurement of any chemical movement that may have taken place during regional metamorphism. Detailed examination of such evidence appears to indicate a general lack of diffusion and reaction, and a common lack of attainment of mineral equilibrium, in the development of the regional metamorphic silicate assemblages of a number of such stratiform ore deposits and their associated exhalative materials. This, together with the common interbedded nature of metamorphic silicate, sulphide, carbonate, etc., and the faithful maintenance of primary sedimentary chemical facies patterns within many exhalative metasediments suggests that the silicates, like the accompanying sulphides and associated compounds, may derive directly and in situ from early-formed precursor materials rather than from extensive elemental diffusion and metamorphic reaction. That particular clays and zeolites derive from specific precursors in many instances has been recognized for a long time. That many metamorphosed bedded oxides (including quartz), together with carbonates, sulphates, sulphides and authigenic silicates such as the feldspars, have derived from sedimentary: diagenetic precursors is self-evident and unavoidable, and establishes precursor derivation for at least some regional metamorphic minerals as a principle, not an hypothesis. What is not known, however, is the extent to which this principle applies to the broader spectrum of metamorphic silicates. The present contribution examines this problem. The evidence of ‘ metamorphic ’ silicates in a range of unmetamorphosed and littlemetamorphosed rocks, in present ocean-floor sediments, in unmetamorphosed volcanic alteration products and in modern geothermal systems is examined. The preservation of possible precursor materials in a variety of rocks, and the synthesis of a number of ‘ metamorphic ’ minerals by low-temperature solution experimentation and in low-temperature industrial products is considered. It is deduced that most of the well-known regional metamorphic minerals may in fact be produced directly from low-temperature sedimentary/diagenetic/alteration materials, and that such precursors may be of simple or complex kind. It is suggested that the direct derivation of regional metamorphic silicates from precursors may resolve the problem of the elusive metamorphic mineral reaction, and that the principal regional metamorphic grade indicators may be the temperatures of precursor transformations rather than temperatures of reactions. Several implications of the precursor principle are then examined: its significance in the interpretation of zoning of regional metamorphic mineral assemblages and mineral chemistry; in considerations of metamorphic grade and the development of grainsize; in the identities of certain metamorphic equilibria, intergrowths and ‘retrograde’ materials; and in the deduction of earlier environments of rock formation and alteration. In this general connection it is proposed that the overall regional metamorphic process may be substantially indigenous: that through their primary nature certain materials, e.g. some andesitic-dacitic volcaniclastic rocks, may be predisposed to metamorphose themselves, and that this may be accentuated by the petro-tectonic setting in which they form, e.g. island arc - eugeosynclinal provinces, with their characteristically inter-related calc-alkaline volcanism, riftrelated palaeogeographical features and highly patterned heat flow. Effects of climate may be superimposed on this: some of the more highly developed regional metamorphic zoning may arise in calc-alkaline volcanic sediments deposited in tropical island arc shelf areas, and in sediments laid down in large saline lakes of continental volcanic rift provinces. From all this it is proposed that the ambit of regional metamorphic petrology may be much wider than currently visualized. Just as precursor-derived oxides, carbonates, sulphates, graphite, pyrite, etc., of high-grade metasedimentary rocks may give clear indications concerning the nature and environments of formation of the original sediments, so the metamorphic silicates may yield subtle insights into palaeoprovenance, palaeogeography, palaeoclimate and a variety of weathering, volcanic alteration, sea-floor hydrothermal and other regimes. The application of metamorphic mineralogy and mineral chemistry to the search for stratiform ores in metamorphosed terranes may constitute one of the major advances in mineral exploration in the near future. It appears that there is considerable scope for further searching for possible precursor material in a variety of rocks and modern sediments (especially those of the present-day volcanic-sedimentary milieu), extension of clay and mixed-layer clay-chlorite-zeolite mineral synthesis in low-temperature-pressure laboratory experiment, and for the investigation of the behaviour of these synthetic products at metamorphic temperatures and pressures.

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Babingtonite and Fe-rich Ca-A1 silicates from western Southland, New Zealand

Cited by 6 publications

References 11 publications

Tertiary limestone and Zn-Pb mineralised skarn at Motukokako, Cape Brett, northern New Zealand

Tertiary limestone and Zn-Pb mineralised skarn at Motukokako, Cape Brett, northern New Zealand

A study of the trace sulfide mineral assemblages in the Stillwater Complex, Montana, USA

The precursor principle and the possible significance of stratiform ores and related chemical sediments in the elucidation of processes of regional metamorphic mineral formation

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