John Allen: Technical Services

Thin sections (27x46mm) for petrography of non-opaque minerals

Polished thin sections (27x46mm) for non-opaque and ore mineral petrography, and microprobe analysis

Polished mounts (2.5cm diameter) of ore minerals drill cuttings

Polished thin section grain mounts (2.5cm diameter) of alluvial concentrates, mill concentrates, drill cuttings

Fluid inclusion plates (double sided polish)

Non-opaque mineral petrography of thin sections (transmitted light microscopy). Mineralogy and textures of fresh and altered silicate rocks, carbonate rocks, oxide ores.	Opaque and non-opaque mineral petrography of polished thin sections (combined reflected and transmitted light microscopy). Mineralogy and textures of ore and gangue minerals.
Oxide copper ore (malachite-azurite), Ok Tedi, PNG. (thin section)	Molybdenite-chalcopyrite mineralisation in porphyry, Maria mine, Sonora, Mexico. (polished thin section)

Cathodoluminescence (CL)

Mineral growth textures
Correlation of luminescence with mineral composition
Typing and source of alluvial grains

Ultraviolet luminescence (UVL)

Identification of luminescent phases, e.g scheelite

CL image of rare-earth mineralised carbonatite from
Mali, West Africa. Phenocrysts of Fe-Mg-Mn calcite
(red) and apatite (blue) in a calcite matrix (orange).

Heavy indicator minerals

Mineral concentration and separation
Hand picking
Mineral compositions by electron microprobe analysis
Bedrock source characterisation

Mature alluvial gold sourced from the
Derewo Metamorphic Belt, West Papua

K-feldspar, in cut slabs, offcuts or thin sections: e.g. to show adularia alteration around mineralised quartz veins

Dolomite, in cut slabs, offcuts or uncovered thin sections: e.g. to distinguish from calite in hydrothermal carbonate-altered rocks, and in quartz-carbonate-sulfide veins

K-feldspar alteration haloes (stained yellow)
around quartz-molybdenite veins.
Magistral Cu-Mo porphyry, Peru.

Photos of rocks, slabs and offcuts, to, show overall relationships of sample features, eg. veins, alteration

Photomicrographs of thin and polished thin sections, e.g. to show ore minerals,veining, alteration, textural relationships, overprinting

Quartz and chalcopyrite stockwork veining,
Grasberg Cu-Au porphyry, West Papua.
(polished slab)

XRD identification of unknown minerals, including clays which may require heating and /or glycolation for conclusive identification

Acid alteration to alunite-kaolinite-leucoxene,
Lihir epithermal gold deposit, PNG.
(thin section)

Electron microbeam analysis of minerals in polished thin section, for example:

Identification of unknown minerals of potential economic interest
purity (fineness) of gold
gold composition (Au, Ag, Cu, Hg, Pd) as an indicator of provenance and style of mineralisation in bedrock source
determination of hosts for low abundance and trace elements of economic interest, e.g. of Pd in gold
Backscattered electron imagery and photography to map element concentrations, and observe textural relationships of minerals

Alluvial grain of auroan copper with
exsolved auricupride (AuCu), sourced
from the West Papua ophiolite
(BSE image of polished section)

Microscopic textures of mineral grains, e.g. of detrital features in alluvial gold	Qualitative mineral analysis: Energy-dispersive scan of mineral composition. Mineral identification
Overflattened, polycrystalline alluvial gold grain, sourced from the Grasberg Cu-Au porphyry, West Papua	EDS scan of uraninite, Dawn Lake, Saskatchewan, Canada.

Heating measurements of fluid inclusion homogenisation temperatures, to infer paleotemperatures in hydrothermal systems

Freezing meaasurements to infer compositions of hydrothermal fluids and their origin

Oxygen, hydrogen, carbon and sulfur isotope analyses to infer fluid history and fluid sources, e.g. juvenile, meteoric, mixed fluids

Geothermometry, e.g. from sulfur isotope fractionation between coexisting sulfides

Postal address:
PO Box 32-290, Devonport
Auckland, New Zealand

Courier address:
42 Aramoana Ave, Devonport
Auckland, New Zealand

Phone, Fax:
Tel +64 9 445 8822
Fax +64 9 445 8848