Beckenanalyse 1: Economic Deposits in Sedimentary Environments …€¦ · extended to include...
Transcript of Beckenanalyse 1: Economic Deposits in Sedimentary Environments …€¦ · extended to include...
Beckenanalyse 1:Economic Deposits in Sedimentary Environments [M.Geo.136a]
Part 3: Ni-laterite, regolith, gossan
István DunklSedimentology, University of Göttingen
http://www.sediment.uni-goettingen.de/staff/dunkl/University of Göttingen
[1] Definitions, Mining economy in brief
[2, 3] Deposits related to weathering / residual sediments[2] laterite, bauxite, karst-bauxite [3] Ni-laterite, regolith, gossan
[4] Placer deposits (gold, zircon + rutile + ilmenite + REE, diamond, tin)
[5] Chemical sediments (Fe- and Mn-sediments, Kupferschiefer, phosphate )
[6] Exhalative, infiltration and metasomatic deposits (SEDEX, Kupferschiefer,
MVT-type deposits, Carlin-type gold deposits, sandstone-type U-ores)
[7 - 9] Combustable materials
[7] coal, [8] oil and gas, [9] some oil provinces & non conventional hydrocarbon (oil shale,
tar sand, shale gas, gas hydrate)
[10] Mineral processing
[Robb, 2005]
Ni-laterite
[Evans]
Ni-laterite
Synoptic profiles of major types of the Ni-laterite deposits of the Balkan Peninsula. Compiled according to: Ivanov, 1960; Augusthitis (1962); Arkaxhiu and Kici (1990); Skarpelis et al., 1996; Skarpelis, 1997; Eliopoulos and Economou-Eliopoulos, 2000; Peci and Grazhdani, 2001 and field observations of ID in 2004. (a)-(d): deposits of Cretaceous age. The first column (a) represents the most typical profile; the laterite deposited more-or-less autochtonously on the weathered ultrabsic rock. (b): The lateritic material was redeposited and covers slightly- or unwathered ultrabasite. (c) & (d): The lateritic material was resedimented on Mesozoic limestone. (e): the footwall and henging wall of the deposit is bordered by faults, the stratigraphic age of the cover sequenci is unknown. (f): Paleogene cover with alternating deposition of lateritic and siliciclastic material. (g): Deposits in the Miocene sequences.
Typical Ni-laterite profiles in the Balkan Peninsula
Geological setting of laterite ore deposits of the Edessa are, Greece a: Messimeri; b: Vrita; c: Flamuria (from Michaildis, 1990). These profiles show how different are the stratigraphicsuccessions even within a small area further these profiles are representing well the characteristic tilting and thrusting.
Ni-laterites in the Balkan Peninsula
[Edwards and Atkinson]
Ni-laterites
[Evans]
Ni-laterites
Regolith
[Craig, Wilford and Tapley, 1999]
Extract from a Regolith–Landforms Map.
Explanation of the regolith–landform codes, using channelsediments deposited on a river floodplain as an example.
[Robb, 2005]
Regolith
Definitions
[Robb, 2005]
[Robb, 2005]
Regolith
[Lintern, 1999]
Regolith
Regolithgeochemistry
(Southern
Australia)
[Lintern and Sheard, 1998]
Regolith mapping tools
[CSIRO, Australia]
A series of earth science tools have been employed to examine regolith profiles, in the field these include: surface sampling (vegetation, soils, lags, calcretes); profile sampling (Drilling – RC, Air Core, RAB, diamond core; pit excavation & natural exposures); materials mapping – distribution, provenance–genesis and depth of weathering. A variety of remote sensing tools have been applied to several field sites, these include: Landsat TEM, aeromagnetics, digital elevation-terrain modelling (DEM, DTM), air photography, infra-red spectroscopy (Landsat, HiMap, PIMA) and radar scanning imagery (TopSar, AirSar).
Landsat spectroscopy
[Das, 2002]
Usage of radar images in laterite mapping
[Tapley, 2004]
DEM generated from TOPSAR radar interferometry.
Variation in vertically polarized radar backscatter with changing surface roughness according to AIRSAR C, L and P band wavelengths, and a composite image of the three wavelengths. A previously unmapped NW-SE aligned linear feature [1] in the composite image is clearly evident
Glossary of commonly cited regolith terms I.
Arenose horizon: a sandy horizon, found above the pedoplasmation front, which consists of a grain-supported (or nearly so) fabric. The loss of lithic fabric appears to be caused by solution of weatherable primary and secondary minerals and settling of resistant minerals, dominantly quartz (cf. plasmic horizon),Colluvium: a general term for deposits on slopes or at the base of slopes that have been transported chiefly by mass flow. May be extended to include material that has been transported across surfaces by sheetwash, i.e. flowing water not confined to specific channels.Duricrust: indurated materials at or just below the surface. The material may be ferruginous, aluminous, siliceous or calcareous, or a combination of these. Siliceous and calcareous materials (cements) are normally referred to as silcrete and calcrete respectively. Significant induration by calcium sulphate is referred to as gypcrete.Hardpan: a subsurface indurated horizon. Red-brown hardpans in Australia are characterised by the presence of a porous matrix, commonly red-brown in colour, cemented by silica (usually hyalite), in a variety of transported or residual host materials.Horizon: a layer within the regolith approximately parallel to the land surface and differing from adjacent, genetically related, layers in physical, chemical and/or biological properties, or in characteristics such as colour, pH, structure, fabric, texture, consistency and types and numbers of organisms.
Lag: a veneer or pavement of fragments of diverse origins or composition on the land surface. Commonly applied to highly ferruginous concretions (in S. Aust. also applied to silcrete gibber). Fragments may be faceted, rounded and/or varnished.Mottled zone: an horizon, generally within the pedolith, characterised by localised spots, blotches and streaks of Fe oxides and oxyhydroxides that, with further mobilisation and concentration, become reorganised into secondary structures. Nodule growth gradually destroys pre-existing fabrics, although microfabrics may be preserved at the nucleus.Pallid zone: descriptive term, generally referring to bleached kaolinitic zones of the pedolith and saprolith occurring below the ferruginous and mottled zones, usually over felsic rocks. Use of the term is not recommended.Pedogenesis: soil formation.Pedolith: upper part of the regolith, above the pedoplasmic front, that has been subjected to soil forming processes resulting in the loss of the fabric of the parent material and the development of new fabrics, including secondary structures such as pisoliths. The podolith may develop from residuum, i.e. from saprolite, saprock or bedrock, or from transported overburden.Pedoplasmation front: transformation front at which the lithic fabric is destroyed, although commonly with little chemical reworking (pedoplasmation). It forms the boundary between the saprolite (or saprolith) and pedolith in deeply weathered profiles.
Glossary of commonly cited regolith terms II.
Plasmic horizon: the horizon in which the lithic fabric of the saprolite (or saprock) has been replaced by a new, mesoscopically homogeneous, plasmic fabric, above the pedoplasmationfront. The loss of lithic fabric is caused by solution and authigenesis of minerals and the mechanical processes such as shrink and swell of clays and settling of resistant primary and secondary minerals through instability induced by leaching. It consists of massive clays or siltyclays over rocks poor in quartz; a sandy arenose horizon forms over quartz-rich rocks. Major structural features, such as quartz veins and lithological contacts, may be preserved, probably with change in orientation (dip).Protolith: general term for parent material from which regolith has formed (i.e. bedrock).Regolith: see definition in Introduction.Saprock: compact, slightly weathered rock with low porosity, less than 20% of weatherableminerals altered. Weathering effects are present mainly at the microsites of contacts between minerals and intermineral fissures, along shears and fractures through the rock as a whole or affecting only a few individual grains or mineral species.Saprolite: weathered bedrock in which fine fabrics, originally expressed by the arrangement of the primary mineral constituents of the rock (e.g. crystals, grains) are retained. Compared to saprock, saprolitic material has more than 20% of weatherable minerals altered. Saprolite may be extended to include weathered rocks in which only larger structures such as bedding, schistosity, veining or lithological contacts are preserved. The presence of saprolite implies that weathering has been essentially isovolumetric.
Glossary of commonly cited regolith terms III.
Saprolith: the part of the regolith with a lithic fabric and potentially subdivisible into horizons, e.g. saprock and saprolite (cf. pedolith).Weathered bedrock: general term used to denote rock that has been chemically altered but which is still coherent, has some original structural elements preserved and is essentially in situwith no lateral physical movement having taken place (cf. saprolite, saprock).Weathering front: the transformation front marking the commencement of weathering at the base of the regolith. The rock-saprock interface.
[Adapted from: Govett, G.J.S., Butt, C.R.M. & Zeegers, H. (editors) 1992. Handbook of Exploration Geochemistry Volume 4. Regolith Exploration Geochemistry in Tropical and Subtropical Terrains. Elsevier, Amsterdam.]
[CSIRO, Australia]
Glossary of commonly cited regolith terms IV.
Gossan
[http://www.kamakazi.com/hake/gossan.html]
Gossan (capping, iron hat): an iron-bearing weathered product overlying a sulfide deposit. It is formed by the oxidation of sulfides and the leaching-out of the sulfur and most metals, leaving hydrated iron oxides and rarely sulfates.
Gossan
[Bauman et al.]
Major reactions in the oxidation and cementation zones
limonite
[Cissarz]chacocite
cuprite
Oxidation
Cemantation
covellite
Gossan
[Gocht, 1978]
Gossan
[Jensen and Bateman]
[Robb, 2005]
Gossan
Gossan
Cross section through the Chuquicamata mine showing the distribution of the supergene Blanket [after Ossadón et al., 2001 – in Robb, 2005]
Gossan
[Jensen and Bateman]