Arenites

Johnsson, M. J., Stallard, R. F., and Meade, R. H. (1988). First-cycle quartz arenites in the Orinoco River basin, Venezuela and Colombia. /. Geol. 96, 263-277. 

The Guadiana Basin occupies a total area of 66,850 km2 in Spain and Portugal, 8,350 km2 of which comprises the Iberian Pyrite Belt (IPB) one of the world s largest concentrations of base metal sulphide deposits (Leistel et al., 1997 Ribeiro et al., 1990). Three plant species (Cistus ladanifer, Lavandula luisieri and Thymus vulgaris) were utilized in this study. The soils in which these plants were sampled are developed over varied geological formations. The oldest formation (PQ Group, Upper Devonian) consists of a thick sequence of arenites and shales... 

Microlithofacial classification of the sandstones is based on Dott s classification modified by Pettijohn et al. (1972). They are mostly arenites and subarkose and quartz wackes (rare sublithic, sporadically lithic and arkosic). Quartz is the main component of the sandstones (about 60-70 vol. percent). Feldspars (6 vol. percent) are mostly represented by potassium feldspars with plagioclases in lesser amounts. Some micas (muscovite and biotite) and chlorites are observed. Mica content of arenites reaches 3 vol. %, but is higher in the wackes. Heavy minerals present include zircon, sphene, rutile and apatite. Magmatic rocks (volcanic more than Plutonic) are predominant among lithoclasts (about 2 vol. %), but some metamorphic and sedimentary clasts being present too. 

The detrital material is most frequently semi rounded and well sorted. It is rather loosely arranged in the arenites - the indicator of grain contacts in the sediment may be estimated at about 2.0. Point contacts are few, or absent in the wackes. 

The Carboniferous sandstones in the boreholes in LCB are represented by arenites and wackes, mainly quartz, subarkose and sublithic ... 

Improved magnetotelluric methods have detected deep conductors and shallow alteration zones in the search for deep unconformity-related deposits (Farqu-harson Craven 2008). Clay-rich, quartz-corroded quartz-arenite has relatively low resistivity, whereas quartz-rich silicified zones are characterized by high resistivity. Although expensive, 3D seismic has been used to image details of basement topology and more favourable areas for drilling. 

These unconformity-type deposits are located around the unconformity between the Helikian Athabasca Group sandstones and underlying Archean to early Proterozoic metamorphic basement (Hoeve Sibbald 1978 Hoeve Quirt 1984). The present sandstone cover ranges from 0 to 1500 m in thickness and is dominantly composed of mature coarse-grained quartz arenite with a kaolin-illite clay matrix. 

The Shin Formation of the Mabou Group is Early Carboniferous in age and shows a fining-upward sequence of pebble to boulder conglomerate. The Minto Formation of the Pictou Group is from the Late Carboniferous and contains cross-and horizontal-bedded feldspathic and quartzose arenite and pebble arenite. 

The McArthur River Uranium Deposit lies in the eastern portion of the Athabasca Basin and within the Churchill Structural Province of the Canadian Shield. The deposit straddles the unconformity between the quartz arenite - rich Late Paleoproterozoic Athabasca Group and... 

There are a few other terms commonly used to describe sandstones. A wacke is a poorly sorted sandstone containing more than 10% argillaceous material (clay). Arenites are well-sorted sandstones having little or no clay in them. An arkose is a sandstone whose particles are derived from plutonic rocks and so consist largely of quartz and feldspar. 

Iron formation, the sedimentary rock characterized by the association of chert and megaquartz with silicate, carbonate, and iron oxide minerals, is one of the most distinctive Precambrian sedimentary rocks. These rocks, which reached their peak in abundance during the Paleoproterozoic (Figure 2) (James, 1983 Isley, 1995), consist of both banded iron formations (BIFs) and granular (arenitic) iron formations (GIFs) and... 

Simonson B. M. (1987) Early silica cementation and subsequent diagenesis in arenites from four Early Proterozoic iron formations of North America. J. Sedim. Petrol. 57, 494-511. 

Simonson B. M. and Goode A. D. T. (1989) First discovery of ferruginous chert arenites in the Early Precambrian Hamersley Group of Western Australia. Geology 17, 269-272. 

De Ros L. F. (1998) Heterogeneous generation and evolution of diagenetic quartz arenites in the Silurian-Devonian Furnas Formation of the Parana Basin, southern Brazil. Sediment. Geol. 116, 99-128. 

Harris N. B. (1990) Diagenetic quartz arenite and destruction of secondary porosity an example from the Middle Jurassic... 

Makowitz A. and Sibley D. F. (2001) Crystal growth mechanisms of quartz overgrowths in a Cambrian quartz arenite. J. Sedim. Res. 71, 809-816. 

Donaldson, J. A. de Kemp, E. A. 1998. Archaean quartz arenites in the Canadian Shield examples from the Superior and Churchill provinces. Sedimentary Geology, 120, 153-176. 

Coarse grained arenites and conglomerates MOODIES GROUP... 

Matter, A. Ramseyer, K. (1985) Cathodoluminescence microscopy as a tool for provenance studies of sandstones. In Provenance of Arenites (Ed. ZufFa, G.G.), pp. 191-211. Riedel, Dordrecht. 

Diagenetic evolution of synorogenic hybrid and lithic arenites (Miocene), northern Apennines, Italy... 

This study aims to decipher and compare the dia-genetic evolution of hybrid arenites and arenites rich in carbonate rock fragments belonging to the Bismantova-Termina succession, a synorogenic sequence of the northern Apennines (Fig. 1). Special emphasis is given to the roles of the complex detrital composition, provenance and facies organization of the arenites in their carbonate cementation. 

Fig. 2. Schematic stratigraphy of the northern Apennines Epi-Ligurian sequences. (A) Upper Eocene-Lower Miocene succession. (B) Bismantova-Termina succession. S1-S4, depositional sequences B1-B3, arenite petrofacies. Bl, hybrid arenites B2, arkosic arenites B3, feldspathic lithic arenites 1, marls 2, resedimented arkosic and lithic arenites 3, hybrid arenites 4, silty marls. Modified from Amorosi Spadafora (1995).

The base of sequence 1 (SI) is bounded by an angular unconformity marked by a glaucony-rich horizon, and consists of hybrid arenites of marginal marine facies with shelf silty-marly deposits which locally interfinger with resedimented hybrid arenites (Fig. 3). An inversion of the sedimentation trend from coarsening upwards to fining upwards is associated with an increase in glaucony content, and has been chosen to define the boundary between SI and sequence 2. 

Sequence 2 (S2) consists of storm- and tide-influenced inner-shelf deposits passing to outer-shelf pervasively bioturbated, fine-grained arenites and siltstones. 

Sequence 3 (S3) starts with a 50 m thick lenticular body of resedimented arenites which overlies S2 with an erosional contact and passes upward to fossiliferous silty and clayey marls. S3 arenites are interpreted as channel-fill and shelf/slope deposits. 

The turbiditic arenites of S3 (Petrofacies B2) contain fewer carbonate intrabasinal grains (silici-clastic arkosic arenites) (Figs 4A,B and 5C). The siliciclastic fraction is qualitatively similar to that of sequences S1 and S2 (Fig. 4B,C) and came from the same source. 

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