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Jacobina - Morro do Vento, Itapicuru, Joao Belo, Canavieiras |
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Bahia, Brazil |
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Au U
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Jacobina conglomerate hosted Au, U deposit is located some 330 km north-west of Salvador, in Bahia State, central Brazil.
The mountains of the Serra de Jacobina have been mined for gold since the late 17th century, with numerous artisanal (garimpeiro) workings/garimpos distributed over a 15 km strike length along the ridges of the Serra do Ouro mountain chain. Companhia Minas do Jacobina operated the Gomes Costa Mine in the Morro do Vento area between 1889 and 1896, with total production of 84 kg of gold from a 130 m long drive. The Canavieiras, João Belo, and Serra Branca mines opened in the 1950s, the largest of which was the first of these operations, with a capacity of 30 tpd. It produced 115 653 t with an average recovered grade of 18.13 g/t Au during the 1950s and 1960s. Modern exploration began in the early 1970s when Anglo American Corporation investigated the area. As a result of that work the first mine was commissioned in October 1980 at Itapicurú (Morro do Vento) with the first full year of operation in 1983, producing 241 703 t @ 5.73 g/t Au for 1.1 tonnes of gold. Continued exploration from 1984 to 1987 resulted in an open pit being established at João Belo Norte Hill in August 1989, followed by an underground mine at João Belo. The mines closed in December 1998 due to a depressed gold price. Between 1983 and 1989, 7.96 Mt @ 2.62 g/t Au(recovered),yielded ~20.8 tonnes of gold. The João Belo Mine was reactivated in 2004, and the Morro do Vento mine in 2005. With continued mining since then, the cumulative production from 1983 has totalled >33 Mt of tonnes of ore @ 2.19 g/t gold for a production of >68 tonnes of gold.
The deposit occurs within the north-south oriented, preserved section of the Jacobina basin, which has historically been variously interpreted to have been deposited at ~3.4 to 3.2 Ga or between 2.4 and 2.07 Ga. The host succession has been deformed into a pile of stacked clastic-detrital and schist formations developed along the Contendas-Mirante-Jacobina lineament, a 500 km long composite sinistral wrench-overthrust fault system reactivated during the Transamazonian Orogeny. This structure is located close to the contact between of the Palaeo- to Mesoarchaean Gavião Block and the Palaeoproterozoic reworked Itabuna-Salvador-Curaçá belts to its east, separating the former from the Mesoarchaean Serrinha Block further to the east. At least five successive stages are identified in the westward progradation of the basin, wherein bedding-parallel strike-slip thrusts and prograde metamorphism indicate progressive pulses of the Transamazonian orogeny.
Old basement rocks accompanied by 3.4 to 3.2 Ga Palaeoarchaean meta-volcano-sedimentary sequences composed of bimodal mafic to felsic volcanic-sedimentary and sub-volcanic rocks are exposed to the west of Jacobina, towards the eastern margin of the Gavião Block. These magmatic rocks are located on the western margin of a rift that evolved into the passive margin Jacobina-Umburanas Sea that extended to the east. Quartzites and conglomerates containing detrital zircons with a relatively narrow age range of from 3.4 to 3.2 Ga were deposited in this sea (U-Pb; Teles et al., 2014), along with pelites, and iron and manganese oxide formations formed in an oxidising regime. The deepest part of the sea contains 3.2 Ga 'ocean floor' pillow-lava basalts (Teles, 2013) whilst 3.296 Ga ultramafic intrusions occur within the basement Gavião Block (e.g., Barbosa et al., 2021). The un-eroded remnant basin has a >180 km length and hosts the quartzite sequence in which the gold-uranium-pyrite bearing Jacobina quartz-pebble conglomerates are intercalated. These rocks are structurally interleaved with i). the ~2595±21 Ma (U-Pb zircon; Spreafico et al., 2019) Mundo Novo Greenstone Belt, formed along the reactivated margin of the Gavião Block; and ii). the Saúde Complex which includes silici-clastics rocks that are lithologically similar to those of the Jacobina Group, but contain abundant 2.20 to 2.06 Ga and 2.68 to 2.50 Ga detrital zircons. The Saúde Complex was deposited in a transtensional pull apart basin along the reactivated Contendas-Mirante-Jacobina lineament during the Paleoproterozoic, prior to the final continent-continent collision between the Gavião, Serrinha and Jequié blocks. The inclusion of these three sequences into the Jacobina Group have previously been interpreted to indicate a Palaeoproterozoic age for the Jacobina conglomerates, although detailed work by Spreafico et al. (2019), reinforced by Barbosa et al. (2021), indicate the three sequences represent separate, structurally juxtaposed depositional/magmatic events in the Palaeoarchaean, Neoarchaean and Palaeoproterozoic, controlled by the long-lived Contendas-Mirante-Jacobina lineament. The latter is a north-south, ~600 km long linear tectonic structure that represents a major sinistral and west vergent composite thrust zone (Zincone and Oliveira, 2017). The structural interleaving and juxtaposition took place during the approach and eventual continent-continent collision between the Gavião, Serrinha and Jequié blocks in two pulses during the Neoarchaean and Palaeoproterozoic (Rhyacian).
Mafic to ultramafic dykes and granite stocks cross-cut the lithologies of the Jacobina Group. Conglomerates and chaotic breccia layers occur within several formations and mark intervals of tectonic instability that were accompanied by erosion of the earlier stages of basin development. The economic gold-bearing clastic sediments are conglomerates and minor quartzites which were deposited during the fourth stage of basin development.
The principal mineralised units within the Jacobina Group are described by Oram (1975), Minter (1975), Strydom and Minter (1976), Couto et al. (1978), and Molinari t al. (1986) and are applied at the mine in 2020 (Soares, et al., 2020) as follows:
Serra do Córrego Formation - a suite of interbedded quartzites and lesser auriferous conglomerates that forms the western ridge of the Serra da Jacobina, and is exposed over a strike length of ~90 km. It comprises an interbedded sequence of orthoquartzite and oligomictic conglomerate units that together vary in total thickness from 500 to 1000 m. Conglomerate pebbles comprise polycrystalline quartz with rare, fine-grained, fuchsite- and rutile-bearing quartzite. They are set in a matrix of quartz, sericite and fuchsite with detrital zircon, chrome-free rutile, tourmaline and chromite grains (Ledru et al., 1964). It is divided into three units:
• Lower Conglomerate, 40 to 200 m thick, outcropping along the lower parts of the western slopes of the Serra do Córrego, Morro do Cuscuz, and Morro do Vento areas and is composed of interbedded quartzite, pebbly quartzite and conglomerate units. The reef zones comprises oligomictic conglomerates that are interbedded with orthoquartzite. Pebble sizes range from 35 to 60 mm in diameter. This unit hosts the gold deposits of the Basal and the Main reefs.
• Intermediate Quartzite, 130 to 425 m thick, which is primarily composed of orthoquartzite with little or no conglomerate. The upper part of this unit is characterised by a distinct horizon, the 'marker schist', a highly sheared quartz-sericite-chlorite-andalusite schist.
• Upper Conglomerate, 120 to 400 m thick, comprising quartzite and pebbly quartzite interbedded with a number of conglomerate bands. The reef zones comprise interbedded conglomerate and orthoquartzite beds with pebble sizes ranging from 50 mm at Canavieiras in the north to 100 mm at the João Belo Mine in the south. The Upper Conglomerate Unit hosts the main gold orebodies of the Canavieiras, Morro do Vento, João Belo and Serra do Córrego mineralised areas.
Based on isopachs and pebble size data, Oram (1975), Minter (1975) and Strydom and Minter (1976) concluded that the paleoslope during deposition of the Serra do Córrego Formation sloped to the west, with a westerly palaeo-current direction indicated by the vector data. It is interpreted to have drained a source area to the east and deposited these sediments in a fluvial environment.
Rio do Ouro Formation, which is mostly composed of pure, fine-grained to medium-grained quartzite which can be either white, grey or light green. It contains subordinate calcareous pelitic rocks that are intercalated with the various quartzite beds. This formation is interpreted to mark a transition from the fluvial sedimentary environment of the Serra do Córrego Formation to a shallow marine, intertidal depositional environment. This change in depositional regime is implied by a change in the paleocurrent patterns as indicated by ripple marks, small-scale cross-bedding, and larger-scale herringbone cross-bedded features. The transition from the Serra do Córrego Formation to the Rio do Ouro Formation is marked by the presence of conglomerate units with limited lateral continuity. These locally developed conglomerate beds occur at the base of the Rio do Ouro Formation.
The upper unit is variously described as the Cruz das Almas, Serra do Meio, and the Serra da Paciência Formations. The Cruz das Almas Formation is >2100 m thick, is made up of pelitic schists with conspicuous porphyroblasts of andalusite and garnet, well bedded micaceous quartzites and minor conglomerate.
This sequence contains four zones of conglomerate development, namely a basal conglomerate at the base of the Serro do Córrego Formation, another ~150 m thick zone in the same formation, as much as 100 m above the base; a middle ~320 m thick zone also in the upper parts of the same formation, up to 300 to 500 m above the basement; and the top 20 m thick zone at the bottom of the Rio do Ouro Formation, which is up to 900 m above the basement.
The best mineralisation is found within the Main Reef in the second conglomerate zone ~150 m above the base, and in two intervals, the Joao Belo/Morro do Vento/Cuz-Cuz reefs and the Canavieras Reef, both of which are in the lower part of the middle zone. Virtually all of the conglomerates in the four zones carry very fine Au throughout, averaging around 0.5 g/t from 1000 samples. The uranium content is proportional to the Au grade. The basal conglomerate contains the Basal Reef which is around 4 m thick, has a strike extent of 300 m and contains up to 4.5 g/t Au.
The Main Reef has a good continuity over a strike length of >3 km. It occurs within an ~150 m thick package that comprises a massive, pyritic but barren, well rounded, well packed quartz-pebble conglomerate, a succeeding quartzite containing mineralised conglomerates of the Main Reef and another barren coarse pebble conglomerate at the top. The Main Reef itself has a thickness of 2 to 3 m and an average grade of 5.7 g/t Au.
The middle zone in the upper parts of the Serra do Córrego Formation contains hundreds of conglomerate layers. Two important quartzites split the zone into three distinct conglomeratic units. The lower and middle units contain economically mineralised, tongue like lenses of conglomerates, while the upper is barren. The João Belo Reef in the lower conglomerate unit has a combined thickness of 6 to 10 m and a strike length of 700 m containing 2.8 g/t Au. The other deposits in this same conglomerate unit, the Morro do Vento and Cuz-Cuz reefs are 1 to 2 m thick and grade from 4 to 6 g/t Au, with local enrichments in the upper 0.5 m. The Canavieras Reef in the middle conglomerate unit is a 0.5 to 2 m thick pyritic conglomerate with quartzite interbeds and grades of around 8 g/t Au.
The mountains of the Serra da Jacobina are bordered by deep longitudinal valleys that often correspond to weathered pre- to syn-tectonic mafic to ultramafic sills and dykes. These intrusives, which include dark green peridotite and pyroxenite, develop a brownish staining where weathered (Teixeira et al., 2001). Deformation and metamorphism, coupled with hydrothermal alteration, have apparently transformed these rocks into fine-grained schists containing talc, serpentine, chlorite, tremolite and carbonate (Teixeira et al., 2001). In the deposit area they were emplaced along both north- and east-trending structures, an affected and reacted with the host rocks (quartzite and conglomerates of the Serra do Córrego and Rio do Ouro formations) to produce metre-scale alteration zones in the adjacent hosts. The ultramafic rocks vary texturally from aphanitic borders to a medium to coarse-grained core with typical intrusive textures. The age of these intrusives is uncertain.
A variety of deformation styles are recognised within the Jacobina Group and adjacent Archaean rocks, along and across the northern 50 km section of the north-south Contendas-Mirante-Jacobina lineament. The interpreted Palaeoproterozoic continent-continent collision, as detailed above, resulted in a strong west vergent event that produced a series of strong thrusts, oblique sinistral-reverse faults, and both tight and open regional folds. In the west, the Jacobina Group is thrust westward over the Jacobina Fault, a major thrust separating it from the tectonically underlying Archaean Mairi Complex, Campo Formoso Mafic-Ultramafic Complex, and late- to post-tectonic granitic Miguel Calmon-Itapicurú, Mirangaba-Carnaíba and Campo Formoso intrusions. The structural setting progresses eastwards, from a reclined thrust setting to become a more upright regime comprising a series of steeply east-dipping blocks, bounded by east-dipping subparallel reverse faults. The regional compression associated with the development of the Itabuna-Salvador-Curaçá fold belt to the east of the Gavião Block, led to the development of a series of ductile shear zones and brittle faults, the main elements of which include a set of north-trending, sinistral strike-slip faults, east-trending, dextral strike-slip faults, and NW-trending shear zones with a sinistral sense of movement. These post-mineralisation structures displaced and offset the various gold-bearing zones.
The Serra do Córrego Formation outcrops on the western side of the Jacobina Range, where it forms part of an extensive homocline that dips consistently at 50 to 70°E and youngs to the east, as indicated by ripple marks and cross-bedding. This orientation is interpreted to be the result of tilting during the intrusion of the late- to post-tectonic Mirangaba-Carnaíba granite (Soares, et al., 2020).
Gold mineralisation in the Jacobina district is distributed over a 40 km interval that extends from Campo Limpo, in the south, to Santa Cruz do Coqueiro, in the north. This mineralisation almost exclusively occurs within the matrix of the conglomerates, including that at the Canavieiras, Morro do Vento, João Belo and Serra Branca deposits as well as numerous other minor occurrences. The host conglomerates of the Jacobina Group contain detrital zircons that range between ages of 3.4 to 3.2 Ga (U-Pb zircon, Teleset al., 2014). The deposit was deformed and overprinted by hydrothermal alteration associated with a 1.9 Ga orogenic event (Ledru et al., 1997) that generated pervasive silicification, chrome-sericite (fuchsite) alteration and some remobilisation of gold in fractures and faults, which represents a second minor style of gold mineralisation.
These two styles of mineralisation may be summarised as follows, after Texeira et al. (2001):
• Conglomerate-hosted gold mineralisation, which occurs as very fine, typically 20 to 50 µm grains of native gold, hosted in the matrix of the conglomerates, with no other significant associated elements. Detailed studies of the reef chemistry show only very minor enrichment in iron, titanium and uranium in some reefs associated with the occurrence of rounded grains of uraninite, ilmenite and rutile. Gold mineralisation is rarely found in the pebbles, other than in fractures. The interbedded quartzite units also host gold mineralisation but almost exclusively along fractures, particularly near late mafic dykes.
A steeply dipping, north-south striking ultramafic dyke subdivides the deposit area into West and East blocks. All mineralised reefs outcropping on the western margin of the Serra do Córrego Formation to its west classed as being in the West Block, whilst their down-dip extensions to its east (e.g., the Canavieiras zones) are considered to belong to the East Block.
The most significant past production has come from the Basal and Main reefs of the Lower Conglomerate Unit and the lower part of the Upper Conglomerate Unit. However, only certain reefs within particular lithological units are gold-bearing, whilst other nearby sub-parallel reefs with similar sedimentary features may not be gold-bearing. There is also considerable local lateral variation in grade within particular reefs, e.g., the Main and Basal reefs are well mineralised in the Morro do Vento Sector but are essentially barren to sub-economic in the João Belo and Canavieiras sectors. Never-the-less, the overall average grade, based on production records, is very consistent, both along strike and down dip within individual ore shoots. Sections through an example, the João Belo Zone, show reefs paralleling the stratigraphy which dips consistently at 50 to 70°E, with some local flattening. Cross-bedding and ripple marks indicate that the sequence youngs upwards, i.e., stratigraphic tops are towards the east. The principal characteristics of the main gold-mineralised reefs at Jacobina have been summarised by Soares, et al. (2020), from the base upwards for each zone, as follows:
- Morro do Vento Zone
Basal Reef - strike length of ~1600 m, thickness of 3 to 10 m, averages 4 g/t Au, with small to medium pebbles, and enrichment of gold at its upper and lower sections;
Footwall Reef - strike length of ~3000 m, thickness of 0.2 to 6 m, averages 2.4 g/t Au, and is pyritic, with small to medium pebble conglomerate beds;
Main Reef - strike length of ~3000 m, thickness of 12 m, averaging 6 g/t Au, and is pyritic, made up of 0.1 to 3 m thick beds of small to medium pebble conglomerate beds. It comprises three channels of deposition, dislocated by faulting;
Hangingwall Reef - strike length of ~3000 m, thickness of 1 to 6 m, averages 2.4 g/t Au, with large to medium sized pebbles;
LU (Upper) Reef - strike length of ~1700 m, thickness of 3 to 10 m, averages 2.4 g/t Au, with medium to large pebbles;
MU (Upper) Reef - strike length of ~1700 m, thickness of 3 to 10 m, averages 2.0 g/t Au, with medium to small pebbles;
LVLPC Reef - strike length of ~400 m, thickness of 2 m, averages 4.8 g/t Au, with large to very large pebbles, but only locally mineralised.
- Canavieiras Zone
LU Reef - strike length of ≥400 m, thickness of 1 to 10 m, averages 2.2 g/t Au, and is a pyritic, large pebble conglomerate;
MU Reef - strike length of ≥400 m, thickness of 10 to 25 m, averages 3.2 g/t Au, and is a pyritic, medium to large pebble conglomerate;
Piritoso Reef - strike length of ≥600 m, thickness of 1 to 3 m, averages 9.5 g/t Au, composed of medium size pebbles with abundant pyrite;
Liberino Reef - strike length of ≥600 m, thickness of 1 to 3 m, averages 6.1 g/t Au, found 10 m above the Piritoso Reef, with medium to large pebbles;
LVL Reef - strike length of ~2600 m, thickness of 0.5 to 5 m, averages 2.6 g/t Au, with large to very large pebbles;
MSPC Reef - strike length of ~800 m, thickness of 2 to 4 m, averages 4.4 g/t Au, with medium size pebbles and abundant pyrite;
Holandez Reef - strike length of ≥600 m, thickness of up to 30 m, made up of 0.9 to 6 m thick beds, averages 1.7 g/t Au, large to medium pebbles;
Maneira Reef - strike length of ≥600 m, thickness of up to 70 m, made up of 0.4 to 7 m thick beds, averages 1.7 g/t Au, large to very large pebbles.
- João Belo North Zone
MPC Reef - strike length of ≥1000 m, thickness of 1 to 4 m, averages 3.6 g/t Au, with medium sized pebbles that locally contain gold values;
LMPC Reef - strike length of ≥1000 m, thickness of 10 to 25 m, averages 2.2 g/t Au, with large to medium pebbles;
LVLPC Reef - strike length of ≥1000 m, thickness of 1 to 3 m, averages 4.4 g/t Au, with large to very large pebbles;
• Post-depositional gold-bearing stockwork, shear zones, and associated extensional quartz veins related to semi-concordant shear zones hosted by quartzites, andalusite-graphite-quartz schists, and locally, conglomerates of the Rio do Ouro Formation. It is accompanied by hydrothermal alteration that principally comprises silica, sericite, chlorite and pyrite (locally with chalcopyrite), and local tourmaline. Volumetrically, this style of gold mineralisation is only a very minor component at Jacobina and has not contributed significantly to the mineral resource. Ultramafic and mafic rocks also host mineralisation in narrow shear zones that are up to 4 m thick within north-south oriented ultramafic sills and dykes. These zones are proximal to the footwall and hangingwall contacts with the hosting quartzite and conglomerate units of the Serra do Córrego, Rio do Ouro and Serra da Paciência Formations, and are characterised by gold-bearing quartz veins and/or stockwork. The main associated hydrothermal alteration includes silica, fuchsite, pyrite and sericite, with local tourmaline. Again, this style of mineralisation does not contribute significantly to the mineral resource at Jacobina.
The late overprinting hydrothermal alteration event at the Jacobina consists of pyrite, pyrrhotite, quartz, chrome-sericite (fuchsite), chrome-rutile and chrome-tourmaline. The chromium-rich nature of this alteration assemblage is attributed to leaching of the mafic-ultramafic intrusive rock by circulating hydrothermal fluids.
Teixeira et al. (2010) argue that, despite the bulk of the gold being interstitial to the matrix of Palaeoarchaean quartz pebble conglomerates, the presence of structurally controlled hydrothermal mineralisation, and the occurrence of gold also in quartzites and mafic and ultramafic rocks, supports an epigenetic origin for the mineralisation. They suggest gold mineralisation was an integral part of the tectonothermal event responsible for the inversion of the Jacobina Basin. The main thrust and strike-slip events related to this inversion took place at 1940 to 1910 Ma, as indicated by Ar-Ar cooling ages of synkinematic biotite, muscovite and fuchsite that accompanies mineralisation (Ledru et al.,1997)
Reserves and resources at 31 December, 2010 (Yamana Gold website) were:
Proven + probable reserve - 20.96 Mt @ 2.48 g/t Au for 52.0 t Au; plus
Measured + indicated resource - 17.14 Mt @ 3.02 g/t Au for 51.7 t Au; plus
Inferred resource - 13.56 Mt @ 2.97 g/t Au for 40.2 t Au
Remaining NI 43-101 Compliant Ore Reserves and Mineral Resources at 31 December, 2019 (Yamana Gold NI 43-101 Technical Report, 2020) were:
Proven + probable reserve - 34.176 Mt @ 2.27 g/t Au for 77.5 t Au;
Measured + indicated resource - 42.47 Mt @ 2.26 g/t Au for 96 t Au;
Inferred resource - 18.528 Mt @ 2.36 g/t Au for 43.7 t Au.
NOTE: Mineral Resources are exclusive of Ore Reserves
The information in this summary is largely drawn from: de Souza Soares, E., Garcia Lopes, R., Marsden, H., Vasquez, L. and Iturralde, C., 2020 - Jacobina Gold Mine, Bahia State, Brazil; an NI 43-101 Technical Report prepared for Yamana Gold Inc., 205p..
The most recent source geological information used to prepare this decription was dated: 2020.
Record last updated: 18/1/2022
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Bateman J D, 1958 - Uranium-bearing auriferous reefs at Jacobina, Brazil : in Econ. Geol. v.53 pp. 417-425
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Garayp, E. and Frimmel, H.E., 2024 - A modified paleoplacer model for the metaconglomerate-hosted gold deposits at Jacobina, Brazil: in Mineralium Deposita v.59, pp. 627-654. doi.org/10.1007/s00126-023-01220-9.
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Gross W H, 1968 - Evidence for a modified placer origin for auriferous conglomerates, Canavieiras Mine, Jacobina, Brazil : in Econ. Geol. v.63 pp. 271-276
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Milesi, J.P., Ledru, P., Marcoux, E., Mougeot, R., Johan, V., Lerouge, C., Sabate, P., Bailly, L., Respaut, J.P. and Skipwith, P., 2002 - The Jacobina Paleoproterozoic gold-bearing conglomerates, Bahia, Brazil: A hydrothermal shear-reservoir model: in Ore Geology Reviews v.19, pp. 95-136.
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Teixeir, J.B.G., Silva, M.G., Misi, A., Cruz, S.C.P. and Sa, J.H.S., 2010 - Geotectonic setting and metallogeny of the northern Sao Francisco craton, Bahia, Brazil: in J. of South American Earth Sciences v.30, pp. 71-83.
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Teixeira J B G, Souza J A B, Silva M G, Leite C M M, Barbosa J S F, Coelho C E S, Abram M B, Conceicao Filho V M and Iyer S S 2001 - Gold mineralization in the Serra de Jacobina region, Bahia Brazil: tectonic framework and metallogenesis: in Mineralium Deposita v36 pp 332-344
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Teixeira, J.B.G., Misi, A., da Silva, M.G. and Brito, R.S.C., 2019 - Reconstruction of Precambrian terranes of Northeastern Brazil along Cambrian strike-slip faults: a new model of geodynamic evolution and gold metallogeny in the State of Bahia: in Brazilian Journal of Geology v.49, 21p. doi: 10.1590/2317-4889201920190009
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Teles, G., Chemale, F. and de Oliveira, C.G., 2015 - Paleoarchean record of the detrital pyrite-bearing, Jacobina Au-Udeposits, Bahia, Brazil: in Precambrian Research v.256, pp. 289-313.
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Teles, G.S., Chemale Jr., F., Avila, J.N., Ireland, T.R., Dias, A.N.C., Cruz, D.C.F. and Constantino, C.J.L., 2020 - Textural and geochemical investigation of pyrite in Jacobina Basin, Sao Francisco Craton, Brazil: Implications for paleoenvironmental conditions and formation of pre-GOE metaconglomerate-hosted Au-(U) deposits: in Geochimica et Cosmochimica Acta v.273, pp. 331-353.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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