Taken from Preface to the Geochemical Atlas of Eastern Bolivia.
Between 1976 and 1982, the Overseas Directorate of BGS, United Kingdom and the Geological Survey of Bolivia, Santa Cruz, carried out a major reconnaissance geological mapping, geochemical sampling and mineral exploration programme of that part of the Precambrian Brazilian Shield lying within eastern Bolivia. Previous geological work had been undertaken in the area, but this was the first time that a systematic and fully integrated survey had been attempted. The Project area is approximately 220 000 km2 and regional geochemical samples were collected from 8185 sites producing an overall sampling density of one sample per 27 km2 . Because of logistic problems it was impossible to sample certain inaccessible areas so the actual sampling density was one sample per 16 km2 for the 130 000 km2 effectively sampled. The geochemical samples were analysed in the Project laboratories in Santa Cruz and in the GEOBOL geochemical laboratories in La Paz. Uranium analyses were carried out by a commercial laboratory in the UK. The results of the Project are incorporated in 21 comprehensive reports in both English and Spanish. 12 describe the geology, geochemistry and mineral potential of the individual 1:250 000 map areas and the remainder are devoted to the geology and mineral potential of areas of special geological or economic interest.
The geology and mineral potential of the whole of the project area are summarised in:
Litherland M et al. 1986. The geology and mineral resources of the Bolivian Precambrian. British Geological Survey Overseas Memoir No. 9, BGS Keyworth, Nottingham, UK
The results of the regional geochemical survey are presented in:
Appleton J D and Llanos A. 1985. Geochemical Atlas of Eastern Bolivia. British Geological Survey, Keyworth, Nottingham, UK.
These results are presented as 22 single element 1:1 million scale, classed proportional symbol, point source data maps in which the symbols are overprinted on a simplified geological base map in order to facilitate rapid data interpretation. A 1:4 million scale moving average map based on a 4 x 4 km cell size and a 10 km search radius, printed alongside the symbol map, identifies the major regional variations. This combination of maps permits the identification of regional related to major variations of bedrock composition as well as single or clusters of anomalously high values that may be indicative of mineralisation.
Fields in database:
- Samptype: Sample type:- F = Stream Sediment, S = Soil
- Sampno: Unique sample identifier
- UTMZone: Universal Transverse Mercator Projection Zone number
- Easting: x co-ordinates as read from 1:100,000 field maps (1 grid unit = 1 metre but read to nearest 100 m)
- Northing: y co-ordinates as read from 1:100 000 field maps (1 grid unit = 1 metre but read to nearest 100 m)
- Rockcode: Catchment area rock type code:
Codes for Rockcode in the Projecto Precambrico dataset
Period or Era | Stratigraphic Unit | Code |
---|---|---|
Cretaceous | El Porton Group | CRE |
Jurassic – Cretaceous | Carbonatite complex | CAR |
Jurassic – Cretaceous | Alkaline igneous complexes | SYN, GTS |
Silurian – Devonian | San José and Santiago Groups | DEV |
Upper Proterozoic ? Cambrian | Boqui, Tucavaca and Murceilago Groups | BOQ, COA, COC |
Upper Proterozoic ? Cambrian | Huanchaka Dolerite Suite | BAS |
Middle Proterozoic | Sunsas Granites and granodiorites | GTO |
Middle Proterozoic: Rincón del Tigré | Mafic Rocks | BAS |
Igneous Complex | Ultramafic Rocks | UMA |
Middle Proterozoic | Sunsas and Vibosi Groups | SUN, TAB |
San Ignacio Alkaline complex (nordmarkite) | SYN | |
Middle | San Ignacio Post-kinematic Granite | PG, PGA, PGD, PGP, PGT, PGR |
Proterozoic | San Ignacio Syn-kinematic Granite | GTA, PGA, PGC, PGJ, PGL, PGO, PGV |
San Ignacio Granophyre Complexes | PGC, PGG, PGV | |
Middle Proterozoic | Basic and ultramafic igneous rocks in the San Ignacio Supergroup | BAS, PEB |
Middle Proterozoic | San Ignacio Supergroup | ESQ, NAR, PAJ, PCA, PDE, PLB, PNC, PNH, PPE, PSS |
Lower Proterozoic | Chiquitania Complex and Lomas Maneches Complex | CGC, GNS, PBE, PEN, PHG, PMG, PRP |
- Cover: Nature of superficial cover:- N = Not covered, L = Laterite, A = Alluvium and aeolian sands
- Area: Map sheet code for sample collection site
Area code | 1:250k Sheet name | Sheet number |
1 | Magdalena | SD20-2 + SD20-6 |
2 | Puerto Villazon | SD20-3 + SD20-7 |
3 | Huachi | SD20-10 |
4 | Perseverancia | SD20-11 |
5 | Huanchaca | SD20-8 + SD20-12 |
6 | Ascension | SD20-14 |
7 | Monte Verde | SD20-15 |
8 | Manomo | SD20-18 |
17xxx | Concepcion | SE20-2 + SE20-3 |
4200x | San Ignacio | SE20-4 |
47xxx | San Matias | SE21-1 + SE21-2 |
402015-25 | San Jose de Chiquitos | SE20-7 + SE20-8 |
57xxx | Santo Corazon | SE21-5 + SE21-9 |
67xxx-68xxx | Laguna Gaiba | SE21-6 + SE21-10 |
77xx | Velasco | project area largely in SD20-18 |
- x: x UTM Co-ordinates calculated on UTM Zone 20
- y: x UTM Co-ordinates calculated on UTM Zone 20
- Element field: chemical symbol plus method of analysis
- AAS atomic adsorption spectroscopy
- OES optical emission spectroscopy
- COL colorimetric
- DNA delayed neutron activation
- LOI % Loss of weight on ignition of sample at 450° C
- Phase: Phase of project (1 or 2)
Values in ppm assigned to samples below the limit of detection are:
ELEMENT | ELEMENT | ELEMENT | ELEMENT | ||||
---|---|---|---|---|---|---|---|
Ag | 0.5 | As | 2 | B | 18 | Ba | 56 |
Be | 1 | Co | 1 | Cr | 10 | Cu | 1 |
Fe | 100 | La | 32 | Li | 32 | Mo | 1 |
Mn | 10 | Nb | 10 | Ni | 1 | Pb | 3 |
Sn | 3 | Sr | 10 | U | 0.5 | Y | 10 |
Zn | 1 | Zr | 100 | LOI | 0.1% |
Absent data are indicated by -1.
All samples have UTM grid co-ordinates (UTM Zones 20 and 21) and have been standardised on the UTM Zone 20. The standardised data x/y co-ordinates are presented in the database as x and y.
Excel filename | EBOLIVIA.XLS |
CSV filename | EBOLIVIA.CSV |
DBF filename | EBOLIVIA.DBF |
Minimum Easting (x) (UTM20) | 367800 Long. -64.3° |
Maximum Easting (x) (UTM20) | 1079300 Long. -57.7° |
Minimum Northing (y) (UTM20) | 7967100 Lat. -18.4° |
Maximum Northing (y) (UTM20) | 8624100 Lat.- 12.4° |
Number of sites | 8132 (6912 sedts and 1220 soils) |
Average corrected sampling density | 1 per 16 km² |
Fraction used | -150 micron |
Elements by AAS (hot nitric acid extraction) | Ag, Co, Cu, Fe, Mn, Ni, Pb, Zn |
Elements determined colorimetrically (Gutzeit method) | As |
Elements determined by Delayed Neutron Activation (DNA) | U |
Elements by Optical Emission Spectroscopy (OES) | B, Ba, Be, Cr, La, Li, Mo, Nb, Sn, Sr, Y, Zr |
Reference to the CD-ROM should be as follows:
BGS (2007). Bolivia Regional Geochemical Survey CD-ROM: Proyecto Precàmbrico – Eastern Bolivia. Version 2.0. BGS International Regional Geochemistry CD-ROM Series, No. 3 Bolivia. British Geological Survey, Keyworth, Nottingham, UK
BGS work in Bolivia
Central enquiries
British Geological Survey
Keyworth Nottingham NG12 5GG
United Kingdom
Tel: +44 (0)115 936 3143
Fax: +44 (0)115 939 3276 Email: enquiries@bgs.ac.uk
Collaborating organisation: Bolivian Geological Survey
Director Ejecutivo
Servicio Nacional de Geologàa y Mineràa SerGeoMin
Calle Federico Zuazo 1673, Esquina Reyes Ortiz,
La Paz, Bolivia
Tel. (591-2) 2311373
readme.doc | Information file (in MS Word 2003 format) |
readme.pdf | Information file (in PDF format) |
ebolivia.csv | Geochemical results and locational data for stream sediments and soils in comma separated variable format, first row contains field names |
ebolivia.xls | Geochemical results and locational data for stream sediments and soils in MS Excel 2003 format, first row contains field names |
ebolivia.dbf | Geochemical results and locational data for stream sediments and soils in dBase III+ format |
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