No. Registros Solicitud 1 5614 colombia

DE - DESCRIPTORS: Bogota-Basin; C-13-C-12; carbon-; Cenozoic-; Colombia-; forests-; grasslands-; Holocene-; isotope-ratios; isotopes-; metabolism-; mineral-composition; paleoclimatology-; paleoenvironment-; Paleosols-; photochemistry-; photosynthesis-; Plantae-; Pleistocene-; Quaternary-; soil-profiles; soils-; South-America; stable-isotopes; tropical-environment; weathering-

CC - CATEGORY CODES: 24-Quaternary-geology; 02D-Isotope-geochemistry

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N043000; N053000; LONG: W0733000; W0743000.

IL - ILLUSTRATION: Refs: 46; illus. incl. 1 table, geol. sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0277-3791

CO - CODEN: #51137

AN - ACCESSION NUMBER: 2002-061728

UD - UPDATE CODE: 200220

Registro 535 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Transpressive tectonics during the Ottawan Orogeny; evidence from the Dana Hill metagabbro body, NW Adirondack Mtns., New York State.

AU - AUTHORS: Fruchey-Ben-L; Goergen-Eric-T; Johnson-Eric-L

AF - AUTHOR AFFILIATION: University of Wyoming, Department of Geology and Geophysics, Laramie, WY, United States

BK - BOOK TITLE: In: Geological Society of America, Northeastern Section, 36th annual meeting.

BA - BOOK AUTHORS: Anonymous

SO - SOURCE: Abstracts with Programs - Geological Society of America. 33; 1, Pages 80. 2001.

PB - PUBLISHER: Geological Society of America (GSA). Boulder, CO, United States. 2001.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

CN - CONFERENCE INFORMATION: Geological Society of America, Northeastern Section, 36th annual meeting. Burlington, VT, United States. March 12-14, 2001.

LA - LANGUAGE: English

AB - ABSTRACT: The Dana Hill Metagabbro Body (DHMG) is a small (5X1.5 km) gabbroic intrusion located along the boundary between the Adirondack highlands (Central Granulite Terrain CGT) and lowlands (Central Metasedimentary Belt CMB). The DHMG is located within the Carthage-Colton Shear Zone (CCSZ). Petrologic, structural, and geochronologic evidence indicates that the DHMG was multiply deformed and that deformation took place under amphibolite to granulite conditions syn- to post peak Ottawan Orogeny (1020 Mya). The shallow plunge on stretching lineations for granulite facies shear zones in the DHMG indicate that the early deformation/recrystallization events record predominately strike-slip motions along the CCSZ and that the structural level did not radically change during these shearing events. In short, early movements along the CCSZ were not caused by unroofing of the orogen, but rather by potentially large-scale, right-lateral strike-slip movements. Later events (shearing, folding and brecciation) span a wide range of conditions terminating with brecciation at greenschist facies conditions. These temporally later events may record dip-slip movements occurring as late as 945 Ma that eventually bring the CMB and CGT to a common structural level. In this model, the CMB and CGT terranes must have been laterally and vertically separated during the Ottawan Orogeny. The lateral (along strike) separation of the CGT and CMB may have been of great enough magnitude to allow these two terranes to undergo very different P-T-t paths during the Ottawan Orogeny without the need to invoke an intervening ocean basin. The tectonic scenario for the CGT during the Ottawan Orogeny is similar to the transpressive environment envisioned for the emplacement of the widely distributed Wrangellia and Cache Creek Terranes in western North America. The recognition of large scale strike-slip movements along shear zones during the Grenville (Ottawan) may shed light on the relative motions between CGT rocks of the Adirondack Highlands and Morin Terrane with other Grenville-aged CGT slices like the Oaxacan Complex in Mexico and Garzon Massif in Columbia.

DE - DESCRIPTORS: Adirondack-Mountains; amphibolite-facies; brecciation-; Cache-Creek-Terrane; Canadian-Shield; Carthage-Colton-shear-zone; Central-Granulite-Terrain; Central-Metasedimentary-Belt; Colombia-; Dana-Hill-metagabbro-body; deformation-; emplacement-; facies-; faults-; folds-; gabbros-; Garzon-Massif; granulite-facies; greenschist-facies; Grenville-Province; igneous-rocks; intrusions-; lateral-faults; metamorphic-rocks; Mexico-; Morin-Terrane; New-York; North-America; Oaxacan-Complex; Ottawan-Orogeny; P-T-t-paths; plutonic-rocks; right-lateral-faults; shear-; South-America; strike-slip-faults; transpression-; United-States; Wrangellia-

CC - CATEGORY CODES: 16-Structural-geology

DT - DOCUMENT TYPE: Abstract; Serial; Conference-Document

BL - BIB LEVEL: Analytic

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

IS - ISSN: 0016-7592

CO - CODEN: GAAPBC

AN - ACCESSION NUMBER: 2002-061200

UD - UPDATE CODE: 200220

Registro 536 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: The style of subduction of the Nazca Plate and a tectonic model for northwestern South America.

AU - AUTHORS: Hincapie-Jaime-O; Doser-Diane-I

AF - AUTHOR AFFILIATION: University of Texas at El Paso, Department of Geological Sciences, El Paso, TX, United States

BK - BOOK TITLE: In: AGU 1999 fall meeting.

BA - BOOK AUTHORS: Anonymous

SO - SOURCE: Eos, Transactions, American Geophysical Union. 80; 46, Suppl., Pages 650. 1999.

PB - PUBLISHER: American Geophysical Union. Washington, DC, United States. 1999.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 1999

CN - CONFERENCE INFORMATION: American Geophysical Union 1999 fall meeting. San Francisco, CA, United States. Dec. 13-17, 1999.

LA - LANGUAGE: English

DE - DESCRIPTORS: Andes-; Caribbean-Plate; Caribbean-region; Colombia-; faults-; mantle-; microplates-; models-; Nazca-Plate; neotectonics-; northwestern-South-America; overthrust-faults; Panama-Plate; Pizarro-seismic-zone; plate-tectonics; seismicity-; shorelines-; slabs-; South-America; subduction-; systems-; tectonics-; triple-junctions; volcanism-

CC - CATEGORY CODES: 18-Solid-earth-geophysics; 19-Seismology

DT - DOCUMENT TYPE: Abstract; Serial; Conference-Document

BL - BIB LEVEL: Analytic

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0096-3941

CO - CODEN: EOSTAJ

AN - ACCESSION NUMBER: 2002-059330

UD - UPDATE CODE: 200219

Registro 537 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: The design and construction of Porce II RCC dam in Colombia.

AU - AUTHORS: Tejada-L-C; Villegas-F; Dunstan-M-R-H; Hoyos-F

AF - AUTHOR AFFILIATION: Integral, COL, Colombia

SO - SOURCE: International Journal on Hydropower and Dams. 8; 3, Pages 51-57. 2001.

PB - PUBLISHER: Aqua-Media International. Sutton, United Kingdom. 2001.

CP - COUNTRY OF PUBLICATION: United-Kingdom

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: Porce II, the largest RCC dam in South America, has recently been completed in Colombia. This article reviews the design and construction of the dam, together with the performance up to and soon after impounding.

DE - DESCRIPTORS: Colombia-; construction-; dams-; design-; optimization-; Porce-II-Project; seepage-; South-America

CC - CATEGORY CODES: 30-Engineering-geology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 1; illus. incl. sect., 3 tables, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 1352-2523

AN - ACCESSION NUMBER: 2002-055277

UD - UPDATE CODE: 200218

Registro 538 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Q (sub Lg) tomography in Colombia.

AU - AUTHORS: Ojeda-Anibal; Ottemoeller-Lars

AF - AUTHOR AFFILIATION: University of Bergen, Institute of Solid Earth Physics, Bergen, Norway

SO - SOURCE: Physics of the Earth and Planetary Interiors. 130; 3-4, Pages 253-270. 2002.

PB - PUBLISHER: Elsevier. Amsterdam, Netherlands. 2002.

CP - COUNTRY OF PUBLICATION: Netherlands

PY - PUBLICATION YEAR: 2002

LA - LANGUAGE: English

AB - ABSTRACT: The crustal attenuation of Lg waves in Colombia was estimated and analyzed using local seismological data from the National Seismological Network of Colombia (RSNC). The selected dataset comprises 510 crustal earthquakes with a total of 2928 ray paths. This large dataset allowed us to invert for a regional average of Q (sub Lg) , tomographic images for Colombia, and simultaneously, source size for each event and site term at the seismological stations. The computed regional average for Q (sub Lg) in the frequency band 0.5-5.0 Hz was found to agree with the previously reported values in neighboring regions. In order to resolve the lateral variation in the attenuation of Lg waves in the crust, independent tomographic inversions for 26 frequencies between 0.5 and 5.0 Hz were conducted. The resulting maps confirm that heterogeneities in the crust exist and that they are related to the large-scale tectonic features in the country. The highest attenuation in the region is linked to the presence of active volcanic arcs, where the crust is weakened by partial melting. Relatively high attenuation is also found in zones where the crust is composed of accreted oceanic rocks and in regions with near-surface low-velocity sedimentary layers.

DE - DESCRIPTORS: attenuation-; Colombia-; continental-crust; crust-; elastic-waves; geophysical-methods; geophysical-surveys; guided-waves; Lg-waves; seismic-methods; seismic-waves; South-America; surface-waves; surveys-; tectonics-; tomography-

CC - CATEGORY CODES: 18-Solid-earth-geophysics

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 42; illus. incl. 1 table, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0031-9201

CO - CODEN: PEPIAM

AN - ACCESSION NUMBER: 2002-054222

UD - UPDATE CODE: 200218

Registro 539 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Sequential phosphorus extraction of a (super 33) P-labeled Oxisol under contrasting agricultural systems.

AU - AUTHORS: Buehler-S; Oberson-A; Rao-I-M; Friesen-D-K; Frossasrd-E

AF - AUTHOR AFFILIATION: Swiss Federal Institute of Technology (ETH), Institute of Plant Sciences, Lindau, Switzerland

SO - SOURCE: Soil Science Society of America Journal. 66; 3, Pages 868-877. 2002.

PB - PUBLISHER: Soil Science Society of America. Madison, WI, United States. 2002.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2002

LA - LANGUAGE: English

AB - ABSTRACT: Chemical sequential extraction is widely used to divide soil phosphorus (P) into different inorganic (P (sub i) ) and organic (P (sub o) ) fractions, but the assignment of these fractions to pools of differing plant availability, especially for low P tropical soils, is still matter of discussion. To improve this assignment, the effect of land-use systems and related P fertilizer inputs on size of P fractions and their isotopic exchangeability was investigated. A Colombian Oxisol, sampled from a long-term field experiment with contrasting management treatments, was labeled with carrier free (super 33) P and extracted after incubation times of 4 h, 1, and 2 wk. Phosphorus concentrations and (super 33) P recovery in fractions sequentially extracted with anion exchange resin (P (sub i) ), 0.5 M NaHCO (sub 3) (Bic-P (sub i) , Bic-P (sub o) ), 0.1 M NaOH (P (sub i) , P (sub o) ), hot concentrated HCl (P (sub i) , P (sub o) ), and residual P were measured for each incubation time. Resin-P (sub i) , Bic-P (sub i) , NaOH-P (sub i) , and hot HCl-P (sub i) were increased with P fertilization, with the highest increase for NaOH-P (sub i) . The recovery of (super 33) P in the treatments with annual P fertilization clearly exceeding P outputs indicate that resin-P (sub i) , Bic-P (sub i) , and NaOH-P (sub i) represented most of the exchangeable P. In these treatments, label P transformed with increasing incubation time from the resin to the Bic-P (sub i) and NaOH-P (sub i) fractions. The organic or recalcitrant inorganic fractions contained almost no exchangeable P. In contrast, in soils with low or no P fertilization, more than 14% of the (super 33) P was recovered in NaOH-P (sub o) and HCl-P (sub o) fractions 2 wk after labeling, showing that organic P dynamics are important when soil P (sub i) reserves are limited.

DE - DESCRIPTORS: agriculture-; bioavailability-; Carimagua-Columbia; Colombia-; fertilization-; inorganic-materials; isotope-exchange; isotopes-; Meta-Columbia; mineral-composition; organic-compounds; Oxisols-; P-33; phosphorus-; physicochemical-properties; radioactive-isotopes; sequential-extraction; soil-management; soils-; South-America; statistical-analysis; tropical-environment

CC - CATEGORY CODES: 02D-Isotope-geochemistry; 25-Soils

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N043000; N043000; LONG: W0711900; W0711900.

NN - ANNOTATION: Accessed on May 16, 2002.

IL - ILLUSTRATION: Refs: 68; illus. incl. 7 tables.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0361-5995

CO - CODEN: SSSJD4

UR - URL: (Full text) http://www.scijournals.org/; (Series) http://soil.scijournals.org/

AN - ACCESSION NUMBER: 2002-052017

UD - UPDATE CODE: 200217

XURL - URLs, etc : URL; URL-ITEM (UR)

Registro 540 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Les inclusions en double helice dans les emeraudes de Colombie

Translated Title: Double helix inclusions in Colombian emeralds.

AU - AUTHORS: Vuillet-P; Rotlewicz-J

AF - AUTHOR AFFILIATION: StarEmerald Colombia, Bogota, Colombia

SO - SOURCE: Revue de Gemmologie A.F.G.. 143; Pages 15-19. 2001.

PB - PUBLISHER: Association Francaise de Gemmologie. Paris, France. 2001.

CP - COUNTRY OF PUBLICATION: France

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: French

LS - LANGUAGE OF SUMMARY: English

DE - DESCRIPTORS: beryl-; Colombia-; emerald-; inclusions-; ring-silicates; silicates-; South-America

CC - CATEGORY CODES: 01B-Mineralogy-of-silicates

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 10

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France

IS - ISSN: 0398-9011

AN - ACCESSION NUMBER: 2002-051784

UD - UPDATE CODE: 200217

Registro 541 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: La composition isotopique de l'oxygene des emeraudes de la mine de La Pita

Translated Title: Oxygen isotope composition of emeralds from La Pita Mine.

AU - AUTHORS: Giuliani-G

AF - AUTHOR AFFILIATION: CRPG-CNRS, Vandoeuvre-les-Nancy, France

SO - SOURCE: Revue de Gemmologie A.F.G.. 143; Pages 13-14. 2001.

PB - PUBLISHER: Association Francaise de Gemmologie. Paris, France. 2001.

CP - COUNTRY OF PUBLICATION: France

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: French

DE - DESCRIPTORS: beryl-; chemical-composition; Colombia-; emerald-; isotope-ratios; isotopes-; La-Pita-Mine; mines-; O-18-O-16; oxygen-; ring-silicates; silicates-; South-America; stable-isotopes

CC - CATEGORY CODES: 02D-Isotope-geochemistry; 01B-Mineralogy-of-silicates

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 3

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France

IS - ISSN: 0398-9011

AN - ACCESSION NUMBER: 2002-051783

UD - UPDATE CODE: 200217

Registro 542 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Les nouvelles mines de La Pita (Colombie); 1 (super ere) partie

Translated Title: New mines of La Pita (Colombia); Part 1.

AU - AUTHORS: Michelou-J-C

SO - SOURCE: Revue de Gemmologie A.F.G.. 143; Pages 9-13. 2001.

PB - PUBLISHER: Association Francaise de Gemmologie. Paris, France. 2001.

CP - COUNTRY OF PUBLICATION: France

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: French

DE - DESCRIPTORS: beryl-; Colombia-; emerald-; gems-; La-Pita-Colombia; ring-silicates; silicates-; South-America

CC - CATEGORY CODES: 28A-Economic-geology,-geology-of-nonmetal-deposits

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France

IS - ISSN: 0398-9011

AN - ACCESSION NUMBER: 2002-051782

UD - UPDATE CODE: 200217

Registro 543 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: A simulation approach to validate petrophysical data from NMR imaging.

AU - AUTHORS: Zuluaga-Elizabeth; Majors-Paul-D; Peters-Ekwere-J

AF - AUTHOR AFFILIATION: U. Nacional de Colombia, Reservoir Laboratory, COL, Colombia

SO - SOURCE: SPE Journal. 7; 1, Pages 35-39. 2002.

PB - PUBLISHER: Society of Petroleum Engineers. Richardson, TX, United States. 2002.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2002

LA - LANGUAGE: English

AB - ABSTRACT: Nuclear magnetic resonance (NMR) imaging was used to map the 3D porosity and permeability distributions in heterogeneous sandstone cores under controlled laboratory conditions. The porosity and permeability distributions so obtained were used to numerically simulate first-contact miscible displacements in the cores. The spatial and temporal solvent concentrations from the numerical simulations were compared to those from imaging experiments in the cores in an effort to validate the porosity and permeability data. The results show that with calibration, useful 3D porosity and permeability distributions of heterogeneous cores can be derived from NMR imaging (NMRI).

DE - DESCRIPTORS: enhanced-recovery; hydraulic-fracturing; imagery-; NMR-spectra; numerical-models; permeability-; petrography-; petroleum-; petroleum-engineering; reservoir-properties; simulation-; spectra-

CC - CATEGORY CODES: 29A-Economic-geology,-geology-of-energy-sources

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 20; illus. incl. 4 tables.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 1086-055X

AN - ACCESSION NUMBER: 2002-050703

UD - UPDATE CODE: 200217

Registro 544 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Une coupe de la province volcanique Caraibe; premiers resultats de la campagne sismique CASIS 2

Translated Title: A transect of the Caribbean volcanic province; preliminary results of the CASIS 2 seismic survey.

AU - AUTHORS: Mauffret-Alain; Leroy-Sylvie; d-Acremont-Elia; Maillard-Agnes; Mercier-de-Lepinay-Bernard; Tadeu-dos-Reis-Antonio; Miller-Naghieb; Nercessian-Alexandre; Perez-Vega-Roberto; Perez-Diorys

AF - AUTHOR AFFILIATION: Universite de Paris VI, Paris, France

SO - SOURCE: Comptes Rendus de l'Academie des Sciences, Serie II. Sciences de la Terre et des Planetes. 333; 10, Pages 659-667. 2001.

PB - PUBLISHER: Elsevier. Paris, France. 2001.

CP - COUNTRY OF PUBLICATION: France

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: French

LS - LANGUAGE OF SUMMARY: English

AB - ABSTRACT: The eastwards motion of the Caribbean Plate is supposed to be related to a Cretaceous flip of subduction from east to west vergence. However, we do not observe on the seismic profiles recorded during the CASIS 2 cruise, any evidence of subduction beneath the Aves Ridge and Nicaragua Rise. The Aves volcanic arc was probably formed after the collision of the Caribbean volcanic plateau as shown by a wedge of volcanic-clastic sediments imaged by the seismic cruise CASIS 2. Recent left-lateral transtensional tectonics are observed in the lower Nicaragua Rise; the Colombia basin might have a motion towards the northeast relative to the rise.

DE - DESCRIPTORS: Atlantic-Ocean; Aves-Ridge; Caribbean-Plate; Caribbean-region; Caribbean-Sea; CASIS-2; clastic-sediments; Colombia-; Cretaceous-; geophysical-methods; geophysical-profiles; geophysical-surveys; island-arcs; Mesozoic-; movement-; Nicaragua-Rise; North-Atlantic; plate-tectonics; plateaus-; sediments-; seismic-methods; seismic-profiles; South-America; subduction-; surveys-; tectonics-; transtension-

CC - CATEGORY CODES: 20-Applied-geophysics

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 39

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France

IS - ISSN: 1251-8050

CO - CODEN: #03814

AN - ACCESSION NUMBER: 2002-050173

UD - UPDATE CODE: 200217

Registro 545 de 5614 - GeoRef : 2002-2004/12

TI - TITLE: Gem localities of the 1990s.

AU - AUTHORS: Shigley-James-E; Dirlam-Dona-M; Laurs-Brendan-M; Boehm-Edward-W; Bosshart-George; Larson-William-F

AF - AUTHOR AFFILIATION: Richard T. Liddicoat Library and Information Center, USA, United States

SO - SOURCE: Gems and Gemology. 36; 4, Pages 292-335. 2000.

PB - PUBLISHER: Gemological Institute of America. Santa Monica, CA, United States. 2000.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2000

LA - LANGUAGE: English

AB - ABSTRACT: The past decade saw growth in gem exploration, production, and marketing worldwide. Important colored stone-producing regions included: Southeast Asia (Myanmar, Thailand, and Vietnam), Africa (Tanzania, Kenya, Zimbabwe, Nigeria, and Namibia, as well as Madagascar), South America (Brazil and Colombia), central and southern Asia (Sri Lanka, India, Afghanistan, Pakistan, Russia, and China), and Australia. The major sources for diamonds were Australia, central and southern Africa (Botswana, South Africa, Namibia, Angola, and Zaire), and Russia (mainly in the Republic of Sakha), with exciting discoveries in northern Canada. Cultured pearls from French Polynesia, Australia, and China became increasingly important, as production from Japan declined. This article provides a comprehensive overview of those gem deposits that were either new or remained commercially significant in the last decade of the 20th century.

DE - DESCRIPTORS: Afghanistan-; Africa-; aquamarine-; Asia-; Australasia-; Australia-; beryl-; Botswana-; Brazil-; Burma-; Central-Africa; chain-silicates; China-; chrysoberyl-; Colombia-; Commonwealth-of-Independent-States; Congo-Democratic-Republic; demantoid-; diamonds-; East-Africa; emerald-; epidote-group; Far-East; fluorides-; framework-silicates; garnet-group; gems-; halides-; India-; Indian-Ocean-Islands; Indian-Peninsula; jade-; Kenya-; Madagascar-; mineral-exploration; mineral-localities; Namibia-; nesosilicates-; Nigeria-; opal-; orthosilicates-; oxides-; Pakistan-; pearls-; production-; quartz-crystal; ring-silicates; rubies-; Russian-Federation; sapphire-; silica-minerals; silicates-; sorosilicates-; South-Africa; South-America; Southeast-Asia; Southern-Africa; Sri-Lanka; Tanzania-; tanzanite-; Thailand-; topaz-; tourmaline-; Vietnam-; West-Africa; Zimbabwe-