Pub Date : 2021-09-02DOI: 10.32685/0120-1425/bol.geol.48.spl.1.2021.574
Ismael Enrique Moyano Nieto, Renato Cordani, Marcela Lara, Ó. Rojas, M. Puentes, D. Ospina, Hernán Arias, Ernesto Gómez, S. Torrado, A. Robayo, G. Prieto
The Servicio Geológico Colombiano has made available several airborne magnetometry and gamma-ray spectrometry datasets. The information was acquired in 15 blocks that cover approximately 520,000 square kilometers of Colombian territory, representing more than 850,000 linear kilometers of information. The data were collected along flight lines separated by 500 meters or 1000 meters, depending on the area, with sampling rates of 10 Hz (8 meters) and 1 Hz (80 meters) for the magnetometry and gamma-ray spectrometry data, respectively. The information is stored in 30 databases separated for each block and for each of the geophysical methods used. The Servicio Geológico Colombiano has provided a web portal that provides detailed specifications for each database and allows interested parties to see the terms and conditions to access the datasets and to check possible restrictions on access to information. To date, there is no geophysical database in Colombia with the coverage and resolution of these data sets, which will be very useful for geological research and research on potential mineral resources and to support geohazard monitoring, land-use planning and providing a baseline dataset for environmental monitoring.
{"title":"Magnetic and gamma-ray spectrometric airborne geophysical data for investigating potential mineral resources and generating geoscientific knowledge in Colombia","authors":"Ismael Enrique Moyano Nieto, Renato Cordani, Marcela Lara, Ó. Rojas, M. Puentes, D. Ospina, Hernán Arias, Ernesto Gómez, S. Torrado, A. Robayo, G. Prieto","doi":"10.32685/0120-1425/bol.geol.48.spl.1.2021.574","DOIUrl":"https://doi.org/10.32685/0120-1425/bol.geol.48.spl.1.2021.574","url":null,"abstract":"The Servicio Geológico Colombiano has made available several airborne magnetometry and gamma-ray spectrometry datasets. The information was acquired in 15 blocks that cover approximately 520,000 square kilometers of Colombian territory, representing more than 850,000 linear kilometers of information. The data were collected along flight lines separated by 500 meters or 1000 meters, depending on the area, with sampling rates of 10 Hz (8 meters) and 1 Hz (80 meters) for the magnetometry and gamma-ray spectrometry data, respectively. The information is stored in 30 databases separated for each block and for each of the geophysical methods used. The Servicio Geológico Colombiano has provided a web portal that provides detailed specifications for each database and allows interested parties to see the terms and conditions to access the datasets and to check possible restrictions on access to information. To date, there is no geophysical database in Colombia with the coverage and resolution of these data sets, which will be very useful for geological research and research on potential mineral resources and to support geohazard monitoring, land-use planning and providing a baseline dataset for environmental monitoring. ","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"153 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116724658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-12DOI: 10.32685/0120-1425/BOL.GEOL.48.1.2021.524
Anny Julieth Forero Ortega, Julián Andrés López Isaza, Nelson Ricardo López Herrera, Mario Andrés Cuéllar Cárdenas, Lina María Cetina Tarazona, Luis Miguel Aguirre Hoyos
The deformation registered in rocks in the field can be characterized based on the structures preserved in outcrops, which can related be to wide discontinuity zones named faults and shear zones. The geological-structural mapping and the geochronology of these tectonic structures are a topic of great interest not only for tectonic modeling but also for reconstruction of the geological evolution of the national territory. The methodology suggest for the analysis of faults and shear zones is based on eight steps, including: 1) definition of the geological context in which the structure was developed; 2) photointerpretation, image geoprocessing, and geological-structural mapping of the structural and lithological characteristics of the faults and shear zones; 3) petrographic analysis of field-oriented samples; 4) quantification of strain orientation and geometry through 3D finite strain analyses and quantification of non-coaxiliaty of deformation through vorticity analyses; 5) SEM-TEM-EBSD microanalysis; 6) quantification of the P-T conditions of deformation through phase-equilibria modeling or conventional geothermobarometry; 7) dating of syn-kinematic minerals phases and mylonitic rocks through Ar-Ar analyses, in order to determine the reactivation and deformation ages of the structure, respectively, as well as the implementation of the U-Pb technique in syn-kinematic calcite crystals developed in the fault planes; and 8) dating of geological elements adjacent to the structure, such as syn-kinematic intrusive bodies associated with the deformation event using zircon U-Pb dating, rocks hydrothermally altered through Ar-Ar method, and zircon and apatite fission-tracks dating of the blocks adjacent to the faults for determining exhumation ages.
{"title":"Geological-structural mapping and geocronology of shear zones: A methodological proposal","authors":"Anny Julieth Forero Ortega, Julián Andrés López Isaza, Nelson Ricardo López Herrera, Mario Andrés Cuéllar Cárdenas, Lina María Cetina Tarazona, Luis Miguel Aguirre Hoyos","doi":"10.32685/0120-1425/BOL.GEOL.48.1.2021.524","DOIUrl":"https://doi.org/10.32685/0120-1425/BOL.GEOL.48.1.2021.524","url":null,"abstract":"The deformation registered in rocks in the field can be characterized based on the structures preserved in outcrops, which can related be to wide discontinuity zones named faults and shear zones. The geological-structural mapping and the geochronology of these tectonic structures are a topic of great interest not only for tectonic modeling but also for reconstruction of the geological evolution of the national territory. The methodology suggest for the analysis of faults and shear zones is based on eight steps, including: 1) definition of the geological context in which the structure was developed; 2) photointerpretation, image geoprocessing, and geological-structural mapping of the structural and lithological characteristics of the faults and shear zones; 3) petrographic analysis of field-oriented samples; 4) quantification of strain orientation and geometry through 3D finite strain analyses and quantification of non-coaxiliaty of deformation through vorticity analyses; 5) SEM-TEM-EBSD microanalysis; 6) quantification of the P-T conditions of deformation through phase-equilibria modeling or conventional geothermobarometry; 7) dating of syn-kinematic minerals phases and mylonitic rocks through Ar-Ar analyses, in order to determine the reactivation and deformation ages of the structure, respectively, as well as the implementation of the U-Pb technique in syn-kinematic calcite crystals developed in the fault planes; and 8) dating of geological elements adjacent to the structure, such as syn-kinematic intrusive bodies associated with the deformation event using zircon U-Pb dating, rocks hydrothermally altered through Ar-Ar method, and zircon and apatite fission-tracks dating of the blocks adjacent to the faults for determining exhumation ages.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125195379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-12DOI: 10.32685/0120-1425/BOL.GEOL.48.1.2021.500
Felipe Arrubla Arango, Sergio Esteban Silva Sánchez
The Frontino-Morrogacho gold district is located on the western flank of the Western Cordillera, NW of Antioquia Province. Gold mineralizations in the area are spatially and genetically associated with the cooling of three mid- to late-Miocene age intrusive centers in the form of stocks and dikes (12-9 Ma): Cerro Frontino, La Horqueta and Morrogacho (El Cerro Igneous Complex). These composite magmatic pulses, with ultramafic to intermediate compositions, vary into diorite-, gabbro- and monzonitic-bearing phases. Mineralization in the complex is present as several structurally controlled fault veins, shear-related veins, sheeted quartz extension veins and quartz-carbonate tabular extension veins, with the development of swarms and nests of veins-veinlets, breccias and stockworks. Structures range from centimeter-wide individual veinlets to several meter-wide swarms of veins developed within broad mineralized structural corridors, with a metallic signature that consists of Au + Ag + Cu + Zn + Pb + As (± Te ± Bi ± Sb ± Hg ± W) assemblages. Veins are composed of multiple stages of mineralization, and the formation of these structures is enhanced by the presence of a local regime of extension and E-trending structures, including evidence of faults and shear zones with right-lateral displacement, which are likely involved in pluton emplacement and cooling. The ore mineralogy is composed of pyrrhotite, pyrite, chalcopyrite, sphalerite, galena and arsenopyrite assemblages formed in two or more mineralization stages, with complex Bi, Te, Sb and Hg mineral specimens associated with Au and Ag. Mineralized structures of the district present a preferential E-strike with dominant vertical to subvertical and occasional subhorizontal S-dips and secondary N- and NW-strikes that are steep to vertically E-dipping. The Frontino-Morrogacho Gold district presents characteristics related to the architecture, mineralogy and alteration of reduced (ilmenite-series) intrusion-related gold systems but is genetically associated with a parental oxidized magma source. The gold content is associated with three different families involving electrum, tellurides and alloys: gold rich (66 to 78% Au, 22 to 34% Ag), average (50 to 60% Au, 40 to 50% Ag) and silver rich (32 to 40% Au, 60 to 68% Ag). The formation of these bodies is associated with an N-S magmatic-metallogenic trend of Au-Ag-Cu deposits, which extend for more than 300 km along the Western Cordillera of Colombia. Similar plutonic suites span from the south of Chocó Province to the north of Antioquia Province, which indicates that the Frontino-Farallones-Botón arc can be proposed as an individual metallogenic belt.
{"title":"Geology of the Frontino-Morrogacho Gold Mining District and Metallogeny of the El Cerro Igneous Complex","authors":"Felipe Arrubla Arango, Sergio Esteban Silva Sánchez","doi":"10.32685/0120-1425/BOL.GEOL.48.1.2021.500","DOIUrl":"https://doi.org/10.32685/0120-1425/BOL.GEOL.48.1.2021.500","url":null,"abstract":"The Frontino-Morrogacho gold district is located on the western flank of the Western Cordillera, NW of Antioquia Province. Gold mineralizations in the area are spatially and genetically associated with the cooling of three mid- to late-Miocene age intrusive centers in the form of stocks and dikes (12-9 Ma): Cerro Frontino, La Horqueta and Morrogacho (El Cerro Igneous Complex). These composite magmatic pulses, with ultramafic to intermediate compositions, vary into diorite-, gabbro- and monzonitic-bearing phases. Mineralization in the complex is present as several structurally controlled fault veins, shear-related veins, sheeted quartz extension veins and quartz-carbonate tabular extension veins, with the development of swarms and nests of veins-veinlets, breccias and stockworks. Structures range from centimeter-wide individual veinlets to several meter-wide swarms of veins developed within broad mineralized structural corridors, with a metallic signature that consists of Au + Ag + Cu + Zn + Pb + As (± Te ± Bi ± Sb ± Hg ± W) assemblages. Veins are composed of multiple stages of mineralization, and the formation of these structures is enhanced by the presence of a local regime of extension and E-trending structures, including evidence of faults and shear zones with right-lateral displacement, which are likely involved in pluton emplacement and cooling. The ore mineralogy is composed of pyrrhotite, pyrite, chalcopyrite, sphalerite, galena and arsenopyrite assemblages formed in two or more mineralization stages, with complex Bi, Te, Sb and Hg mineral specimens associated with Au and Ag. Mineralized structures of the district present a preferential E-strike with dominant vertical to subvertical and occasional subhorizontal S-dips and secondary N- and NW-strikes that are steep to vertically E-dipping. \u0000The Frontino-Morrogacho Gold district presents characteristics related to the architecture, mineralogy and alteration of reduced (ilmenite-series) intrusion-related gold systems but is genetically associated with a parental oxidized magma source. The gold content is associated with three different families involving electrum, tellurides and alloys: gold rich (66 to 78% Au, 22 to 34% Ag), average (50 to 60% Au, 40 to 50% Ag) and silver rich (32 to 40% Au, 60 to 68% Ag). The formation of these bodies is associated with an N-S magmatic-metallogenic trend of Au-Ag-Cu deposits, which extend for more than 300 km along the Western Cordillera of Colombia. Similar plutonic suites span from the south of Chocó Province to the north of Antioquia Province, which indicates that the Frontino-Farallones-Botón arc can be proposed as an individual metallogenic belt.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114392515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-12DOI: 10.32685/0120-1425/BOL.GEOL.48.1.2021.503
Carolina Amaya López, Marion Weber Scharff, Mauricio Ibáñez Mejía, Federico Alberto Cuadros Jiménez, Jorge Julián Restrepo Álvarez, N. Botelho, Mario Maya Sánchez, Orlando Manuel Pérez Parra, Carlos Ramírez Cárdenas
The Neoproterozoic igneous rocks found in the municipality of San José del Guaviare include several isolated plutonic bodies that protrude from the Phanerozoic sedimentary cover in belts aligned NW-SE. Limited to the Guaviare department, these intrusions stretch from the La Lindosa mountain range to the corregimiento El Capricho. These plutonic bodies consist of nepheline syenites, nepheline monzosyenites, nepheline-bearing alkali-feldspar syenites, syenites, quartz-syenites, quartz-alkali-feldspar syenites, syenogranites, and quartz-rich granitoids, which have been grouped and termed the San José del Guaviare Syenite unit (SJGS). The intrusion of the unit occurred in the Ediacaran (604 ± 7 Ma and 620.5 ± 7.5 Ma) by mantle-derived alkaline magmas formed in anorogenic settings, most likely in rift-like stretching zones. The silica-subsaturated magma may have reacted with host rocks at the crust level, producing some silica-saturated igneous rocks, such as syenogranites and quartz-syenites, which are found in the El Capricho and Cerritos bodies.
在San jos del Guaviare市发现的新元古代火成岩包括几个孤立的深成岩体，它们从显生宙的沉积盖层中突出，呈北西-东南排列。这些入侵仅限于Guaviare省，从La Lindosa山脉延伸到El Capricho。这些深岩体由霞石正长岩、霞石二长长岩、含霞石碱长石正长岩、正长岩、石英正长岩、石英碱长石正长岩、正长花岗岩和富石英花岗岩组成，统称为San joss del Guaviare正长岩单元(SJGS)。该单元的侵入发生在埃迪卡拉纪(604±7 Ma和620.5±7.5 Ma)，主要是由在造山环境下形成的幔源碱性岩浆侵入，最有可能是在裂口状伸展带。硅质亚饱和岩浆可能在地壳水平上与主岩发生反应，产生了一些硅质饱和的火成岩，如正长花岗岩和石英正长岩，这些岩石在El Capricho和Cerritos中发现。
{"title":"San José de Guaviare Syenite, Colombia: Repeated Ediacaran intrusions in the northwestern Amazonian Craton","authors":"Carolina Amaya López, Marion Weber Scharff, Mauricio Ibáñez Mejía, Federico Alberto Cuadros Jiménez, Jorge Julián Restrepo Álvarez, N. Botelho, Mario Maya Sánchez, Orlando Manuel Pérez Parra, Carlos Ramírez Cárdenas","doi":"10.32685/0120-1425/BOL.GEOL.48.1.2021.503","DOIUrl":"https://doi.org/10.32685/0120-1425/BOL.GEOL.48.1.2021.503","url":null,"abstract":"The Neoproterozoic igneous rocks found in the municipality of San José del Guaviare include several isolated plutonic bodies that protrude from the Phanerozoic sedimentary cover in belts aligned NW-SE. Limited to the Guaviare department, these intrusions stretch from the La Lindosa mountain range to the corregimiento El Capricho. These plutonic bodies consist of nepheline syenites, nepheline monzosyenites, nepheline-bearing alkali-feldspar syenites, syenites, quartz-syenites, quartz-alkali-feldspar syenites, syenogranites, and quartz-rich granitoids, which have been grouped and termed the San José del Guaviare Syenite unit (SJGS). \u0000The intrusion of the unit occurred in the Ediacaran (604 ± 7 Ma and 620.5 ± 7.5 Ma) by mantle-derived alkaline magmas formed in anorogenic settings, most likely in rift-like stretching zones. The silica-subsaturated magma may have reacted with host rocks at the crust level, producing some silica-saturated igneous rocks, such as syenogranites and quartz-syenites, which are found in the El Capricho and Cerritos bodies.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125401681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-12DOI: 10.32685/0120-1425/BOL.GEOL.48.1.2021.529
E. Rossello, G. Veroslavsky, Jorge N. Santa Cruz
The proposal of the Quilmes Tectonic Trough (Fosa tectónica de Quilmes – FQ) as the extension of the southern end of the Santa Lucía basin in Uruguay and its connection to the Salado basin in Argentina suggest the existence of a large sedimentary volume capable of housing a new aquifer on the La Plata River coast. However, the sedimentary volumes that form the FQ are hidden under a thick, recently deposited cover, and thus, there is a lack of studies on the nature of this formation. Nevertheless, the Uruguayan section of the Meso-Cenozoic depocenter of the Santa Lucía basin has been more thoroughly studied for hydrocarbon exploration, which enabled us to estimate the equivalent tectosedimentary characteristics in the FQ. In the Uruguayan territory, three aquifer systems of the Santa Lucía basin are exploited: the Raigón (Plio-Pleistocene) aquifer, which is the most important source of groundwater for various uses in the south-central region of Uruguay, and the Mercedes (Upper Cretaceous) and Migues (Lower Cretaceous) aquifers, which are also used, albeit to a lesser extent, for drinking water, irrigation, and industrial purposes. The Migues aquifer, the least known of the three, shows a variable depth ranging from 100 to 1500 m and considerable stratigraphic sequences of porous and permeable sandstones. These sandstones provide the aquifer with very good qualities as a reservoir rock; as such, the Migues aquifer has been studied for its potential natural gas reserves and geothermal and water resources. Accordingly, if the same sequences with equivalent sedimentary and hydrogeological qualities are present in the FQ, similar aquifers with interesting properties may remain unidentified along the Buenos Aires coast beneath the intensely explored Puelches, Pampeano and Paraná aquifers. In conclusion, specific exploratory activities may prove the existence and quality of these hydrogeological resources, the regional slope toward the southwest from the Uruguayan outcrops, upwelling or semiupwelling conditions and even geothermal energy associated with the deepest cretaceous aquifers.
Quilmes构造槽(Fosa tectónica de Quilmes - FQ)是乌拉圭Santa Lucía盆地南端的延伸，它与阿根廷Salado盆地相连，这表明在拉普拉塔河沿岸存在一个能够容纳新含水层的大型沉积体。然而，形成FQ的沉积体隐藏在一个厚的，最近沉积的覆盖层之下，因此，缺乏对该地层性质的研究。尽管如此，Santa Lucía盆地中新生代沉积中心乌拉圭剖面的油气勘探研究更为深入，使我们能够估计FQ的等效构造沉积特征。在乌拉圭境内，Santa Lucía盆地的三个含水层系统被开发:Raigón(上新世-更新世)含水层，这是乌拉圭中南部地区各种用途的最重要的地下水来源;Mercedes(上白垩纪)和Migues(下白垩纪)含水层，也被用于饮用水、灌溉和工业用途，尽管程度较小。Migues含水层是三个含水层中最不为人所知的，其深度从100米到1500米不等，具有相当多的多孔性和渗透性砂岩层序。这些砂岩为含水层提供了很好的储层性质;因此，已对Migues含水层的潜在天然气储量以及地热和水资源进行了研究。因此，如果在FQ中存在具有相同沉积和水文地质质量的相同层序，那么在经过深入探索的Puelches, Pampeano和paran含水层下，沿着布宜诺斯艾利斯海岸可能仍未发现具有有趣性质的类似含水层。总之，具体的勘探活动可以证明这些水文地质资源的存在和质量，从乌拉圭露头向西南的区域斜坡，上升流或半上升流条件，甚至与最深的白垩纪含水层相关的地热能。
{"title":"Possible hydrogeological and thermal conditions of the Quilmes Tectonic Trough (Buenos Aires Province, Argentina): a working hypothesis","authors":"E. Rossello, G. Veroslavsky, Jorge N. Santa Cruz","doi":"10.32685/0120-1425/BOL.GEOL.48.1.2021.529","DOIUrl":"https://doi.org/10.32685/0120-1425/BOL.GEOL.48.1.2021.529","url":null,"abstract":"The proposal of the Quilmes Tectonic Trough (Fosa tectónica de Quilmes – FQ) as the extension of the southern end of the Santa Lucía basin in Uruguay and its connection to the Salado basin in Argentina suggest the existence of a large sedimentary volume capable of housing a new aquifer on the La Plata River coast. However, the sedimentary volumes that form the FQ are hidden under a thick, recently deposited cover, and thus, there is a lack of studies on the nature of this formation. Nevertheless, the Uruguayan section of the Meso-Cenozoic depocenter of the Santa Lucía basin has been more thoroughly studied for hydrocarbon exploration, which enabled us to estimate the equivalent tectosedimentary characteristics in the FQ. In the Uruguayan territory, three aquifer systems of the Santa Lucía basin are exploited: the Raigón (Plio-Pleistocene) aquifer, which is the most important source of groundwater for various uses in the south-central region of Uruguay, and the Mercedes (Upper Cretaceous) and Migues (Lower Cretaceous) aquifers, which are also used, albeit to a lesser extent, for drinking water, irrigation, and industrial purposes. The Migues aquifer, the least known of the three, shows a variable depth ranging from 100 to 1500 m and considerable stratigraphic sequences of porous and permeable sandstones. These sandstones provide the aquifer with very good qualities as a reservoir rock; as such, the Migues aquifer has been studied for its potential natural gas reserves and geothermal and water resources. Accordingly, if the same sequences with equivalent sedimentary and hydrogeological qualities are present in the FQ, similar aquifers with interesting properties may remain unidentified along the Buenos Aires coast beneath the intensely explored Puelches, Pampeano and Paraná aquifers. In conclusion, specific exploratory activities may prove the existence and quality of these hydrogeological resources, the regional slope toward the southwest from the Uruguayan outcrops, upwelling or semiupwelling conditions and even geothermal energy associated with the deepest cretaceous aquifers.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132214785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-12DOI: 10.32685/0120-1425/BOL.GEOL.48.1.2021.504
Julián Andrés López Isaza, Mario Andrés Cuéllar Cárdenas, Lina María Cetina Tarazona, Anny Julieth Forero Ortega, Ana Milena Suárez Arias, Oscar Freddy Muñoz Rodríguez, Luis Miguel Aguirre Hoyos, María Juliana Gutiérrez López
The description of the fabric elements represented by the linear and planar structures present at different scales is a key component of fieldwork. A scheme is proposed for the systematic registration of planes and lineations, coded as S (planar surfaces), F (folds), and L (lineations), among others, that allows for the orderly storage of the measurements taken. This scheme includes information related to the kinematics, the kinematic indicators, and the certainty or reliability ascribed to the assigned movement. In the fieldwork, the graphic representation of the structural measures in modified projection nets includes concentric circles for each dip. Direct drawing of the outcrop data is undertaken, dispensing with the use of tracing or transparent paper. The stereograms resulting from the graphic representation in the modified Wulff stereographic projection net, and the modified Schmidt equal-area net, can be complemented by rose diagrams for visualization of the spatial ordering. During field campaigns in the outcrops, it is essential to visualize the spatial orientation of the data in the diagrams to determine the main structural trends, the vergence, the kinematic nature of faults and shear zones, paleo-stress tensors, and to differentiate structural domains, among others. This information supports the reconstruction of geological and tectonic history and the establishment of relationships between the different geological processes.
{"title":"Graphical representation of structural data in the field: A methodological proposal for application in deformed areas","authors":"Julián Andrés López Isaza, Mario Andrés Cuéllar Cárdenas, Lina María Cetina Tarazona, Anny Julieth Forero Ortega, Ana Milena Suárez Arias, Oscar Freddy Muñoz Rodríguez, Luis Miguel Aguirre Hoyos, María Juliana Gutiérrez López","doi":"10.32685/0120-1425/BOL.GEOL.48.1.2021.504","DOIUrl":"https://doi.org/10.32685/0120-1425/BOL.GEOL.48.1.2021.504","url":null,"abstract":"The description of the fabric elements represented by the linear and planar structures present at different scales is a key component of fieldwork. A scheme is proposed for the systematic registration of planes and lineations, coded as S (planar surfaces), F (folds), and L (lineations), among others, that allows for the orderly storage of the measurements taken. This scheme includes information related to the kinematics, the kinematic indicators, and the certainty or reliability ascribed to the assigned movement. In the fieldwork, the graphic representation of the structural measures in modified projection nets includes concentric circles for each dip. Direct drawing of the outcrop data is undertaken, dispensing with the use of tracing or transparent paper. The stereograms resulting from the graphic representation in the modified Wulff stereographic projection net, and the modified Schmidt equal-area net, can be complemented by rose diagrams for visualization of the spatial ordering. During field campaigns in the outcrops, it is essential to visualize the spatial orientation of the data in the diagrams to determine the main structural trends, the vergence, the kinematic nature of faults and shear zones, paleo-stress tensors, and to differentiate structural domains, among others. This information supports the reconstruction of geological and tectonic history and the establishment of relationships between the different geological processes.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117059237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-15DOI: 10.32685/0120-1425/BOLETINGEO.45.2019.487
Milton David Lozada Molina, Frank David Lascarro Navarro, Luisa Fernanda León Díaz, Elías Ernesto Rojas Martínez, Fabio enrique Carrillo Bolaño, Luis Carlos Tapia Tavera, Dino Carmelo Manco Jaraba
In the department of Cesar, Municipality of Becerril, there are extensive outcroppings of Cretaceous rocks with calcareous sequences belonging to the Lagunitas and Aguas Blancas Formations, the Cogollo Group, and the La Luna Formation. This study presents the mapping of a 25 km2 are in the eastern sector of the Municipality of Becerril, intended to contribute geological knowledge of this area through field work, identification of geomorphological units and petrographic descriptions at a scale 1:25,000. The Lagunitas Formation is characterized by a succession of dark gray massive fossiliferous limestone intercalated with calcareous mudstone and lumachellic limestone. From the Aguas Blancas Formation, the Animas Member is identified in detail, consisting of calcareous mudstone with abundant organic matter interbedded with black micritic limestones that grades horizontally to sandstones with fine-grained calcareous cement. The Tucuy Member consists of calcareous siltstone, fine-grained sandstone and carbonated claystone. The Maracas Member consists mainly of massive lumachellic limestone. Similarly, four geomorphological environments were identified: structural, identifying units of hog-backs, homoclinal ridges and cuestas; denudation, identifying units such as erosion scarps, lightly bisected hills and undulating interfluves; karstic, with units of karstic valley and karstic slope; and fluvial, with the floodplain unit.
{"title":"Contribución al conocimiento geológico de la Serranía del Perijá mediante cartografía a escala 1:25.000 del Grupo Cogollo, en el sector oriental del municipio de Becerril, Cesar","authors":"Milton David Lozada Molina, Frank David Lascarro Navarro, Luisa Fernanda León Díaz, Elías Ernesto Rojas Martínez, Fabio enrique Carrillo Bolaño, Luis Carlos Tapia Tavera, Dino Carmelo Manco Jaraba","doi":"10.32685/0120-1425/BOLETINGEO.45.2019.487","DOIUrl":"https://doi.org/10.32685/0120-1425/BOLETINGEO.45.2019.487","url":null,"abstract":"In the department of Cesar, Municipality of Becerril, there are extensive outcroppings of Cretaceous rocks with calcareous sequences belonging to the Lagunitas and Aguas Blancas Formations, the Cogollo Group, and the La Luna Formation. This study presents the mapping of a 25 km2 are in the eastern sector of the Municipality of Becerril, intended to contribute geological knowledge of this area through field work, identification of geomorphological units and petrographic descriptions at a scale 1:25,000. The Lagunitas Formation is characterized by a succession of dark gray massive fossiliferous limestone intercalated with calcareous mudstone and lumachellic limestone. From the Aguas Blancas Formation, the Animas Member is identified in detail, consisting of calcareous mudstone with abundant organic matter interbedded with black micritic limestones that grades horizontally to sandstones with fine-grained calcareous cement. The Tucuy Member consists of calcareous siltstone, fine-grained sandstone and carbonated claystone. The Maracas Member consists mainly of massive lumachellic limestone. Similarly, four geomorphological environments were identified: structural, identifying units of hog-backs, homoclinal ridges and cuestas; denudation, identifying units such as erosion scarps, lightly bisected hills and undulating interfluves; karstic, with units of karstic valley and karstic slope; and fluvial, with the floodplain unit.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115636506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-15DOI: 10.32685/0120-1425/BOLETINGEO.45.2019.484
Jimmy Alejandro Muñoz Rocha, Alejandro Piraquive, José Alejandro Franco Victoria, Amed Bonilla Pérez, Luz Mary Peña Urueña, Thomas Heinrich Cramer, Lorena del Pilar Rayo Rocha, Nicolás Villamizar Escalante
With the aim of expanding the reference materials of the Geochronology Laboratory of the Colombian Geological Survey (LG-SGC, in Spanish), zircons were collected from the nepheline syenite of San Jose del Guaviare, Jordan locality (Colombia). The SNG-1 sample was composed of 24 zircons selected from the fraction between 2 and 5 millimeters long, which were mounted and polished in an epoxy resin block. The zircons were dated by analyzing the isotopic ratios of uranium and lead using the LA-ICPMS method. In the LG-SGC, 92 points on the zircons were selected for analysis, and at the University of Rennes in France (LG-URF), 24 points from crystals found nearby were selected for analysis from a previous cathodoluminescence study. Concordant ages for the zircons for both laboratories corresponded to a crystallization age of 608 ± 1.2 Ma and 602 ± 3 Ma, respectively, which differ by less than 1% despite the difference in instrumentation and analytical procedures. For systematic error correction and quality control, international reference material, such as Plesovice, GJ-1, FC-5 Duluth and Mount Dromedary zircon, was used. The uncertainties generated during the analyses are similar (1.2 and 3.2 Ma), and the mean square-weighted deviation (MSWD) of the concordia diagrams was < 1 in both cases, indicating low dispersion of the results. Some discordant ages show that the U/Pb ratios are not uniform, as expected for a primary reference material. However, we believe that the zircons of the Jordan syenite have potential use as a secondary reference material for the LG-SGC provided they are carefully selected and prepared, their geochemical content (including rare earth elements, REE) is characterized, and quality monitoring of U/Pb dating is performed, as these zircons are large, reaching up to 4 cm, abundant, and possible to collect in the Colombian territory.
为了扩充哥伦比亚地质调查局地质年代学实验室(西班牙语:LG-SGC)的参考资料，从哥伦比亚约旦地区San Jose del Guaviare的榴辉石正长岩中采集了锆石。SNG-1样品由24颗锆石组成，这些锆石从2至5毫米长的碎片中选择，并在环氧树脂块中进行安装和抛光。采用LA-ICPMS法分析铀、铅同位素比值，确定了锆石的年代。在LG-SGC中，锆石上的92个点被选中进行分析，而在法国雷恩大学(LG-URF)，从之前的阴极发光研究中，从附近发现的晶体中选择了24个点进行分析。两个实验室锆石的一致年龄分别对应于608±1.2 Ma和602±3 Ma的结晶年龄，尽管仪器和分析方法不同，但差异小于1%。采用Plesovice、GJ-1、FC-5 Duluth和Mount Dromedary锆石等国际标准物质进行系统误差校正和质量控制。分析过程中产生的不确定性相似(1.2和3.2 Ma)，两种情况下的concordia图的均方加权偏差(MSWD)均< 1，表明结果的分散性较低。一些不一致的年龄表明，U/Pb比率并不均匀，这是对初级参考物质的预期。然而，我们认为约旦正长岩的锆石有潜力作为LG-SGC的二级参考物质，只要对其进行精心挑选和制备，对其地球化学含量(包括稀土元素，REE)进行表征，并进行U/Pb测年的质量监测，因为这些锆石体积大，可达4厘米，储量丰富，并且在哥伦比亚境内有可能收集到。
{"title":"Megacircones ediacáricos de la sienita nefelínica de San José del Guaviare y su potencial como material de referencia para datación U/Pb mediante LA-ICP-MS","authors":"Jimmy Alejandro Muñoz Rocha, Alejandro Piraquive, José Alejandro Franco Victoria, Amed Bonilla Pérez, Luz Mary Peña Urueña, Thomas Heinrich Cramer, Lorena del Pilar Rayo Rocha, Nicolás Villamizar Escalante","doi":"10.32685/0120-1425/BOLETINGEO.45.2019.484","DOIUrl":"https://doi.org/10.32685/0120-1425/BOLETINGEO.45.2019.484","url":null,"abstract":"With the aim of expanding the reference materials of the Geochronology Laboratory of the Colombian Geological Survey (LG-SGC, in Spanish), zircons were collected from the nepheline syenite of San Jose del Guaviare, Jordan locality (Colombia). The SNG-1 sample was composed of 24 zircons selected from the fraction between 2 and 5 millimeters long, which were mounted and polished in an epoxy resin block. The zircons were dated by analyzing the isotopic ratios of uranium and lead using the LA-ICPMS method. In the LG-SGC, 92 points on the zircons were selected for analysis, and at the University of Rennes in France (LG-URF), 24 points from crystals found nearby were selected for analysis from a previous cathodoluminescence study. Concordant ages for the zircons for both laboratories corresponded to a crystallization age of 608 ± 1.2 Ma and 602 ± 3 Ma, respectively, which differ by less than 1% despite the difference in instrumentation and analytical procedures. For systematic error correction and quality control, international reference material, such as Plesovice, GJ-1, FC-5 Duluth and Mount Dromedary zircon, was used. The uncertainties generated during the analyses are similar (1.2 and 3.2 Ma), and the mean square-weighted deviation (MSWD) of the concordia diagrams was < 1 in both cases, indicating low dispersion of the results. Some discordant ages show that the U/Pb ratios are not uniform, as expected for a primary reference material. However, we believe that the zircons of the Jordan syenite have potential use as a secondary reference material for the LG-SGC provided they are carefully selected and prepared, their geochemical content (including rare earth elements, REE) is characterized, and quality monitoring of U/Pb dating is performed, as these zircons are large, reaching up to 4 cm, abundant, and possible to collect in the Colombian territory.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124423660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-15DOI: 10.32685/0120-1425/BOLETINGEO.45.2019.486
R. Melo
The geological explorations carried out by the Colombian Geological Survey (SGC, in Spanish) between 2005 and 2008 show that the potential areas for exploration and exploitation of emeralds in the Western Emerald Belt (CEOC, in Spanish) are closely related to the Muzo (Hauterivian-Barremian age) and Rosa Blanca (Valanginian age) geological formations, and in the Eastern Emerald Belt (CEOR, in Spanish), are associated to the Santa Rosa and Chivor formations (Berriasian age). Mineralization is associated with various mesoscopic tectonic structures with hydrothermal alteration.
{"title":"Notas sobre el contexto tectonoestratigráfico de formación de las esmeraldas colombianas","authors":"R. Melo","doi":"10.32685/0120-1425/BOLETINGEO.45.2019.486","DOIUrl":"https://doi.org/10.32685/0120-1425/BOLETINGEO.45.2019.486","url":null,"abstract":"The geological explorations carried out by the Colombian Geological Survey (SGC, in Spanish) between 2005 and 2008 show that the potential areas for exploration and exploitation of emeralds in the Western Emerald Belt (CEOC, in Spanish) are closely related to the Muzo (Hauterivian-Barremian age) and Rosa Blanca (Valanginian age) geological formations, and in the Eastern Emerald Belt (CEOR, in Spanish), are associated to the Santa Rosa and Chivor formations (Berriasian age). Mineralization is associated with various mesoscopic tectonic structures with hydrothermal alteration.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"282 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131744178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-15DOI: 10.32685/0120-1425/BOLETINGEO.45.2019.485
Manuel Guillermo Zafra Dulcey
This work presents the boundaries of a new area of interest for the detailed exploration of emeralds in Colombia, identified through the interpretation of geobotanical anomalies in areas of dense vegetation. A methodology was designed in which fifteen vegetation indices were calculated. The anomalies correlated most with the lineaments detected from the interpretation of a shaded-relief model generated from a digital terrain model (DTM) were selected. A detailed spectral analysis in the mineralized zones of the area with the highest correlation showed a halo of vegetative stress in all studied cases; moreover, the analysis corroborated a direct relationship between the albitization present in the mineralized zones, the lineaments and the degree of vegetative stress. A sector between the Coscuez mine and the La Pita mine was identified as a target for detailed exploration, where the vegetation indexes indicate less vegetative stress and correlate better with the natural terrain lineaments. It was found that the proposed methodology based on geobotanical anomalies yields consistent results and can be used as a tool for emerald exploration.
{"title":"Análisis de anomalías geobotánicas a partir del procesamiento e interpretación de productos de sensores remotos, estudio de caso: occidente de Boyacá (Colombia)","authors":"Manuel Guillermo Zafra Dulcey","doi":"10.32685/0120-1425/BOLETINGEO.45.2019.485","DOIUrl":"https://doi.org/10.32685/0120-1425/BOLETINGEO.45.2019.485","url":null,"abstract":"This work presents the boundaries of a new area of interest for the detailed exploration of emeralds in Colombia, identified through the interpretation of geobotanical anomalies in areas of dense vegetation. A methodology was designed in which fifteen vegetation indices were calculated. The anomalies correlated most with the lineaments detected from the interpretation of a shaded-relief model generated from a digital terrain model (DTM) were selected. A detailed spectral analysis in the mineralized zones of the area with the highest correlation showed a halo of vegetative stress in all studied cases; moreover, the analysis corroborated a direct relationship between the albitization present in the mineralized zones, the lineaments and the degree of vegetative stress. A sector between the Coscuez mine and the La Pita mine was identified as a target for detailed exploration, where the vegetation indexes indicate less vegetative stress and correlate better with the natural terrain lineaments. It was found that the proposed methodology based on geobotanical anomalies yields consistent results and can be used as a tool for emerald exploration.","PeriodicalId":124675,"journal":{"name":"Boletín Geológico","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121537262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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