Cuba Abstracts

The Third International Ophiolite Wo
Source:    Publish Time: 2017-04-29 09:56   2344 Views   Size:  16px  14px  12px

The Third International Ophiolite Workshop of IGCP-649 Project successfully held in Cuba

During April 3rd-14th, the Third International Ophiolite Workshop of International Geoscience Programme “Diamonds and Recycled Mantle” (IGCP-649) was successfully held in Havana, Cuba. After the workshop, participants took part in the field trip of the Mayarí-Baracoa ophiolites and related chromitites in eastern Cuba. This Third International Ophiolite Workshop is jointly organized by the IGCP-649 Project Team and the Cuban Geological Survey. This workshop is one special session of the VII Cuba Earth Science Convention. Since 1980s, diamond, moissanite and other unusual minerals were successively reported to be recovered from peridotites and chromitites in ophiolites of different ages and locations. Under this background, the goal of the International Ophiolite workshop is to investigate the composition and evolution of deep mantle in the oceanic lithosphere by comparing study of ophiolites in different orogenic belts all over the world, and also to provide new ideas for chromitite prospecting and exploration by studying the deep-mantle origin of ophiolite and chromitite.

About 100 scientists from China, America, Germany, Canada, Russia, Turkey, Egypt, Cuba and countries around Cuba attended this ophiolite workshop of IGCP-649. After the workshop, 40 scientists participated in the field trip about the eastern Cuban ophiolites. At the beginning of the workshop, Dr. Enrique Castellanos Abella (Director of Cuba Ministry of Energy and Mines), Dr. Kenya E. Núñez Cambra (President of Cuba Geological Society), and Dr. Angelica Isabel Lianes Castro (Cuba Geological Survey) made the opening speeches. Angelica Isabel Lianes Castro and other members from Cuba Geological Survey organized the field investigation and introduction.

During the workshop, scientists from different countries reported the research status and progress on ophiolites of different tectonic settings in different locations of the world and also discussed the problems existing in the study of ophiolites and chromitites. Manuel Iturralde Vinent from Cuba Geological Survey systematically introduced the geological evolution of Cuba and the Cuban ophiolites, from which Chinese geologists who came to Cuba for the first time had benefited a lot. Dr. Jingsui Yang from Chinese Academy of Geological Sciences (CAGS) reported the progress on the studies of diamond and other unusual minerals recovered from different ophiolites and proposed a new name of “Luobusa-type” diamond for the diamond recovered from ophiolite. The new name of “Luobusa-type” diamond is named after the Luobusa ophiolite, from which the first “Luobusa-type” diamond was recovered. Michael Wiedenbeck from German Research Center for Geosciences (GFZ) introduced the advanced analytical technology which can be used in the study of ophiolites and chromitites. This workshop provided a precious opportunity for researchers working on ophiolites and chromitites to study and communicate with each other.

Cuba situated in Central America has experienced a complicated geological process including the generation and metamorphism of oceanic crust, the growth of island arc and the final emplacement of oceanic lithospheric relicts. Three major ophiolite-bearing units exists in Cuba including: 1) the northern ophiolitic belt; 2) the metamorphic basement of the Cretaceous volcanic arc terrane; and 3) tectonic slices in the Escambray massif (one of the metamorphic terranes) in Central Cuba. However, over 90% of the oceanic lithosphere remains in Cuba are included in the Northern ophiolitic belt (NOB). The NOB is mainly a large mélange that stretches 1000 km along the northern Cuba, whose blocks are composed mainly by ophiolitic suite components, floating in a serpentinitic matrix. The age of this ophiolitic belt is thought to be Upper Jurassic-Lower Cretaceous. Tectonized ultramafic rocks and cumulative rocks ate the most common lithologies, whereas the basalts and sedimentary rocks are poorly exposed. Only few age data are available for the NOB rocks.

Mayarí-Baracoa ophiolite in the eastern segment of the northern ophiolitic belt is the main chromitite mining area in Cuba. Mayarí-Baracoa ophiolite is mianly composed the Moa-Baracoa massif in the east and the Mayarí-Cristal massif in the west. The Moa-Baracoa massif covers an area of 1500 km2. This ophiolitic massif mainly composed of mantle peridotites and the Moho-transition zone rocks. Mayarí-Cristal massif is the most important high-Al chromitite mining area in Cuba, which has around 100 ore bodies. Of these ore bodies, Mercedita chromitite is the biggest one, having over 5 million tons of chromitite. The Mayarí-Cristal massif is about 1200 km2. This massif is dominated by mantle peridotites with the thickness of 5 km. Mayarí-Cristal mainly have two big high-Cr chromitite ore bodies with ore reserves of over 200 thousand tons. Both high-Cr and high-Al chromitites occur in the Havana-Matanza ophiolite of western Cuba, while only high-Cr chromitite occurs in Tibet, China. Metamorphic rocks including eclogite, amphibolite and antigoritite can be found in Cuban ophiolitic belt, which may have recorded the metamorphic history of Cuban ophiolites. During the field trip, peridotite, chromitite, mafic dike, cumulate gabbro, pegmatite and pillow lava in Mayarí-Baracoa ophiolites in eastern Cuba are investigated in detail. Mafic dike rocks in these ophiolites were sampled systematically for geochemical studies and age dating. Large amounts of peridotites and chromitites samples from Mayarí-Baracoa ophiolitic belts were collected for future mineral separation work and geochemical studies.

IGCP-649 is a global research programme, which is undertaken by Center for Advanced Research on Mantle (CARMA) of Institute of Geology, CAGs. This project will conduct extensive and systematic researches on peridotites, chromitites and related unusual minerals (diamond, moissanites and other unusual minerals) from different ophiolites in global orogenic belts, to discuss and understand new scientific problems such as the formation and origin of deep-mantle minerals in oceanic lithosphere, the origin of carbon source for “Luobusa-type” diamond, the evolution of earth mantle and the dynamic process of ophiolite emplacement. IGCP-649 project lasting for five years (2015-2020) were awarded and sponsored by UNESCO and IUGS. In August of 2015, the First Ophiolite Workshop was held in Xining of Qinghai Province, China. After the workshop, participants were organized to investigate the Early Paleozoic ophiolite and high-pressure metamorphic belt in Qilian Mountain. The Second Ophiolite Workshop was held in Cyprus. Field trip was organized to investigate the world-renowned Troodos ophiolite.

Simplified geological map of Cuba

Kenya E. Núñez Cambra, President of Cuba Geological Society, making the opening speech

Famous geologist Dr. Manuel Iturralde Vinent from Cuba Geological Survey making introduction of Cuba Geology

Participants listening to Michael Wiedenbeck’s report

Participants making discussion on posters

Cumulate gabbro in Cuba ophiolite

Massive chromitite hosted by harzburgite in Cuba ophiolite

Chromitite with typical nodular texture

Group photo of participants for the Third International Workshop of IGCP-649