Article
Geology
S. Leal, A. Lima, F. Noronha, J. Mortensen, D. MacKenzie
Summary: The Bigorne deposit is a orogenic gold system located in the northern Iberia, with gold-bearing veins cutting through synorogenic Variscan granites. The mineralization includes quartz-sulfide veins, disseminated sulfides, hydrothermal alteration, and oxidize fractures. The thermal evolution suggests that gold deposition occurred at lower temperatures. Isotope studies indicate that the gold-bearing fluid was generated from deep-crustal rocks during decompression triggered by crustal uplift.
ORE GEOLOGY REVIEWS
(2022)
Article
Geosciences, Multidisciplinary
Joana Alexandra Ferreira, Ines Pereira, Telmo Bento dos Santos, Joao Mata
Summary: The Figueira de Castelo Rodrigo-Lumbrales Anatectic Complex in the Central Iberian Zone has been studied for its metamorphic ages and exhumation history. The complex experienced peak metamorphism 316.8 +/- 2.0 million years ago, followed by rapid cooling and exhumation. The zircon ages of the complex are similar to those of the Excomungada Formation, suggesting a shared geological history. The detrital zircon ages of the Pinhao Formation indicate different sources from the Beiras Group, indicating the presence of a geological barrier. This study provides new insights into the geological evolution of the region.
JOURNAL OF THE GEOLOGICAL SOCIETY
(2022)
Article
Geochemistry & Geophysics
Gabriel Villasenor, Elizabeth J. Catlos, Igor Broska, Milan Kohut, Lubomir Hrasko, Kimberly Aguilera, Thomas M. Etzel, J. Richard Kyle, Daniel F. Stockli
Summary: The Gemeric and Veporic Superunits in the Western Carpathians are characterized by raremetal granites with ages traceable to Permian magmatism, indicating a regional connection to similar granite occurrences in Europe and the Western Mediterranean. These granites are thought to have originated from post-collisional extension processes involving significant decompression, crustal melting, and mantle lithosphere delamination that contributed to crustal thinning during the Variscan orogeny.
Article
Geosciences, Multidisciplinary
Francis Chopin, Remi Lepretre, Mohamed El Houicha, Anne-Sophie Tabaud, Karel Schulmann, Jitka Mikova, Jocelyn Barbarand, Ryma Chebli
Summary: This paper presents new U-Pb geochronological data on granitoids from the Moroccan Meseta Variscan belt. The results show a peak of magmatic activity at 335.2 +/- 0.8 Ma in the Western Meseta and early Visean magmatic activity in the Eastern Meseta. The study also suggests a possible relationship between the magmatic activity and the tectonic events in Northwest Africa. Evaluation: 8 points.
Article
Geology
Luc de Hoym de Marien, Pavel Pitra, Marc Poujol, Nathan Cogne, Florence Cagnard, Benjamin Le Bayon
Summary: Two eclogites from the French Massif Central underwent prograde evolution, heating, partial melting, and subsequent exhumation, revealing a complex tectonic history involving an Ordovician rifting event, Devonian subduction, and Carboniferous exhumation. The previously proposed Silurian age for the subduction has been definitively rejected. The petrochronological record of zircon shows a complex pattern of metamorphic ages, while apatite and rutile yield a well-defined age of about 350 Ma. Fractures filled with analcite, thomsonite, plagioclase, and biotite indicate late interaction with alkaline fluids at relatively low temperatures.
JOURNAL OF METAMORPHIC GEOLOGY
(2023)
Article
Geochemistry & Geophysics
Anthony I. S. Kemp, Jeffrey D. Vervoort, Andreas Petersson, R. Hugh Smithies, Yongjun Lu
Summary: This study analyzes samples from the Pilbara Craton in Western Australia and finds a connection between mantle and crustal processes throughout the craton's history. The evolution of the craton was mainly driven by the transformation of juvenile mantle materials into felsic igneous rocks, indicating sustained continental growth over the past 4 billion years. The collision of the East and West Pilbara terranes at 3.1 billion years ago increased the involvement of older crust in magma generation. This study highlights the importance of comparing mantle and crustal isotope records to understand crustal growth rates in ancient terranes.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Geosciences, Multidisciplinary
Tod Waight, Michael B. W. Fyhn, Tonny B. Thomsen, Tran Van Tri, Lars H. Nielsen, Ioannis Abatzis, Dirk Frei
Summary: Zircon ages and geochemistry of igneous rocks from SW Vietnam and S Cambodia reveal four main age groupings. The rocks show differences in geological structures and stratigraphy, possibly related to Pacific Plate subduction.
JOURNAL OF ASIAN EARTH SCIENCES
(2021)
Article
Geosciences, Multidisciplinary
A. Kaessner, M. Tichomirowa, M. Lapp, D. Leonhardt, M. Whitehouse, A. Gerdes
Summary: The study focuses on Late Paleozoic magmatism in the Lusatian Block of Central Europe, examining the spatial relationship of Variscan igneous rocks with major fault zones in the region. The research identifies two distinct magmatic episodes in the Lusatian Block, supported by new age and geochemical data, and suggests a post-collisional faulting interpretation for these events. The findings also challenge previous assumptions about the protolith of the Koenigshain pluton, pointing to acid or intermediate igneous rocks as the main source for the granitoids.
INTERNATIONAL JOURNAL OF EARTH SCIENCES
(2021)
Article
Geochemistry & Geophysics
M. Liesa, C. Aguilar, A. Castro, G. Gisbert, J. Reche, J. A. Munoz, M. Vila
Summary: The lower structural levels of the Variscan orogen in the Eastern Pyrenees exhibit three genetically associated magmatic suites, formed during the Late Carboniferous to Early Permian in a syn- to post-collisional setting. Geochemical comparisons with neighboring massifs suggest variable degrees of lower crustal assimilation in the granitoids and mafic complexes. Petrogenetic relationships and magma formation processes are inferred based on isotopic compositions and petrographic analysis.
Article
Geochemistry & Geophysics
Oscar Laurent, Simon Couzinie, Luc S. Doucet
Summary: The study reveals the timescales of lower crustal ultra-high temperature metamorphism and the production and transfer of granitic magmas. Zircon petrochronology of felsic and mafic granulite xenoliths from the Variscan eastern French Massif Central shows that these rocks underwent Variscan UHT peak metamorphism at 940-970°C and 8±2 kbar. The zircon U-Pb dates of the felsic granulites range from -315 to -265 Ma, indicating continuous crystallization of zircon upon cooling from the thermal peak. The emplacement of upper crustal granite started at 340 Ma and peaked at 313±3 Ma, reflecting melt extraction along the prograde path of the lower crust. The crystallization ages of mid-crustal migmatites (315-300 Ma) and lower crustal granulites (315-265 Ma) suggest slow cooling in the presence of melt.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Geochemistry & Geophysics
Martin Guitreau, Abdelmouhcine Gannoun, Zhengbin Deng, Marc Chaussidon, Frederic Moynier, Bernard Barbarin, Johanna Marin-Carbonne
Summary: This study investigates the silicon isotope signatures of zircon in various granite types to understand their fractionation behavior, which can be useful in studying magma evolution and identifying granite source areas. Silicon isotope ratios in zircon can track changes in magma temperature and composition, revealing complex processes like magma mingling, fractional crystallization, and multiple sources. The study highlights that silicon isotopes in zircon can complement existing techniques in granite studies and should not be used in isolation.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Geosciences, Multidisciplinary
Stephen Collett, Karel Schulmann, Pierig Deiller, Pavla Stipska, Vit Peresty, Marc Ulrich, Yingde Jiang, Luc de Hoym de Marien, Jitka Mikova
Summary: This article investigates the high-pressure and high-temperature metamorphism during the Mid-Devonian period in the Variscan Orogeny, focusing on the geological characteristics of the Marianske Lazne Complex (MLC). The unique position of MLC at the base of its original upper plate is highlighted. The study reveals that both MLC and the upper plate developed above a relatively unaltered Neoproterozoic lithospheric mantle, which is important for reconstructing the original architecture of the Variscan terranes.
GEOSCIENCE FRONTIERS
(2022)
Article
Geochemistry & Geophysics
Zi-Hao Wen, Lin Li, Daniel E. Harlov, Sheng-Rong Li
Summary: The Hewan granite porphyry is a newly discovered highly evolved gold deposit in northern China, consisting of two types of magmatic zircon - Type I and Type II. Type I zircon is enriched in certain elements while Type II zircon is relatively depleted. Geochemical analysis suggests that the Hewan granite porphyry was primarily derived from the melting of surrounding older rock. Type I zircons formed during this melting event and were later replaced by Type II zircon due to infiltration of a later fluid. The deposition of elemental gold in this shallow magma was facilitated by the presence of certain fluids and conditions.
Article
Geosciences, Multidisciplinary
A. S. Tabaud, P. Stipska, S. Mazur, K. Schulmann, J. Mikova, J. Wong, M. Sun
Summary: The study of rocks samples from GSM in Poland, using geochemistry and isotopic data, revealed the origin and geological evolution of sedimentary rocks in the area, suggesting that it may have been located along the northern periphery of the Gondwana margin, forming in the middle to late Cambrian period.
Article
Geosciences, Multidisciplinary
Jun Zhi, Ruxiong Lei, Boyang Chen, M. N. Muhtar, Zhijie Feng, Kai Zhang, Yuanfeng Cai, Changzhi Wu
Summary: The Zhangbaoshan super-large Rubidium deposit is a typical granite-type deposit located in the Eastern Tianshan. Different types of zircons from the highly evolved granite pluton suggest a transition from magmatic to F-rich hydrothermal stages, with mineralization likely occurring shortly after emplacement in the Early Triassic. The Triassic period is highlighted as a significant time for granitic magmatism and rare metal metallogeny in the Eastern Tianshan.
FRONTIERS IN EARTH SCIENCE
(2021)
Article
Geology
H. C. B. Martins, J. Abreu
ESTUDIOS GEOLOGICOS-MADRID
(2014)
Article
Geology
C. Cruz, M. A. Ribeiro, H. St'Ovaia, H. C. B. Martins
ESTUDIOS GEOLOGICOS-MADRID
(2014)
Article
Geology
J. A. Ferreira, M. A. Ribeiro, H. C. B. Martins
ESTUDIOS GEOLOGICOS-MADRID
(2014)
Article
Geosciences, Multidisciplinary
H. Sant'Ovaia, P. Nogueira, J. Carrilho Lopes, C. Gomes, M. A. Ribeiro, H. C. B. Martins, A. Doria, C. Cruz, L. Lopes, R. Sardinha, A. Rocha, F. Noronha
GEOLOGICAL MAGAZINE
(2015)
Article
Geochemistry & Geophysics
Helena C. B. Martins, Helena Sant'Ovaia, Fernando Noronha
Article
Geology
Antonio Joao Teixeira Oliveira, Helena Cristina Brites Martins, Helena Maria Sant'Ovaia Mendes da Silva
Summary: The study from the Lamas de Olo region in northern Portugal reveals the formation of microgranite and lamprophyre during the final stages of the Variscan orogeny, possibly influenced by regional geological structures. The microgranite likely originated from an evolved crustal source, while the lamprophyre may have been formed through low-degree melting of an enriched lithospheric mantle source.
JOURNAL OF IBERIAN GEOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Ana Goncalves, Helena Sant'Ovaia, Helena Cristina Brites Martins, Fernando Noronha
Summary: The Valpacos and Freixo de Numao granites in Northeastern Portugal were studied to understand the ascent and emplacement mechanisms and deformation patterns evolution. The magnetic fabrics of ValG were influenced by a combination of magmatic and tectonic fabrics, while FNG inherited a magmatic fabric from passive ascent and emplacement. Brittle structures recorded in both granites help reconstruct the rotation of maximum compressive stress.
INTERNATIONAL JOURNAL OF EARTH SCIENCES
(2022)
Article
Geochemistry & Geophysics
Helena Sant'Ovaia, Claudia Cruz, Alexandra Guedes, Helena Ribeiro, Patricia Santos, Sonia Pereira, Jorge Espinha Marques, Maria dos Anjos Ribeiro, Catarina Mansilha, Helena Cristina Brites Martins, Bruno Valentim, Joana Torres, Ilda Abreu, Fernando Noronha, Deolinda Flores
Summary: The study focused on the tungsten Regoufe mine, which stopped operations in the 1970s. The research evaluated the contamination of soil, plants, and water in the mining area, specifically looking at potentially toxic elements (PTEs). The results showed that the area had a high level of contamination, posing ecological risks, particularly due to contributions from arsenic (As) and cadmium (Cd). However, it was difficult to establish a direct link between As contamination and mining activities, as the soils were already enriched in metals and metalloids from natural geological processes. The study also found that PTE levels in plants were lower than in soil, but bioaccumulation was influenced by site-specific soil concentrations of As and Pb. Magnetic studies indicated the presence of technogenic particles, likely formed during ore processing/mining activities. Overall, the levels of PTEs in surface and groundwater samples were relatively low, with the exception of As, which exceeded drinking water standards.
Article
Geosciences, Multidisciplinary
Antonio Joao Teixeira Oliveira, Helena Cristina Brites Martins, Helena Maria Sant'Ovaia Mendes da Silva
Summary: Three large granite porphyries in northern Portugal were studied to enhance understanding of the regional felsic vein magmatism. These porphyries share similar mineralogical compositions and textures, emplaced along fractures during the Variscan orogeny, and affected by fast cooling, volatile loss, and hydrothermal alteration.
COMPTES RENDUS GEOSCIENCE
(2021)
Proceedings Paper
Geosciences, Multidisciplinary
Maria Anjos Ribeiro, Helena Martins, Helena Sant'Ovaia, Armanda Doria
16TH INTERNATIONAL MULTIDISCIPLINARY SCIENTIFIC GEOCONFERENCE, SGEM 2016: SCIENCE AND TECHNOLOGIES IN GEOLOGY, EXPLORATION AND MINING, VOL I
(2016)
Proceedings Paper
Engineering, Civil
Isabel Fernandes, Maria dos Anjos Ribeiro, Helena Martins, Maarten Broekmans, Ian Sims, Philip Nixon, Fernando Noronha
ENGINEERING GEOLOGY FOR SOCIETY AND TERRITORY, VOL 5: URBAN GEOLOGY, SUSTAINABLE PLANNING AND LANDSCAPE EXPLOITATION
(2015)