scholarly journals Geochemical Signature and Magnetic Fabric of Capinha Massif (Fundão, Central Portugal): Genesis, Emplacement and Relation with W–Sn Mineralizations

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 557
Author(s):  
Ana Gonçalves ◽  
Helena Sant’Ovaia ◽  
Fernando Noronha
Keyword(s):  
Multidisciplinary Approach ◽  
Field Work ◽  
Magnetic Fabric ◽  
Brittle Deformation ◽  
Deformation Stages ◽  
Central Portugal ◽  
Variscan Granites ◽  
Serra Da Estrela ◽  
Host Rocks ◽  
Metasedimentary Sequence

The Fundão–Serra da Estrela–Capinha (FSEC) region is characterized by peraluminous to metaluminous Variscan granites intrusive in a complex and thick metasedimentary sequence. This work seeks to characterize the Capinha granite (CG), understand its spatial and genetic relationship with the host Peroviseu–Seia (PS), Belmonte–Covilhã (BC) and Fáguas granites, and evaluate its metallogenic potential. To achieve these goals, a multidisciplinary approach was undertaken, including field work and identification of the petrography and microstructures, whole rock geochemistry and anisotropy of magnetic susceptibility. Four distinct and independent differentiation trends were identified in the granites, namely, PS, BC, Fráguas and CG. The PS and BC played a role as host rocks for the W and Sn mineralizations. The Fráguas granite is anomalous in Sn and spatially related to the Sn–Li mineralizations, while the CG is anomalous in W and spatially related to W–Sn mineralizations. The post-tectonic CG is a peraluminous ilmenite-type whose ascent and emplacement were tectonically controlled. The Capinha magma used the intersection between the 25° N and 155° N strike–slip crustal scale faults for passive ascent and emplacement during the late-Variscan extensional phases. The magnetic fabric was drawn using an asymmetric tongue-shaped laccolith for CG. CG experienced two brittle deformation stages that marked the maximum compressive rotation from NE–SW to NNW–SSE.

Magmatic structures and kinematics emplacement of the Variscan granites from Central Portugal (Serra da Estrela and Castro Daire areas)

2010 ◽  
Vol 32 (10) ◽  
pp. 1450-1465 ◽  
Author(s):  
Helena Sant’Ovaia ◽  
Philippe Olivier ◽  
Narciso Ferreira ◽  
Fernando Noronha ◽  
Denis Leblanc
Keyword(s):  
Central Portugal ◽  
Variscan Granites ◽  
Serra Da Estrela

Defining the dynamics of groundwater in Serra da Estrela Mountain area, central Portugal: an isotopic and hydrogeochemical approach

2010 ◽  
Vol 19 (1) ◽  
pp. 117-131 ◽  
Author(s):  
Paula M. Carreira ◽  
José M. Marques ◽  
Jorge Espinha Marques ◽  
Helder I. Chaminé ◽  
Paulo E. Fonseca ◽  
...  
Keyword(s):  
Mountain Area ◽  
Central Portugal ◽  
Serra Da Estrela

Geoethical implications of water pollution by road de‐icing: lessons and way forward in a mountain protected area (Serra da Estrela, Central Portugal)

2021 ◽  
Author(s):  
Jorge Espinha Marques ◽  
Sara C. Antunes ◽  
João Honrado ◽  
Cláudia Carvalho-Santos ◽  
Paula M. Carreira ◽  
...  
Keyword(s):  
Water Pollution ◽  
Protected Area ◽  
Central Portugal ◽  
Serra Da Estrela

scholarly journals Field work in the north of the Ivisârtoq region, inner Godthåbsfjord, southern West Greenland

1983 ◽  
Vol 115 ◽  
pp. 49-56
Author(s):  
B Chadwick ◽  
M.A Crewe ◽  
J.F.W Park
Keyword(s):  
Field Work ◽  
Geological Survey ◽  
West Greenland ◽  
North West ◽  
The North ◽  
Field Investigations ◽  
New Findings ◽  
Host Rocks

The programme of field investigations in the north of the Ivisartoq region begun in 1981 by Chadwick & Crewe (1982) was continued in 1982. Julia Park began mapping the Taserssuaq granodiorite, its host rocks and the Ataneq fault in the north-west. Dur team was joined by D. Bellur, Geological Survey of India, nominally as an assistant. In this report we present only summary notes of new findings relevant to the interpretation of the geometry and chronology of this segment of the Archaean crust in southern West Greenland. We use the established terminology for the Archaean rocks of the Godthåbsfjord region.

Minor- and trace-element composition of trioctahedral micas: a review

2001 ◽  
Vol 65 (2) ◽  
pp. 249-276 ◽  
Author(s):  
G. Tischendorf ◽  
H.-J. Förster ◽  
B. Gottesmann
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Analytical Data ◽  
Distribution Patterns ◽  
Trace Element Composition ◽  
Element Composition ◽  
Element Partitioning ◽  
Analytical Strategies ◽  
Variscan Granites ◽  
Host Rocks

AbstractMore than 19,000 analytical data mainly from the literature were used to study statistically the distribution patterns of F and the oxides of minor and trace elements (Ti, Sn, Sc, V, Cr, Ga, Mn, Co, Ni, Zn, Sr, Ba, Rb, Cs) in trioctahedral micas of the system phlogopite-annite/siderophyllite-polylithionite (PASP), which is divided here into seven varieties, whose compositional ranges are defined by the parametermgli(= octahedral Mg minus Li). Plots of trace-element contentsvs.mglireveal that the elements form distinct groups according to the configuration of their distribution patterns. Substitution of most of these elements was established as a function ofmgli. Micas incorporate the elements in different abundances of up to four orders of magnitude between the concentration highs and lows in micas of ‘normal’ composition. Only Zn, Sr and Sc are poorly correlated tomgli. In compositional extremes, some elements (Zn, Mn, Ba, Sr, Cs, Rb) may be enriched by up to 2–3 orders of magnitude relative to their mean abundance in the respective mica variety. Mica/melt partition coefficients calculated for Variscan granites of the German Erzgebirge demonstrate that trace-element partitioning is strongly dependent on the position of the mica in the PASP system, which has to be considered in petrogenetic modelling.This review indicates that for a number of trace elements, the concentration ranges are poorly known for some of the mica varieties, as they are for particular host rocks (i.e. igneous rocks of A-type affiliation). The study should help to develop optimal analytical strategies and to provide a tool to distinguish between micas of ‘normal’ and ‘abnormal’ trace-element composition.

scholarly journals Mineral Exploration in Mawat Region, Kurdistan-Iraq, Based on Satellite Data and Terrain Prospection

2021 ◽  
Vol 8 (4) ◽  
pp. 249-272
Author(s):  
Marinko Oluić ◽  
Sreten Romandić ◽  
Ratko Vasiljević
Keyword(s):  
Satellite Data ◽  
Mineral Exploration ◽  
Digital Processing ◽  
Field Work ◽  
Measured Concentration ◽  
Copper Mineralization ◽  
Rock Formations ◽  
Lithological Composition ◽  
Color Composite ◽  
Host Rocks

The main goal of the presented exploration was to estimate potential for mineralization in the Mawat ophiolitic massif in Kurdistan, Iraq. The aim of the study was to explore existing copper mineralization and assessor elements gold, platinoids and chromium. Geological exploration detected two types of Cu occurrence a) secondary Cu carbonates (malachite) and b) Cu sulfides (chalcopyrite-pyrite). The Mawat region is mostly built of ultrabasic and basic rocks: peridotites, gabbros, serpentinites and basalts which are heavily deformed, with faults mostly oriented NNW-SSE, and NE-SW. The first phase of exploration comprised digital processing of ASTER and QuickBird satellite images, with appropriate geometrical and radiometric corrections and transformation into coordinate system. Color composite images were produced in different scales. They served to define lithological composition, tectonic settings, location of the points of interest etc. The field work was designed to check satellite data in situ, with focus on perspective rock formations, which might host copper mineralization, and other elements. The host rocks of the ore occurrences are primarily gabbros and metagabbros intersected by diabase dykes, epidote and quartz veins. Secondary mineralization is the product of surficial weathering and it is represented by malachite and limonite. The geophysical survey was very useful in the detection of area with elevated induced polarization and low resistivity. Three perspective areas have been selected for detailed explorations: Waraz, Mirava-Chenara and Konjirin-Kuradawi. The concentration of copper varies highly in very wide ranges; the maximum measured concentration of Cu was determined in Waraz area 6.7%. Some rock samples also show concentration of gold from 0.36 to 2.59 ppm Au. Keywords: Mawat ophiolitic massif, geologic-geophysical explorations, copper mineralization, Kurdistan-Iraq

Magnetic fabrics in Portuguese Variscan granites: structural markers of the Variscan orogeny

2020 ◽  
Author(s):  
Helena Sant Ovaia ◽  
Ana Gonçalves ◽  
Claudia Cruz ◽  
Fernando Noronha
Keyword(s):  
Stress Field ◽  
Shear Zones ◽  
Ductile Deformation ◽  
Magnetic Fabric ◽  
Variscan Orogeny ◽  
Maximum Compression ◽  
Compression Direction ◽  
Magnetic Fabrics ◽  
Central Portugal ◽  
Magnetic Lineations

<p>This work focuses on the magnetic fabric of 20 variscan granitic massifs from northern and central Portugal and considers the Anisotropy of Magnetic Susceptibility (AMS) results obtained in about 750 sampling sites. In the northern and central Portugal, three main ductile deformation phases were recognized and described: D<sub>1</sub>, D<sub>2</sub> and D<sub>3</sub>, being the variscan magmatism events mainly related to D<sub>3</sub> phase. D<sub>3</sub> produced wide amplitude folds with NW-SE subhorizontal axial plane and subvertical dextral and sinistral ductile shear zones, forming obtuse angles with the maximum compression direction, σ1, NE-SW oriented. The post-D<sub>3</sub> brittle phase was responsible for the development of conjugate faults (NNW-SSE, NNE-SSW and ENE-WSW), related to a N-S maximum compression. The studied granites were subdivided according to U-Pb dating, field observations and considering the chronology of their emplacement relative to the D<sub>3</sub> phase of Variscan orogeny. Therefore, the studied granites are subdivided into: (1) syn-D<sub>3</sub> two-mica granites, ca. 311 Ma; (2) late-D<sub>3</sub> monzogranites, biotite-rich and two-mica granites, ca. 300 Ma; (3) post-D<sub>3</sub> monzogranites and biotite-rich granites, ca. 299 – 297 Ma. Magnetic fabric gives two types of directional data, magnetic foliations and magnetic lineations, which provide important information regarding the orientation of the magmatic flow, feeder zone location, relationship between the magma emplacement and tectonics and, also, the stress field. The data obtained for the magnetic fabric, based on AMS technique, allowed concluding: (i) syn-D<sub>3</sub> granites show magnetic foliations and lineations consistent with the syn-D<sub>3</sub> variscan structures ca. N110°-120°E, related to a NE-SW maximum stress field . The foliations are, mainly, subvertical (> 60º), which may indicate a high thickness of the granitic body and deep rooting; on the other hand, the magnetic lineations exhibit variables plunges. (ii) Late-D<sub>3</sub> granites are characterized by foliations and lineations, dominantly NNW-SSE to NNE-SSW oriented. The foliations are subvertical dips (> 60º) and the lineations have, generally, soft plunges. (iii) Post-D<sub>3</sub> granites have, in general, magnetic foliations and lineations associated with important regional post-D<sub>3</sub> brittle structures, which display NNE-SSW and ENE-WSW trending. The subhorizontal fabric may suggest a small thickness of the granitic bodies. In all granite sets under study there is a dominance of weakly dipping lineations (slope <60º), indicating that the feeding zones are deep, which supports the idea of an emplacement at high structural levels.</p><p>Acknowledgments: The authors thank Department of Geosciences, Environment and Spatial Planning at Faculty of Sciences of the University of Porto and the Earth Sciences Institute (Porto Pole, Project COMPETE 2020 (UID/GEO/04683/2013), reference POCI-01-0145-FEDER-007690).</p>

New paleomagnetic data for Ochotsk-Chukotka volcanic belt

2020 ◽  
Author(s):  
Ivan Lebedev ◽  
Olesya Usanova ◽  
Tanya Fadeeva ◽  
Florian Lhuillier ◽  
Baha Eid ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Field Work ◽  
Magnetic Fabric ◽  
Time Interval ◽  
The North ◽  
Secular Variations ◽  
North Eastern ◽  
Chukotka Volcanic Belt ◽  
Normal Polarity

<p class="db9fe9049761426654245bb2dd862eecMsoNormal"><span lang="EN-US">The Okhotsk-Chukotka volcanic belt (OChVB),  located in the north-eastern part of Russia, is a unique volcanic structure, which has been formed over a wide time interval from Aptian (K1) to Cenomanian (K2) [Tihomirov, 2018]. Age of its formation nearly coincides with the occurrence of the Cretaceous geomagnetic superchron of normal polarity. Thus, the volcanic formations of the OChVB represent a promising object to study the characteristics of the geomagnetic field during the Cretaceous superchron (direction, paleointensity, secular variations) needed to test various models explaining superchrons’s existence .</span></p> <p class="db9fe9049761426654245bb2dd862eecMsoNormal"><span lang="EN-US">During the reconnaissance field work of the summer 2019 we have sampled volcanic rocks in 9 sections each includes from 8 to 30 sites corresponding either to lava flow or to tuff layers.</span></p> <p class="db9fe9049761426654245bb2dd862eecMsoNormal"><span lang="EN-US">Up to date we have carried out AF demagnetization, petromagnetic and AMS studies. Demagnetisations studies demonstrate that the rocks contain paleomagnetic record of the ancient (primary?) magnetization of good to excellent quality. Petromagnetic experiments indicate that the main magnetic mineral in majority of studied volcanics is titanomagnetite with pseudo-single domain grain size. We use the magnetic fabric derived from AMS studies to test either the modern attitude (slight dipping up to 10-15˚) of studied rocks is due to primary paleorelief or the rocks have experienced some tectonic deformations.</span></p>

scholarly journals Mineralogical Constraints on the Potassic and Sodic-Calcic Hydrothermal Alteration and Vein-Type Mineralization of the Maronia Porphyry Cu-Mo ± Re ± Au Deposit in NE Greece

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 182 ◽  
Author(s):  
Vasilios Melfos ◽  
Panagiotis Voudouris ◽  
Margarita Melfou ◽  
Matías G. Sánchez ◽  
Lambrini Papadopoulou ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fluid Phase ◽  
Aqueous Fluid ◽  
Gas Content ◽  
Magmatic Fluid ◽  
Brittle Deformation ◽  
Fluid Circulation ◽  
Magmatic Rocks ◽  
Vein Type ◽  
Host Rocks

The Maronia Cu-Mo ± Re ± Au deposit is spatially related to a microgranite porphyry that intruded an Oligocene monzonite along the Mesozoic Circum-Rhodope belt in Thrace, NE Greece. The magmatic rocks and associated metallic mineralization show plastic and cataclastic features at the south-eastern margin of the deposit that implies emplacement at the ductile-brittle transition, adjacent to a shear zone at the footwall of the Maronia detachment fault. The conversion from ductile to brittle deformation caused a rapid upward magmatic fluid flow and increased the volume of water that interacted with the host rocks through high permeable zones, which produced extensive zones of potassic and sodic-calcic alteration. Potassic alteration is characterized by secondary biotite + K-feldspar (orthoclase) + magnetite + rutile + quartz ± apatite and commonly contains sulfides (pyrite, chalcopyrite, pyrrhotite). Sodic-calcic alteration consists of actinolite + sodic-calcic plagioclase (albite/oligoclase/andesine) + titanite + magnetite + chlorite + quartz ± calcite ± epidote-allanite. The high-oxidation state of the magmas and the hydrothermal fluid circulation were responsible for the metal and sulfur enrichments of the aqueous fluid phase, an increase in O2 gas content, the breakdown of the magmatic silicates and the production of the extensive potassic and sodic-calcic alterations. Brittle deformation also promoted the rapid upward fluid flow and caused interactions with the surrounding host rocks along the high temperature M-, EB-, A- and B-type veins.

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