scholarly journals Petrographical, petrochemical characteristics of Ta Kou massif granitoids, Ham Thuan Nam, Binh Thuan

2020 ◽  
Vol 4 (1) ◽  
pp. First
Author(s):  
Nguyen Thi Thu Thuy ◽  
Nguyen Kim Hoang
Keyword(s):  
Trace Elements ◽  
Chemical Composition ◽  
Potassium Feldspar ◽  
Biotite Granite ◽  
Total Alkalinity ◽  
Magmatic Activity ◽  
High Potassium ◽  
Fine Grained ◽  
Altered Granite ◽  
South Vietnam

Ta Kou is an isometric shape with an area of ​​about 15 km2. Petrographical composition is mainly biotite-hornblende granodiorite; minors are altered light-colored fine-grained biotite granite. Mineral composition is mainly plagioclase 45–50, quartz 25, potassium feldspar 15–20, biotite 5–10, hornblende (5–7); secondary is pyroxen; Accessory minerals include zircon, apatite, orthit, muscovite and rare ore. In some places, near fault or high arch of massif, rocks have been altered by other magma, especially near faults due to post-magma activity including fine-grained biotite granite which caused strongly by alkalization such as increasing the content of potassium felspar (35–50%) and quartz 30; reducing plagioclase content (30–25%); amphibole -colored minerals is rare, and pyroxene is absent. Chemical composition of medium acid granodiorite SiO2 61.08–62.14 (61.85); total alkalinity (K2O+Na2O) 5,99–6,04 (6.00); ratio of alkaline K2O/Na2O: 0.74-0.77 (0.75 <1). Characterized trace elements content of granodiorite: Rb and Ba are low but Sr is quite high; ratios Rb/Sr: 0.24; Ba/Sr 1.40, Ba/Rb: 5.85; K/Rb: 245.39; La/Yb: 10.33; Ce/Yb: 22.11; normal Eu anomalies. When influencing the post-magmatic activity, some granite is more acidific, the chemical composition of altered granite SiO2 72.27–74.07 (73.17); total alkalinity (K2O+Na2O): 7.48–7.96 (7.72); the ratio of alkaline  K2O/Na2O: 1.60–1.69 (1.64>1). Characterized trace elements content of altered granite: Ba and Sr are low but high Rb; ratios of Rb/Sr: 1.43; Ba/Sr: 3.06, Ba/Rb: 2.79; K/Rb: 218.05; La/Yb: 8.60 and Ce/Yb: 15.74; strong Eu anomalies.Ta Kou granitoids belong to the medium to high aluminum series, medium to high potassium alkaline series, negative Eu anomalies are from normal to strong, type of I- granite. Granitoid characterized subduction-related formation and altered, which may be due to the effects of later phase magmatic activity. Compared with granitoid formations in South Vietnam, Ta Kou massif granitoids belong to phase 2 of Định Quán complex.  

scholarly journals Petrographical, petrochemical characteristics of Hòn Rồng massif granitoids, Cam Ranh, Khánh Hòa

2020 ◽  
Vol 3 (3) ◽  
pp. 195-212
Author(s):  
Nguyen Kim Hoang ◽  
Lam Van Phuong
Keyword(s):  
Biotite Granite ◽  
Accessory Mineral ◽  
Chemical Compositions ◽  
Phase 2 ◽  
Phase 3 ◽  
Fine Grained ◽  
South Vietnam ◽  
High K ◽  
Ore Minerals ◽  
Absolute Height

Hòn Rồng massif granitoid has a high mountainous terrain, with an absolute height of 728 m, relatively equal, slightly extended in the Northwest-Southeast direction, occupying an area of ​​about 29 km2. Petrographical composition is mainly medium - grained biotite granite (phase 2), minor is fine- grained biotite granite (phase 3), vein rocks are aplite granite and pegmatite and  a little of xenolith of granodiorite in medium - grained biotite granite. Medium-grained biotite granite: major mineral composition (%): plagioclase (oligoclase) 25–35, quartz 30, orthoclas 25, biotite 5 - 8 and few hornblend; fine-grained granite (%): plagioclase (oligoclase) 30 - 35; quartz 30 - 35; feldspar kali (orthoclase, and microclin) 30, biotite 3 - 5; accessory mineral is zircon, orthite, apatite, sphen, and very little ore minerals (about ​​2%); epimagmatic minerals including: chlorite, epidot, kaolinite, sericite, carbonate, sausorite-replaced association. Rocks are altered alkalization strongly (albitization and microlinization), and minor are chloritization, epidotization and sericitization. Averaged chemical compositions (%)SiO2: 69.07–72.07; total alkali(K2O+Na2O) 7.35–7.96. Ratio of K2O/Na2O 1.04, low TiO2 (0.24–0.37). Ratios of A/CNK 1.02–1.09, Rb/Sr: 0.27–1.62; Ba/Sr: 1.82–2.56, Ba/Rb: 1.58–7.13; K/Rb: 0.42–0.62; Ca/Sr: 0.21–0.47; the value of Eu anomalies is low. Granite belongs to calc-alkaline, aluminum content is from medium to high; K-Na alkaline series, I-granite type. Granitoid had been formed in plutonic - volcanic arc of subduction-zone. Compared with the granitoid formations in South Vietnam territory, Hòn Rồng massif granitoid belongs to phase 2 (main) and phase 3 (minor) of Đèo Cả complex with late Kreta age.

scholarly journals Petrogenesis, Redox State, and Mineralization Potential of Triassic Granitoids in the Mengshan District, South China

2021 ◽  
Vol 9 ◽  
Author(s):  
Yanshen Yang ◽  
Xiaofei Pan ◽  
Zengqian Hou ◽  
Yang Deng ◽  
Yongpeng Ouyang ◽  
...  
Keyword(s):  
Trace Elements ◽  
South China ◽  
Inductively Coupled Plasma ◽  
Redox State ◽  
Evolutionary Process ◽  
Biotite Granite ◽  
Nd Isotopes ◽  
Inductively Coupled ◽  
Fine Grained ◽  
Plasma Mass Spectrometry

The Mengshan district is located in the eastern segment of the Jiangnan Orogen in South China. Multi-phase intrusions were emplaced in this district, with the medium-grained porphyritic biotite granite and its marginal phase (fine-grained porphyritic biotite granite) genetically related to metal and non-metal mineralization. In this study, zircon U–Pb ages and trace elements, whole-rock geochemistry, and Nd isotopes were systematically analyzed for medium- and fine-grained porphyritic biotite granite in the Mengshan district, with the aim of elucidating the origin, evolutionary process, redox state, and mineralization competency of the studied granites. The Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA–ICP–MS) zircon U–Pb dating provided a weighted mean age of 226.6 ± 0.5 to 225.9 ± 0.5 Ma for the studied Mengshan granites, synchronous with the late-episode Triassic magmatism-mineralization in South China. The studied Mengshan granites are high-Si and -K, low-P, and weakly peraluminous, exhibiting features of highly evolved I-type granites. The detailed whole-rock geochemistry and Nd isotopes, and zircon trace elements and Hf isotopes demonstrated that the studied Mengshan granites were likely derived from disequilibrium melting of Proterozoic metamorphic basements that were composed of meta-igneous and metasediments and underwent fractional crystallization of plagioclase, K-feldspar, biotite, Fe-Ti oxide, zircon, and apatite. Low whole-rock K/Rb (&lt;150), Nb/Ta (&lt;6), and Zr/Hf (&lt;26) ratios and the metasomatized rim of zircon also suggest that the melt–fluid interaction occurred during the formation of more evolved fine-grained porphyritic biotite granite. The Mengshan granites have a relatively reduced redox state, revealed by their relatively low whole-rock Fe2O3/FeO ratios (mostly &lt; 0.5), zircon Ce4+/Ce3+ ratios (mostly lower than 90), and oxygen fugacity (below ΔFMQ + 1.4). The data in this study indicate that the Mengshan granites, especially the more evolved fine-grained porphyritic biotite granite, are favorable for W, Sn, Mo (&lt;0.3 Mt), and Cu (&lt;1 Mt) mineralization. Moreover, the contact zone between the fine-grained porphyritic biotite granite (or other Triassic granites) and the Permian Maokou Formation (flint-nodule limestone) is a potential target region for wollastonite exploration.

Research on Process Mineralogy of Potassium-Rich Shale

2010 ◽  
Vol 158 ◽  
pp. 197-203 ◽  
Author(s):  
Jie Liu ◽  
Yue Xin Han ◽  
Wan Zhong Yin
Keyword(s):  
Chemical Composition ◽  
Mineral Composition ◽  
Potassium Feldspar ◽  
Composition Analysis ◽  
Research Results ◽  
Dsc Analyses ◽  
Process Mineralogy ◽  
Mineral Compositions ◽  
Chemical Composition Analysis

The process mineralogy of potassium-rich shale from Chaoyang of Liaoning, China, was studied. Research results showed there are much less variety and smaller quantities in mineral compositions. Calculated mineral composition by means of chemical composition analysis combined with XRD, MLA, IR and TG-DSC analyses showed that main minerals with were Potassium-feldspar, muscovite, biotite and illite, and gangue minerals were quartz and small amounts of hematite. Potassium-rich minerals such as potassium-feldspar and muscovite contact smoothly with quartz respectively, and there was the direction arrangement among potassium-feldspar, quartz and muscovite in the shale. And quartz and hematite were main cement in the shale. The influences of the research results on the potassium extraction from potassium-rich shale were distinct.

The first finding of a Greek amphora in Poland

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sylwester Czopek ◽  
Katarzyna Trybała-Zawiślak ◽  
Joanna Trąbska ◽  
Barbara Trybalska ◽  
Joanna Adamik-Proksa ◽  
...  
Keyword(s):  
Trace Elements ◽  
Forest Steppe ◽  
Iron Compounds ◽  
Fine Grained ◽  
Tof Sims ◽  
First Finding ◽  
High Calcium ◽  
The University ◽  
First Time ◽  
North Western

Abstract In 2017, an expedition of the Institute of Archeology of the University of Rzeszów (Poland) carried out excavations on a hillfort belonging to the Scythian cultural circle (its forest-steppe variant) in Chotyniec, in south-eastern Poland. The hillfort is the central and most important point of a large settlement cluster, which is the furthest north-western enclave of this cultural circle. In an excavated cult object – the so-called ‘zolnik’ – we made an interesting discovery. Here we show this unique finding for the first time: a Greek wine amphora, from the beginning of the sixth century BC. We were able to explore and reconstruct it almost entirely. Amphora is the only artefact of this type found in the present Polish borders. The amphora was subjected to archaeometric research with the use of PLM, SEM/EDS, TXRF and ToF SIMS. The massive fabric was made of high calcium clay enriched in quartz and volcanic lithoclasts. The lack of chromium and nickel among trace elements makes the vessel different from the amphoras from the Eastern Meditteranean analysed so far, suggesting a specific workshop. Red painting was executed with very fine grained iron compounds predominantly based on aluminosilicates, enriched in phosphorus. Obviously, since it is associated with the presence of Scythians in Eastern Europe, it simultaneously delimits (geography-wise) the borders of Greek influence.

scholarly journals Petrogenesis of the synplutonic high-magnesian porphyritic dykes from the mafic-granitoid plutons of the East-European Craton, Voronezh crystalline massif

2019 ◽  
Vol 64 (4) ◽  
pp. 356-371
Author(s):  
R. A. Terentiev
Keyword(s):  
Trace Elements ◽  
Magma Chamber ◽  
Earth Element ◽  
Parent Magma ◽  
Chrome Spinel ◽  
Calc Alkaline ◽  
East European ◽  
Fine Grained ◽  
Mineral Inclusions ◽  
Metasomatized Mantle

This paper documents the data on high-Mg porphyrite dykes (PDs) from the mafic to felsic (~2.09 Ma) plutons of Elan complex (EC). The low-thickness (first centimeters) synplutonic dykes are characterized by sharp straight contacts without visible chilling zones, in contrast to the larger (up to 119 m) dykes that have gradual transitions. The dykes are fresh, porphyritic (bronzite, Al-enstatite, labradorite) and has fine-grained mainly quartzo-feldspathic (+biotite, sulfides, accessories, ±hypersthene) matrix. Based on geochemistry data the PDs are intermediate rocks (SiO2 = 58.9–60.3 wt. %) and plot into calc-alkaline series with high magnesian of whole rock (Mg# ~0.7) and felsic (68.9–70.2 wt. %) matrix (Mg# ~0.5). The PDs show differentiated rare-earth element patterns with negligible Eu anomalies. The bronzite phenocrysts varying sizes are characterized by block zoning and contain irregular inclusions of olivine (Mg# ~0.85), clinopyroxene (Mg# ~0.88), phlogopite (Mg# up to 0.94), labradorite, chrome spinel, graphite and sulfides. The Al-enstatite phenocrysts are practically sterile with respect to trace elements and mineral inclusions. The geochemical features as well as diffusion zones, reaction rims, and resorbed faces of the phenocrysts such as orthopyroxene and plagioclase indicate processes of recrystallization and/or partial dissolution of nonequilibrium crystals in the melt and indicate intratelluric nature of the dyke phenocrysts that cores are inherited from the EC derivatives/cumulate. The mineral thermometry estimates are: (1) the parent magma starting temperatures of 1200–1400 °С and (2) the EC crystallization temperatures 1080–1155 °С, (3) the PD emplacement temperatures 910–1070 °С. The petrogenetic model supposes the generation of EC high-temperature magmas similar to boninites from an upper metasomatized mantle. The melt is contaminated with continental crust lithologies. It implies the half-way evolved magma chamber in the crust. The PD melt, as a result of ending of the half-way magma chamber evolution, was emplaced into the still unheated EC plutons.

scholarly journals PESTRÉ SEDIMENTY OTTNANGU V BRNĚ-KOHOUTOVICÍCH

2018 ◽  
Vol 25 (1-2) ◽  
Author(s):  
Pavla Tomanová Petrová ◽  
David Buriánek ◽  
Karel Kirchner ◽  
Oldřich Krejčí ◽  
František Laufek ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Clay Minerals ◽  
Heavy Fraction ◽  
Parent Rock ◽  
Fine Grained ◽  
Sediment Layers

The reddish coloured sediment layers (up to 5 m thick) were found within building pit in the Brno-Kohoutovice on the Libušina třída Avenue (NW part of Brno). These sediments were assigned to the Ottnangian based on characteristic pseudoassociation of microfossils. Smectite or illite/smectite dominates over kaolinite among the clay minerals. Minerals typomorphic for granitoids of the Brno Massif, i.e. epidote, amphibole and altered titanite, absolutely dominate (99 mod. %) within the assemblage of translucent heavy fraction. Minerals like garnet and staurolite which are typical for the Ottnangian sediments in this region, are presented only in accessoric amount. The chemical composition of the studied sediments is located between the chemical composition of granodiorites of the Brno Massif and Neogene clays. Relatively high content of Zr, Hf and HREE, which is interpreted as result of presence of very fine grained zircon in studied sediments, is characteristic. High content of SiO2 and comparatively low contents of Al2O3 and Fe2O3 indicates non-lateritic type of weathering. The chemical composition of studied sediments reflects semiarid to humid paleoclimate that the granitoids of the Brno Massif as parent rock have undergone.

scholarly journals Synrift sandstones and clayey rocks: bulk chemical composition and location on a number of discriminant paleogeodynamic diagrams

2019 ◽  
pp. 439-465
Author(s):  
A. V. Maslov ◽  
V. N. Podkovyrov ◽  
E. Z. Gareev ◽  
A. D. Nozhkin
Keyword(s):  
Chemical Composition ◽  
Continental Margins ◽  
Bulk Chemical Composition ◽  
East European ◽  
Fine Grained ◽  
Sedimentary Deposits ◽  
Data Points ◽  
Bulk Chemical ◽  
Clayey Rocks ◽  
Active Continental Margins

The bulk chemical composition of synrift sandstones and associated clayey rocks has been analized, and the distribution of the fields they form has been studied on discriminant paleogeodynamic SiO2K2O/Na2O [Roser, Korsch, 1986] and DF1DF2 [Verma, Armstrong-Altrin, 2013] diagrams. The studied sandstones in terms of bulk chemical composition mainly correspond to greywacke, lititic, arkose and subarkose psammites; Sublitites and quartz arenites are also found. A significant part in the analyzed data massif consists of psammites, in which log(Na2O/K2O)-1.0; missing on the Pettijohn classification chart. This confirms our conclusion, based on the results of mineralogical and petrographic studies, that the sedimentary infill of rift structures unites immature sandstones, the detrital framework of which was formed due to erosion of local sources, represented by various magmatic and sedimentary formations. Synrift clayey rocks, compared with sandstones, are composed of more mature fine-grained siliciclastics. As follows from the distribution of figurative data points of clayey rocks on the F1F2 diagram [Roser, Korsch, 1988], its sources were mainly sedimentary deposits. The content of most of the main rock-forming oxides in the synrift sandstones is almost the same as in silt-sandstone rocks present in the Upper Precambrian-Phanerozoic sedimentary mega-complex of the East European Plate, but at the same time differs significantly from the Proterozoic and Phanerozoic cratonic sediments, as well as from the average composition upper continental crust. It is shown that the distribution of the fields of syntift sandstones and clayey rocks on the SiO2K2O/Na2O diagram does not have any distinct features, and their figurative data points are localized in the areas of terrigenous rocks of passive and active continental margins. On the DF1DF2 diagram, the fields of the studied psammites and clayey rocks are located in areas of riftogenous and collisional environments. We have proposed a different position of the border between these areas in the diagram, which will require further verification.

The type section of the Codell Sandstone

2021 ◽  
Vol 58 (3) ◽  
pp. 211-248
Author(s):  
James Hagadorn ◽  
Mark Longman ◽  
Richard Bottjer ◽  
Virginia Gent ◽  
Christopher Holm-Denoma ◽  
...  
Keyword(s):  
Surface Expression ◽  
Potassium Feldspar ◽  
Detrital Zircons ◽  
Niobrara Formation ◽  
Denver Basin ◽  
Fine Grained ◽  
Type Section ◽  
Fossil Fish ◽  
Fish Teeth ◽  
Reference Section

We formally assign, describe and interpret a principal reference section for the middle Turonian Codell Sandstone Member of the Carlile Shale near Codell, Kansas. This section, at the informally named Pumpjack Road, provides the thickest surface expression (9 m, ~30 ft) of the unit in Ellis County. The outcrop exposes features that typify the Codell throughout the southern Denver Basin and vicinity. At this reference section, the Codell conformably overlies the Blue Hill Shale Member of the Carlile Shale and is unconformably overlain by the Fort Hays Limestone Member of the Niobrara Formation or locally by a thin (<0.9 m, <3 ft) discontinuous mudstone known as the Antonino facies. The top contact of the Codell is slightly undulatory with possible compaction features or narrow (<30.5 m, <100 ft), low-relief (0.3-0.6 m, 1-2 ft) scours, all of which hint that the Codell is a depositional remnant, even at the type section. At Pumpjack Road, the Codell coarsens upward from a recessive-weathering argillaceous medium-grained siltstone with interbedded mudstone at its base to a more indurated cliff-forming muddy, highly bioturbated, very fine-grained sandstone at its top. The unit contains three informal gradational packages: a lower Codell of medium to coarse siltstone and mudstone, a middle Codell of muddy coarse siltstone, and an upper muddy Codell dominated by well-sorted very fine-grained sandstone. The largest grain fractions, all <120 mm in size, are mostly quartz (40-80%), potassium feldspar (7-12%), and albite (1-2%), with some chert (<15%), zircon, and other constituents such as abraded phosphatic skeletal debris. Rare fossil fish teeth and bones also occur. Detrital and authigenic clays make up 9 to 42% of the Codell at the reference section. Detrital illite and mixed layer illite/smectite are common, along with omnipresent kaolinite as grain coatings or cement. As is typical for the Codell, the sandstone at the type section has been pervasively bioturbated. Most primary structures and bedding are obscured, particularly toward the top of the unit where burrows are larger, deeper and more diverse than at its base. This bioturbation has created a textural inversion in which the larger silt and sand grains are very well sorted but are mixed with mud. Detrital zircons from the upper Codell are unusual in that they are mostly prismatic to acicular, euhedral, colorless, unpitted, and unabraded, and have a near-unimodal age peak centered at ~94 Ma. These characteristics suggest they were reworked mainly from Cenomanian bentonites; their ultimate source was likely from the Cordilleran orogenic belt to the west and northwest.

Trace elements and Pb isotope composition of annual tree rings and pine needles growing in highly industrialized region in southern Poland

2021 ◽  
Author(s):  
Barbara Sensuła ◽  
Nathalie Fagel
Keyword(s):  
Trace Elements ◽  
Chemical Composition ◽  
Tree Rings ◽  
Wet Deposition ◽  
Isotope Ratio ◽  
Isotope Composition ◽  
Pine Needles ◽  
Pb Isotope ◽  
Southern Poland ◽  
Icp Ms

&lt;p&gt;Trees can provide annual records of ecosystem changes connected with human activity over several decades. These changes can be recorded in the pattern of variation of tree-rings widths and in the variation in the elemental composition of wood. Analysis of trace metal pollution is based on the assumption that element concentrations in tree foliage and tree rings represent element availability in the environment.&lt;/p&gt;&lt;p&gt;We determined the chemical composition of pine needles and annual tree rings to monitor environmental contamination in an urban forest environment in the most industrialized part of southern Poland.&lt;/p&gt;&lt;p&gt;The concentrations of trace elements (Cr, Co, Ni, Cu, Zn, Pb) and the Pb isotope composition were measured in needles from&amp;#160;Pinus sylvestris&amp;#160;L. growing in nine urban forests near five factories. Trace elemental concentration and Pb isotope ratio were determined by ICP-MS and MC-ICP-MS, respectively. The needles were characterized based on the concentrations of Cr, ranging from 0.05 to 0.7 mg/kg, Co, from 0.005 to 0.075 mg/kg, Ni, from 0.12 to 0.66 mg/kg, Cu, from 0.49 to 1.0 mg/kg, Zn, from 3.9 to 14 mg/kg, and Pb, from 0.06 to 0.53 mg/kg. The&amp;#160;&lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;206&lt;/sup&gt;Pb ratio ranged from 2.08 to 2.11 and the&amp;#160;&lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;207&lt;/sup&gt;Pb ratio between 1.15 and 1.17. The heterogeneity of Pb isotope ratio indicates that there are different sources affecting the Pb isotopic composition of pine needles (Sensu&amp;#322;a et al., 2021).&lt;/p&gt;&lt;p&gt;In one of the investigated site, a radial trace-element profiles were determined by Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (Laser ablation: New Wave Research UP-193 FX Fast Excimer, ICP-MS: Thermo Scientific X-Series2 with CCT -Collision Cell Technology) at Royal Museum for Central Africa (Belgium). LA-ICP-MS provides a repeatable, minimally destructive, sensitive method for determining many elements in wood tissue, with relatively high spatial resolution.Temporal variations of element concentration (median) in annual tree-rings of pines were compared with time series of wet deposition of pollutant and air pollutant concentration in the investigated area.&amp;#160;The similar trends of magnitudes changes can be observed between analysed elements concentration (Na, Mg, Fe, Ni, Zn) and total wet deposition of these elements in the environment during vegetation period or these elements concentration in the rain (Sensu&amp;#322;a et al. 2017).&amp;#160;&lt;/p&gt;&lt;p&gt;Different space-time patterns of element accumulation in pine needles and annaul tree rings were observed. The variation in isotopic composition reflects a mix between different anthropogenic sources.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Sensu&amp;#322;a, B., Wilczy&amp;#324;ski, S., Monin, L., Allan, M., Pazdur, A., &amp; Fagel, N. (2017). Variations of tree ring width and chemical composition of wood of pine growing in the area nearby chemical factories,&amp;#160;Geochronometria,&amp;#160;44(1), 226-239. doi:&amp;#160;https://doi.org/10.1515/geochr-2015-0064&lt;/p&gt;&lt;p&gt;Sensu&amp;#322;a, B., Fagel, N., &amp; Michczy&amp;#324;ski, A. (2021). Radiocarbon, trace elements and pb isotope composition of pine needles from a highly industrialized region in southern Poland.&amp;#160;Radiocarbon,&amp;#160;1-14. doi:10.1017/RDC.2020.132&lt;/p&gt;

Nouvelles observations sur les roches vertes de l'anticlinal de Laniscat-Merleac (Cotes-du-Nord)

1963 ◽  
Vol S7-V (5) ◽  
pp. 844-851 ◽  
Author(s):  
Jean Nicolas ◽  
Jean Paul Sagon
Keyword(s):  
Chemical Composition ◽  
Chemical Analysis ◽  
Rock Sample ◽  
Coarse Grained ◽  
Northern Flank ◽  
Fine Grained ◽  
Rock Supports

Abstract Observations on the dolerites of the northern flank of the E-W-trending Laniscat-Merleac anticline in NW France suggest that the rocks were emplaced as coulees. A well-marked granular differentiation in the rock supports this hypothesis; the coarse-grained rocks are in contact with Devonian rocks at the bottom of the coulee and the fine-grained rocks are in contact with Dinantian rocks at the top. Chemical analysis shows that there is a diminishing of Na &lt;sub&gt;2&lt;/sub&gt; O and an augmentation of the percentage of CaO ranging from the boundary of the coarse-grained rock to that of the fine-grained. Overlying the green rocks are green schists of comparable chemical composition attributed to former tuffs which were subject to regional epimetamorphism. Finally, a coarse-grained, green rock sample has been traced to the spilite family.

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