scholarly journals Geochemistry and Mineralization of Some Selected Pegmatite Deposits in Panda North Central, Nigeria

2021 ◽  
Vol 6 (2) ◽  
pp. 58-66
Author(s):  
I. Y. Tanko ◽  
P. Chime
Keyword(s):  
Continental Crust ◽  
Rare Metal ◽  
Major Elements ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
North Central ◽  
Rock Types ◽  
Alkaline Environments ◽  
Discrimination Diagram ◽  
Lithologic Unit

Pegmatite constitutes an important lithologic unit in the Precambrian Basement Complex of Panda north central Nigeria. The primary aim of this study is to present a geochemical data of various rock types in the area especially pegmatite in order to determine their geochemical classification and mineralization potential of some selected pegmatite deposits in the area. Geochemical analysis reveals that the pegmatite samples have high SiO2 content; 73.8-94.8 wt%, low Na2O/K2O ratio suggesting they are strongly peralkaline and peraluminous, indicating that the pegmatite may have formed from mixed plutonic sources. The discrimination diagram of TiO2 versus SiO2 shows that the samples plotted on both igneous and sedimentary field, but majorly on the igneous field which is an implication that substantial material may have been generated from igneous sources. Also the plotting of the pegmatite samples in both the tholeiitic and calc-alkaline fields shows that the magma from which the rock was formed was not totally restricted in occurrence only to subduction related environment but also from the oceanic crust of calc-alkaline environments. This is further confirmed by discrimination diagrams plot of TiO2-K2O-P2O which indicates that substantial samples plotted fall within the continental crust. High potash content alkalies with relative Fe-enrichment and silica suggest the plutonic generation of magma and the development of the rocks in both the oceanic and continental crust. Major elements analysis of both the granitic rock aplite and biotite gneiss shows moderately high silica values. These values reflect the geochemical characteristic of crystalline rocks. The pegmatite of the study area exhibits low contents of Nb, Ta, Ga, Rb and Sn which are the major mineralization indices for pegmatite bodies. In classifying the pegmatites, rare metal indicative elements were used to discriminate the barren ones from the mineralized. A plot of Ta-Ga reveals that all the samples plotted are below the boundary of mineralization line, suggesting all the pegmatite samples in the study area to be barren in term of rare earth metals and can be compared to other pegmatite bodies in Nigeria and around the world.

Pétrologie des roches volcaniques du sillon de roches vertes archéennes de Matagami – Chibougamau à l'ouest de Chapais (Abitibi est, Québec).1. Le groupe basal de Roy

1986 ◽  
Vol 23 (4) ◽  
pp. 561-578 ◽  
Author(s):  
Christian Picard ◽  
Michel Piboule
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Fractional Crystallization ◽  
Mantle Source ◽  
Hot Spot ◽  
Lateral Spreading ◽  
Geochemical Data ◽  
Spinel Lherzolite ◽  
Calc Alkaline ◽  
Mantle Sources

In the northeastern part of the Abitibi orogenic belt, the Archean Matagami–Chibougamou greenstone belt (2700 Ma) includes a basal volcanic sequence named the Roy Group, unconformably overlain by a volcano-sedimentary series called the Opemisca Group.The Roy Group, to the west of the town of Chapais, consists of a thick, stratified, and polycyclic volcanic series (thickness = 11 000 m) resembling the large, western Abitibi submarine stratovolcanoes constructed by three mafic to felsic magmatic cycles. The first cycle (Chrissie Formation) shows lateral spreading and is composed only of a meta-andesite and felsic pyroclastite sequence of calc-alkaline affinity. The other two cycles (Obatogamau and Waconichi formations; then Gilman, Blondeau, and Scorpio formations) are characterized by a sequence of repeated MORB type basaltic lava flows of tholeiitic affinity and by intermediate to acid lava and pyroclastic sequences calc-alkaline affinity.The stratigraphic and petrographic data suggest emplacement of mafic lavas on an abyssal plain (Obatogamau Formation) or at a later time on the flanks of a large submarine volcanic shield (Gilman and Blondeau formations). The lava and felsic pyroclastite flows were formed by very explosive eruptions from central spreading type volcanoes above a pre-existing continental crust. In particular, the Scorpio volcanic rocks were emplaced on volcanic islands later dismantled by erosion.The contents and distribution of trace elements and rare earths show that basaltic lavas resulted from an equilibrium partial melting (F = 15–35%) of spinel lherzolite type mantle sources depleted to weakly enriched in Th, Ta, Nb, and light rare-earth elements (LREE), and from fractional crystallization at low pressure of feldspar, clinopyroxene, and olivine. The lavas and the felsic pyroclastites of the Waconichi and Scorpio formations appear to result from partial melting of a mantle source of lherzolite type enriched in LREE and involving some garnet. At a late stage, the melts were probably contaminated by some continental crust materials and then differentiated by fractional crystallization of plagioclase, amphibole, biotite, and magnetite. The lavas in the Chrissie Formation and the middle member of the Gilman Formation seem to result from partial melting of a mantle source enriched in LREE with a composition between the two described above. They were subsequently modified by fractional crystallization of the plagioclase, clinopyroxene, olivine, and titanomagnetite.In general, the mafic to felsic magmatic cycles observed are characterized by a thick sequence of repeated tholeiitic basalt flows similar to those of modern mid-oceanic ridges and by a lava and felsic pyroclastite sequence of calc-alkaline affinity comparable to those occurring in orogenic belts. The transition from one lava sequence to another is marked by a significant chemical discontinuity, and the mantle sources exhibit an increasing enrichment in LREE during a given magmatic cycle. A model is proposed to satisfactorily explain all the stratigraphic, petrographic, and geochemical data implying a hot spot type mechanism, which could be responsible for the cyclic, rising diapirs inside the stratified Archean mantle and for initiating the repeated mantle source meltings, depleted and enriched in LREE, respectively. [Journal Translation]

scholarly journals Origin of quartzo-feldspathic supracrustal rocks from the central part of the Nagssugtoqidian Mobile Belt of West Greenland

1984 ◽  
Vol 117 ◽  
pp. 1-26
Author(s):  
A Rehkopff
Keyword(s):  
Granulite Facies ◽  
Major Elements ◽  
Thin Layers ◽  
Mobile Belt ◽  
Calc Alkaline ◽  
Rock Types ◽  
Metavolcanic Rocks ◽  
The Individual ◽  
Metaigneous Rocks ◽  
Discrimination Methods

The Marranguit-Kangilerssua supracrustals constitute a sequence of variable supracrustallithologies intensely folded into surrounding orthogneisses and metamorphosed under granulite facies conditions. No field or petrographic evidence indicates the original nature of the individual supracrustal rock types. Fortynine samples from the quartzo-feldspathic part of the supracrustals have been analysed for major elements and the trace elements Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr and Ba. Ten different geochemical discrimination methods indicate that both metasedimentary and metaigneous material are present. The metaigneous rocks possess typical calc-alkaline differentiation trends and were originally extrusives. Mixing-zones between metasedimentary and metavolcanic material are interpreted as reflecting a pyroclastic nature of some of the metavolcanic rocks. The quartzo-feldspathic part of the M-K supracrustals is dominated by greywacke/lithic arenite with subordinate intercalations of mudstone and single layers or lensoid bodies of subarkose and sublithic arenite. The greywacke/lithic arenite grade into calc-alkaline pyroclastics, which vary in composition from rhyodacite to rhyolite. Associated quartz-andesitic and dacitic extrusives occur throughout the supracrustal formation, which in addition contains thin layers af limestone, basic and ultrabasic rocks. The supracrustals may be either Archaean or Proterozoic in age.

scholarly journals Geology and Petrogenesis of Igneous Rocks from Batur Paleovolcano, Gunungkidul, Yogyakarta: Evidence from their Textures, Mineralogy, and Major Elements Geochemistry

2019 ◽  
Vol 4 (1) ◽  
pp. 32
Author(s):  
Fahmi Hakim ◽  
Yanuardi Satrio Nugroho ◽  
Cendi Diar Permata Dana ◽  
Anastasia Dewi Titisari
Keyword(s):  
Tectonic Setting ◽  
Research Area ◽  
Major Elements ◽  
Geological Mapping ◽  
Igneous Rocks ◽  
Emission Spectrometry ◽  
Geochemical Data ◽  
Geological Condition ◽  
Calc Alkaline ◽  
Andesite Lava

Batur paleovolcano is located in Wediombo Beach area, Gunungkidul Regency, Yogyakarta and is being part of Wuni Formation. Several volcanic products including lava flow, autoclastic breccia and volcanic breccia can be found associated with diorite intrusions. This research is aimed to characterize geological, mineralogical andgeochemical variations of igneous rocks from Batur paleovolcano to understand its petrogenesis. Detailed geological mapping with scale of 1:12,500 is conducted to identify geological aspects and delineate igneous rocks distributions. Igneous rocks and selected wall rocks samples were prepared for laboratory analysis including 8 samples for petrography and 5 samples for ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Several geochemical data from previous study are also added to investigate the geochemical variations. Geological condition of the research area consists of four rock units including colluvial deposit, limestone, andesite lava and diorite intrusion. Geological structures found are normal fault and shear joint where the main stress direction is north–south. Petrography analysis showed that igneous rocks in this research area consist of diorite intrusion and andesite lava with phorphyritic texture. Plagioclase become the most abundant minerals found both as phenocryst phase and groundmass. Hornblende only occur as phenocryst phase in minor amounts as accesory mineral. Major elementsgeochemistry analysis showed the rocks are characterized by intermediate silica with low alkali content. They are can be categorized as calc-alkaline series. However, some samples are fall into tholeiitic series. Major elements variation and textural study also indicate the magma is experienced differentiation process by fractional crystallization mechanism. This study suggests that igneous rocks from Batur paleovolcano is formed by two phases of formation. Earlier phase is the formation of andesite lava in island arc tholeiitic tectonic setting then at the later phase is formation of diorite intrusion in the calc-alkaline basalts tectonic setting.

Pétrologie des roches volcaniques de sillon de roches vertes archéennes de Matagami–Chibougamau à l'ouest de Chapais (Abitibi est, Québec), 2. Le groupe hautement potassique d'Opémisca

1986 ◽  
Vol 23 (8) ◽  
pp. 1169-1189 ◽  
Author(s):  
Christian Picard ◽  
Michel Piboule
Keyword(s):  
Fractional Crystallization ◽  
Crustal Contamination ◽  
Major Elements ◽  
Geochemical Data ◽  
Continental Margins ◽  
Garnet Lherzolite ◽  
Calc Alkaline ◽  
Volatile Elements ◽  
High K ◽  
Active Continental Margins

In the western part of the Chapais syncline (Abitibi East, Quebec), the Opemisca Group unconformably overlies the Roy Group at a low angle. It consists of a thick turbidite sequence covered by an interdigitated sequence of lavas and alluvial cone sediments. The subaerial lavas include two sequences evolving from porphyric metabasalts to metatrachyandesites and porphyric metatrachytes (lower sequence) or to K-rich aphanitic meta-andesites (upper sequence). These lavas, with calc-alkaline to shoshonitic affinity, have high K2O, Ba, Sr, and Th contents and show highly enriched LREE spectra.The behaviour of major elements, trace elements, and lanthanides suggests an origin from partial melting of a mantle source consisting of a garnet lherzolite enriched in K, Sr, Rb, Ba, and Th by volatile elements and also by crustal contamination and by fractional crystallization mechanisms. The evolution of the lavas of the lower sequence, progressively deficient in Y, seems to have been controlled by fractional crystallization of a plagioclase, clinopyroxene, and olivine mixture; this was followed for the metatrachyandesites and metatrachytes by high H2O activity of a feldspar, amphibole, titanomagnetite, and apatite mixture. The evolution of lavas enriched in Y in the upper sequence seems to have been controlled by weak H2O activity of the anhydrous plagioclase, clinopyroxene, and olivine assemblage.The petrographic and geochemical data suggest an emplacement similar to that occurring on the active continental margins of the central Andes and implies the existence of a late-stage ensialic arc. [Translated by the journal]

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

scholarly journals Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 99-119 ◽  
Author(s):  
SILVIA R. MEDEIROS ◽  
CRISTINA M. WIEDEMANN-LEONARDOS ◽  
SIMON VRIEND
Keyword(s):  
Partial Melting ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Tholeiitic Magma ◽  
Rock Types ◽  
Upper Proterozoic ◽  
Incompatible Elements ◽  
Wide Range ◽  
Intermediate Rock

At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

scholarly journals Non-subduction petrological mechanisms for the growth of the neoarcheam continental crust of the Kola–Norwegian terrane, Fennoscandian shield: geological and isotope-geochemical evidence

2019 ◽  
Vol 27 (2) ◽  
pp. 161-186
Author(s):  
A. B. Vrevskii
Keyword(s):  
Continental Crust ◽  
Greenstone Belt ◽  
Geochemical Modeling ◽  
Volcanic Rocks ◽  
Fennoscandian Shield ◽  
Crustal Growth ◽  
Calc Alkaline ◽  
Geochemical Evidence

The paper reports new data on the composition and age of the Neoarchean calc-alkaline volcanic rocks of the Uraguba–Kolmozero–Voron’ya greenstone belt (UKV GB). Petrological-geochemical modeling indicates a polygenetic origin of primary melts of the basalt–andesite–dacite association and non-subduction geodynamic mechanisms for the crustal growth in the largest greenstone belt of the Kola–Norwegian Block of the Fennoscandian shield.

Exemples de mélange de magmas en contexte plutonique: les enclaves des tonalites–granodiorites du massif de Bono (Sardaigne septentrionale)

1989 ◽  
Vol 26 (6) ◽  
pp. 1264-1281 ◽  
Author(s):  
C. Cocirta ◽  
J. B. Orsini ◽  
C. Coulon
Keyword(s):  
Geochemical Data ◽  
Mixing Process ◽  
Calc Alkaline ◽  
Specific Group ◽  
Mineralogical Analysis ◽  
Magmatic Origin ◽  
Interaction Mechanisms ◽  
Compositional Variations ◽  
End Members ◽  
Host Rocks

In calc-alkaline orogenic plutons, the dark xenoliths and their host rocks must be considered the expression of partial mixing of magma.Three associations of this type have been investigated and are illustrated by the Bono pluton (northern Sardinia)— a composite pluton including three intrusives of different nature (tonalitic to granodioritic) and containing a very large number of basaltic xenoliths of magmatic origin. Detailed mineralogical analysis of the two end members in each association, coupled with geochemical data, has determined the major petrogenetic mechanisms intervening in the mixing process in a plutonic setting: temperature equilibration, mechanical exchanges of crystals, chemical exchanges, etc. The most important result of this article, however, is to show that each intrusion is related to a specific group of xenoliths that is characterized by constant FeOt/MgO. The latter reflects the different composition of basaltic components, and it is concluded that each intrusive event is associated with a unique mixing episode. As in volcanic settings, the mixing process may have initiated the intrusion.The extreme compositional variations in the magmatic xenoliths, recognized in several series of orogenic plutons, is explained here by different initial basaltic end members and by variation in the intensity of the interaction mechanisms. [Journal Translation]

Release of Uranium from Uraninite in Granites Through Alteration: Implications for the Source of Granite-Related Uranium Ores

2021 ◽  
Author(s):  
Long Zhang ◽  
Zhenyu Chen ◽  
Fangyue Wang ◽  
Noel C. White ◽  
Taofa Zhou
Keyword(s):  
Uranium Concentration ◽  
Geochemical Data ◽  
Uranium Deposits ◽  
Bulk Rock ◽  
Calc Alkaline ◽  
Alkaline Granite ◽  
Compositional Evolution ◽  
High K ◽  
Backscattered Electron ◽  
Uranium Sources

Abstract Uraninite is the main contributor to the bulk-rock uranium concentration in many U-rich granites and is the most important uranium source for granite-related uranium deposits. However, detailed textural and compositional evolution of magmatic uraninite in granites during alteration and associated uranium mobilization have not been well documented. In this study, textures and geochemistry of uraninites from the Zhuguangshan batholith (South China) were investigated by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The geochemical data indicate that the Longhuashan and Youdong plutons are peraluminous leucogranite, the Changjiang pluton is highly fractionated high-K calc-alkaline granite, and the Jiufeng pluton belongs to a high-K calc-alkaline association. Uraninites from the Longhuashan and Youdong granites have lower concentrations of ThO2 (0.9–4.0 wt %) and rare earth elements (REE)2O3 (0.1–1.0 wt %) than those from the Changjiang and Jiufeng granites (ThO2 = 4.4–7.6 wt %, REE2O3 = 0.7–5.1 wt %). Uraninites observed in the Longhuashan, Youdong, Changjiang, and Jiufeng granites yielded chemical ages of 223 ± 3, 222 ± 2, 157 ± 1, and 161 ± 2 Ma, respectively. The samples (including altered and unaltered) collected from the Longhuashan, Youdong, and Changjiang granites are characterized by highly variable whole-rock U concentrations of 6.9 to 44.7 ppm and Th/U ratios of 0.9 to 7.0, consistent with crystallization of uraninite in these granites being followed by uranium leaching during alteration. Alteration of uraninite, indicated by altered domains developing microcracks and appearing darker in backscattered electron (BSE) images compared to unaltered domains, results in the incorporation of Si and Ca and mobilization of U. In contrast, the least altered samples of the unmineralized Jiufeng granite have low U concentrations (5.3–16.4 ppm) and high ΣREE/U (13.6–49.4) and Th/U ratios (2.1–5.6), which inhibit crystallization of uraninite, as its crystallization occurs when the U concentration is high enough to exceed the substitution capacity of other U-bearing minerals. These results indicate that the Longhuashan, Youdong, and Changjiang granites were favorable uranium sources for the formation of uranium deposits in this area. This study highlights the potential of uraninite alteration and geochemistry to assist in deciphering uranium sources and enrichment processes of granite-related uranium deposits.

Petrographic, Geochemical and Isotopic (Sr–Nd–Pb–Os) Study of Plio-Quaternary Volcanics and the Tertiary Basement in the Jorullo-Tacámbaro Area, Michoacán-Guanajuato Volcanic Field, Mexico

2019 ◽  
Vol 60 (12) ◽  
pp. 2317-2338 ◽  
Author(s):  
Marie-Noëlle Guilbaud ◽  
Claus Siebe ◽  
Christine Rasoazanamparany ◽  
Elisabeth Widom ◽  
Sergio Salinas ◽  
...  
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Volcanic Belt ◽  
Volcanic Field ◽  
Calc Alkaline ◽  
Trace Element Pattern ◽  
Alkaline Rocks ◽  
Rock Types ◽  
Oceanic Sediments ◽  
Element Pattern

Abstract The origin of the large diversity of rock types erupted along the subduction-related Trans-Mexican Volcanic Belt (TMVB) remains highly debated. In particular, several hypotheses have been proposed to explain the contemporary eruption of calc-alkaline and alkaline magmas along the belt. The Michoacán-Guanajuato Volcanic Field (MGVF) is an atypical, vast region of monogenetic activity located in the western-central part of the TMVB. Here we present new petrographic, geochemical, and isotopic (Sr–Nd–Pb–Os) data on recent volcanics in the Jorullo-Tacámbaro area that is the closest to the oceanic trench. TMVB-related volcanics in this area are Plio-Quaternary (<5 Ma) and mainly form a calc-alkaline series from basalts to dacites, with rare (<5 vol. %) alkaline rocks that range from trachybasalts to trachydacites, and transitional samples. Crystal textures are consistent with rapid crystallization at shallow depth and processes of mixing of similar magma batches (magma recharge). All of the samples exhibit an arc-type trace element pattern. Alkaline and transitional magmas have higher Na2O and K2O, lower Al2O3, and higher concentrations in incompatible elements (e.g. Sr, K, Ba, Th, Ce, P) compared to calc-alkaline rocks. Calc-alkaline rocks are similar isotopically to transitional and alkaline samples, except for a few low 87Sr/86Sr samples. Sr, Nd and Pb isotopes do not correlate with MgO or 187Os/188Os, indicating that they were not significantly influenced by crustal contamination. Isotopic and trace-element systematics suggest that the Tacámbaro magmas are produced by melting of a mantle wedge fluxed by fluids derived from a mixture of subducted sediments and altered oceanic crust. Alkaline and transitional magmas can be derived from a lower degree of partial melting of a similar source to that of the calc-alkaline rocks, whereas the few low 87Sr/86Sr calc-alkaline rocks require a lower proportion of fluid derived from oceanic sediments and crust. Volcanism at the trenchward edge of the MGVF was thus driven purely by subduction during the last 5 Ma, hence discarding slab rollback in this sector of the TMVB.

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