scholarly journals Petrography and Geochemical Characterization of a Granite Batholith in Idanre, Southwestern Nigeria

2021 ◽  
Vol 50 (2) ◽  
pp. 315-326
Author(s):  
Oluwatoyin O. Akinola ◽  
Azman A. Ghani ◽  
Elvaene James
Keyword(s):  
Calc Alkaline ◽  
Southwestern Nigeria ◽  
Geochemical Characterization ◽  
Fine Grained ◽  
Rock Types ◽  
Pan African ◽  
High K ◽  
Granite Batholith ◽  
Type Granite

Idanre granite batholith in southwestern Nigeria contain three rock types, namely, Older granite undifferentiated (OGu), Older granite porphyritic (OGp) and Older granite fine-grained (OGf). The granitoids intruded into a basement rock of primarily migmatite gneiss. Petrography indicates that quartz, orthoclase, hornblende, and biotite are common to all members while microcline is more prominent in OGp and plagioclase is poorly represented in OGf. Despite minor differences in petrographic features, the granite units generally have similar geochemical relationships. The average SiO2 contents in OGp (70.49%), OGu (68.7%) and OGf (65.8%) are comparable to similar Pan-African suites located in eastern and northern Nigeria. Na2O+K2O-CaO versus SiO2 diagram shows all the granite members are calcic, K2O vs SiO2 plot classify the granites as high-K calcic alkali to shoshonitic. ANK vs ACNK plot indicatesthey are peraluminous. Plot of A/CNK vs SiO2 and K2O vs Na2O diagrams classified the rock as S-type granite. The granitoids are calc-alkaline with elevated Na2O (>2.6%) and Al/(Na2O+CaO) contents (OGu, 2.1-3.4; OGp, 2.4-3.1 and OGf, 2.2-2.9). The tectonic diagram (Rb vs (Y+Nb) indicatesthatthe batholith is Within Plate Granite (WPG.

Petrological and geochemical characterization of the arc-related Suru–Thasgam ophiolitic slice along the Indus Suture Zone, Ladakh Himalaya

2021 ◽  
pp. 1-20
Author(s):  
I.M. Bhat ◽  
T. Ahmad ◽  
D.V. Subba Rao ◽  
N.V. Chalapathi Rao
Keyword(s):  
Suture Zone ◽  
Secondary Mineral ◽  
High Field Strength ◽  
Geochemical Characterization ◽  
Rock Types ◽  
Ladakh Himalaya ◽  
Magnesian Olivine ◽  
Textural Relationship ◽  
Ree Patterns

Abstract The Ladakh Himalayan ophiolites preserve remnants of the eastern part of the Neo-Tethyan Ocean, in the form of Dras, Suru Valley, Shergol, Spongtang and Nidar ophiolitic sequences. In Kohistan region of Pakistan, Muslim Bagh, Zhob and Bela ophiolites are considered to be equivalents of Ladakh ophiolites. In western Ladakh, the Suru–Thasgam ophiolitic slice is highly dismembered and consists of peridotites, pyroxenites and gabbros, emplaced as imbricate blocks thrust over the Mesozoic Dras arc complex along the Indus Suture Zone. The Thasgam peridotites are partially serpentinized with relict olivine, orthopyroxene and minor clinopyroxene, as well as serpentine and iron oxide as secondary mineral assemblage. The pyroxenites are dominated by clinopyroxene followed by orthopyroxene with subordinate olivine and spinel. Gabbros are composed of plagioclase and pyroxene (mostly replaced by amphiboles), describing an ophitic to sub-ophitic textural relationship. Geochemically, the studied rock types show sub-alkaline tholeiitic characteristics. The peridotites display nearly flat chondrite-normalized rare earth element (REE) patterns ((La/Yb)N = 0.6–1.5), while fractionated patterns were observed for pyroxenites and gabbros. Multi-element spidergrams for peridotites, pyroxenites and gabbros display subduction-related geochemical characteristics such as enriched large-ion lithophile element (LILE) and depleted high-field-strength element (HFSE) concentrations. In peridotites and pyroxenites, highly magnesian olivine (Fo88.5-89.3 and Fo87.8-89.9, respectively) and clinopyroxene (Mg no. of 93–98 and 90–97, respectively) indicate supra-subduction zone (SSZ) tectonic affinity. Our study suggests that the peridotites epitomize the refractory nature of their protoliths and were later evolved in a subduction environment. Pyroxenites and gabbros appear to be related to the base of the modern intra-oceanic island-arc tholeiitic sequence.

The Pan-African high-K calc-alkaline peraluminous Elat granite from southern Israel: geology, geochemistry and petrogenesis

2004 ◽  
Vol 40 (3-4) ◽  
pp. 115-136 ◽  
Author(s):  
M. Eyal ◽  
B.A. Litvinovsky ◽  
Y. Katzir ◽  
A.N. Zanvilevich
Keyword(s):  
Calc Alkaline ◽  
Pan African ◽  
High K

scholarly journals Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)

2020 ◽  
Vol 191 ◽  
pp. 34 ◽  
Author(s):  
Félix Djerossem ◽  
Julien Berger ◽  
Olivier Vanderhaeghe ◽  
Moussa Isseini ◽  
Jérôme Ganne ◽  
...  
Keyword(s):  
Geothermal Gradient ◽  
Isotopic Signature ◽  
Biotite Granite ◽  
Granite Sample ◽  
Metasedimentary Rocks ◽  
Rock Types ◽  
Pan African ◽  
High K ◽  
Back Arc ◽  
Lower Crustal

This paper presents new petrological, geochemical, isotopic (Nd) and geochronological data on magmatic rocks from the poorly known southern Ouaddaï massif, located at the southern edge of the so-called Saharan metacraton. This area is made of greenschist to amphibolite facies metasediments intruded by large pre- to syn-tectonic batholiths of leucogranites and an association of monzonite, granodiorite and biotite granite forming a late tectonic high-K calc-alkaline suite. U-Pb zircon dating yields ages of 635 ± 3 Ma and 613 ± 8 Ma on a peraluminous biotite-leucogranite (containing numerous inherited Archean and Paleoproterozoic zircon cores) and a muscovite-leucogranite, respectively. Geochemical fingerprints are very similar to some evolved Himalayan leucogranites suggesting their parental magmas were formed after muscovite and biotite dehydration melting of metasedimentary rocks. A biotite-granite sample belonging to the late tectonic high-K to shoshonitic suite contains zircon rims that yield an age of 540 ± 5 Ma with concordant inherited cores crystallized around 1050 Ma. Given the high-Mg# (59) andesitic composition of the intermediate pyroxene-monzonite, the very similar trace-element signature between the different rock types and the unradiogenic isotopic signature for Nd, the late-kinematic high-K to shoshonitic rocks formed after melting of the enriched mantle and further differentiation in the crust. These data indicate that the southern Ouaddaï was part of the Pan-African belt. It is proposed that it represents a continental back-arc basin characterized by a high-geothermal gradient during Early Ediacaran leading to anatexis of middle to lower crustal levels. After tectonic inversion during the main Pan-African phase, late kinematic high-K to shoshonitic plutons emplaced during the final post-collisional stage.

scholarly journals Petrology and mineral chemistry of peraluminous Marziyan granites, Sanandaj-Sirjan metamorphic belt (NW Iran)

2015 ◽  
Vol 66 (5) ◽  
pp. 361-374 ◽  
Author(s):  
Esmaiel Darvishi ◽  
Mahmoud Khalili ◽  
Roy Beavers ◽  
Mohammad Sayari
Keyword(s):  
Mineral Chemistry ◽  
White Mica ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Metamorphic Belt ◽  
Nw Iran ◽  
The North ◽  
Continental Plate ◽  
High K ◽  
Type Granite

AbstractThe Marziyan granites are located in the north of Azna and crop out in the Sanandaj-Sirjan metamorphic belt. These rocks contain minerals such as quartz, K-feldspars, plagioclase, biotite, muscovite, garnet, tourmaline and minor sillimanite. The mineral chemistry of biotite indicates Fe-rich (siderophyllite), low TiO2, high Al2O3, and low MgO nature, suggesting considerable Al concentration in the source magma. These biotites crystallized from peraluminous S-type granite magma belonging to the ilmenite series. The white mica is rich in alumina and has muscovite composition. The peraluminous nature of these rocks is manifested by their remarkably high SiO2, Al2O3and high molar A/CNK (> 1.1) ratio. The latter feature is reflected by the presence of garnet and muscovite. All field observations, petrography, mineral chemistry and petrology evidence indicate a peraluminous, S-type nature of the Marziyan granitic rocks that formed by partial melting of metapelite rocks in the mid to upper crust possibly under vapour-absent conditions. These rocks display geochemical characteristics that span the medium to high-K and calc-alkaline nature and profound chemical features typical of syn-collisional magmatism during collision of the Afro-Arabian continental plate and the Central Iranian microplate.

scholarly journals Petrology and mineralogy of the Ulaan Del Zr-Nb-REE deposit, Lake Zone, Western Mongolia

2020 ◽  
Vol 50 ◽  
pp. 45-62
Author(s):  
Sanjsuren Oyunbat
Keyword(s):  
Fine Grained ◽  
Late Cambrian ◽  
Hydrothermal Processes ◽  
Western Mongolia ◽  
Lake Zone ◽  
High K ◽  
Ore Minerals ◽  
Type Granite ◽  
Host Rocks ◽  
Syenite Porphyry

The Ulaan Del deposit is located in the Lake Zone, Western Mongolia. In the area, middle-late Devonian alkali dykes of the Khalzan Complex are hosted in the middle-late Cambrian granodiorite-tonalite of the Togthohiinshil Complex. The alkali dykes of the Khalzan complex comprise medium- to fine-grained syenite, microsyenite, syenite-porphyry and trachyte, trachyrhyolite, and trachyandesite. The dykes are replaced to silica, sericite, albite, fluorite and are brecciated. They crosscut by quartz and quartz-carbonate veinlets. The dykes contain zircon (>0.19% Zr) with a total of rare earth elements oxides >0.1%. The host rocks of the Togtokhiinshil complex are mid-K, metaluminous, I- type granite, depleted in HFSE. Based on geochemical and mineralogical data, economic REE mineralization is concentrated in syenite and syenite porphyry of calc-alkaline high K to shoshonite series of A- type granite, emplaced at within a plate setting. Syenite dykes are enriched in REE. Ore minerals are zircon, apatite, sphene, monazite, xenotime, synchysite, parisite, fluorite and REE complex minerals, pyrite, rutile and limonite. Magmatic, metasomatic and hydrothermal processes significantly contributed to the formation of Zr, Nb, REE and Y mineralization at the Ulaan Del deposit.

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