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

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.

Supplemental Material: New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada

Supplementary Data Files: (1) Sample list and description; (2) GPS positions of samples; (3) Accuracy of major and trace element bulk rock compositions and precision of repeat analyses; (4) Photomicrographs; (5) Clinopyroxene, plagioclase and olivine compositions; (6) SHRIMP U-Pb methods and results; (7) 7. Nb-Zr-Y tectonic discrimination diagram; (8) Ti-Zr-Y tectonic discrimination diagram; (9) Ti-V tectonic discrimination diagram; (10) MgO-FeOtot_Al2O3 tectonic discrimination diagram; (11) AFM diagram; and (12) Th/Nb vs. SiO2 diagram.

Supplemental Material: New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada

Supplementary Data Files: (1) Sample list and description; (2) GPS positions of samples; (3) Accuracy of major and trace element bulk rock compositions and precision of repeat analyses; (4) Photomicrographs; (5) Clinopyroxene, plagioclase and olivine compositions; (6) SHRIMP U-Pb methods and results; (7) 7. Nb-Zr-Y tectonic discrimination diagram; (8) Ti-Zr-Y tectonic discrimination diagram; (9) Ti-V tectonic discrimination diagram; (10) MgO-FeOtot_Al2O3 tectonic discrimination diagram; (11) AFM diagram; and (12) Th/Nb vs. SiO2 diagram.

Supplemental Material: New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada

Supplementary Data Files: (1) Sample list and description; (2) GPS positions of samples; (3) Accuracy of major and trace element bulk rock compositions and precision of repeat analyses; (4) Photomicrographs; (5) Clinopyroxene, plagioclase and olivine compositions; (6) SHRIMP U-Pb methods and results; (7) 7. Nb-Zr-Y tectonic discrimination diagram; (8) Ti-Zr-Y tectonic discrimination diagram; (9) Ti-V tectonic discrimination diagram; (10) MgO-FeOtot_Al2O3 tectonic discrimination diagram; (11) AFM diagram; and (12) Th/Nb vs. SiO2 diagram.

An Automated Method to Generate and Evaluate Geochemical Tectonic Discrimination Diagrams Based on Topological Theory

Discrimination diagrams can be used to distinguish different tectonic settings of igneous rocks. To improve the quality and efficiency of the design of discrimination diagrams, an automatic design and assessment method for discrimination diagrams is proposed based on topology theory. The method is aimed at programming the traditional process of discrimination diagram design, enabling computers to simulate the visual discrimination process. It thus automatically designs tectonic setting discrimination diagrams by investigating all possible combinations of geochemical elements. In the experiment, analyses of 3803 gabbro samples were collected from three tectonic settings, including island arc, ocean island, and mid-oceanic ridge. Using the proposed method, we found thousands of discrimination diagrams with fields overlapping less than 10%. By analyzing these diagrams, the most critical elements (or element ratio pairs) are identified. Based on the result, the feasibility of using gabbroic rocks to discriminate between tectonic settings is illustrated and four representative discrimination diagrams, including the La/Y–Nb/Ba diagram, Nb/Sc–Sc/Ba diagram, Ba/Nb–Ba/Sc diagram, and La/Na2O–Nb/Ba diagram, are recommended for use. This research supports the view that gabbroic rocks can also be used to discriminate between different tectonic settings. The method could also be applied to other rock types.

Geochemistry and geodynamic setting of Paleoproterozoic granites of Lesser Garhwal Himalaya, India

The granite and gneisses rocks are well exposed around Toneta, Tilwara and Chirbatiyakhal region in the Lesser Garhwal Himalaya have less studied which consider as Paleoproterozoic age. The granites from Toneta area are classified as K-rich peraluminous granite with low Na2O varies from 0.85 to 2.4 wt.% and high K2O content varies from 5.0 to 6.9 wt.%. The average Al2O3 (14.16 wt.%) in the granite is greater than the total alkalies (Na2O+K2O = Av. 7.62 wt.%), the Titania (TiO2) content is low ranging from 0.1 to 0.28 wt. %. In the Y + Nb – Rb, Y – Nb, Ta + Yb – Rb, and Yb – Ta discrimination diagram of Pearce et al. (1984) show that the Toneta granites mostly plots within the syn-collision granite fields. This is typical collisional granite.

Geochemical assessment of claystone deposits from the Patti Formation, Southern Bida Basin, Nigeria

Geochemical studies of claystone deposits from the Patti Formation in the southern Bida Basin, north-Central Nigeria, were carried out on representative samples to determine the basin’s depositional conditions, provenance and tectonic setting. The localities within the study area included Gegu, Ahoko, Ahoko-Etigi, Omu and Idu.Semi-quantitative phase analysis using the Rietveld method and X-ray powder diffraction data revealed that the claystone samples had prominent kaolinite with other constituents such as quartz, illite–muscovite, K-feldspar, pyrite, marcasite, anatase, rutile and gorceixite.Enrichment of Al2O3, Ba, Th, Sr, Cr and La suggests that these elements are primarily controlled by the dominant clay minerals.Geochemical parameters such as U, U/Th, Ni/Co, V/Cr and Cu/Zn ratios strongly implied that these claystones were deposited in an oxidising environment. Provenance deducing ratios for felsic, mafic and basic igneous rocks were compared. Al2O3/TiO2 ratio suggested intermediate to felsic rocks as the probable source rocks for the claystone samples; however, Y/Ni, Cr/V, La/Sc and Th/Sc ratios suggested a felsic progenitor. The tectonic discrimination diagram showed that the samples’ plot was within the region specified for passive margin-type tectonic setting.

MINERALOGY AND PETROLOGY OF THE BRNJICA GRANITOIDS (EASTERN SERBIA)

The Variscan Brnjica granitoids in East Serbia, occurring in the Kucaj Terrane of the Carpatho-Balkanides, are composed of hornblende - biotite tonalité (TON), biotite granodiorite (GRD), twomica granite (TMG) and leucogranite (LG). The rocks analyzed are slightly peraluminous. A preplate collision tectonic environment is supported based on the R1-R2 discrimination diagram. A two-step mixing plus fractional crystallization (MFC) process is considered responsible for the evolution of the Brnjica granitoids. In the 1st step, the parental magma (having the composition of the more basic TON) is forming the mineral assemblage Pl596Biio.3Hbio.7Mto.7Titi.oQzi7.7 by 44% crystallization, and at the same time is mixed (r=0.1) with a magma similar to TMG to give a melt similar to the composition of the less evolved GRD. In the 2nd step, 60% crystallization (Pl39oKfi oBÌ25oZr06Api aMti 4Titi 0QZ303) of the less evolved GRD and a simultaneous mixing with the same acid magma (TMG) but with higher r (0.6) is needed for the genesis of GRD group. The TON could originate in the crust by melting of amphibolites and basalts under various P-T conditions while the granites could be crustal melts produced by melting of amphibolites, gneisses, graywackes and pelites. Pressure of 2.3 to 4.1 kb and temperatures from 626 to 813 °C were calculated for TON, using hornblende and co-existing hornblende and plagioclase compositions respectively.