Geochemical features of granitic rocks using x-ray spectral fluorescence in the Miass region, Southern Ural

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Introduction Different deposits and mineralization were discovered associated with granite intrusions, such as gold deposits, tin, tungsten and several deposits of rare earth elements [1; 2]. Type, origin, and petrogenesis of granite is significant key in formation of specific deposits. Some studies revealed that, various of rare earth elements deposits related to highly fractionated granite intrusions. Also, the Syrostan massive in the southern Ural linked with many deposits such as gold, rare earth elements, and skarn deposits. Therefore, determine the type of granite, identification the magma evolution process, and the geochemistry of granite could lead to a potential ore deposit. Although, several research were conducted in the Syrostan massive and intrusions in southern Ural looking for potential mineralization [2-6]; however, the massive area was not covered with the investigation of the petrogenesis and the geochemistry and conducted them to the mineralization. The aim of this study is to identify geochemical characteristic and type of the granite in order to connect them with type of mineralization and use the result for future researches. Geology of the study area. The Syrostan massive locates in the southwest of the Miass city, southern Ural in the zone of the main Ural deep fault. The massive is among metabasites, shales of several composition and fragment of metamorphosed oceanic crust and the crust of passive margin of the Ural paleocean. The massive is formed in the lower carbonian and has three phases: the first is granodiorite and quartz diorite, the second is double feldspar and plagiogranite, and the third is vein complex [6-8]. The location of the study area almost 15 km northwest of the Miass city (Figure 1). The area of the massive consists of metamorphic complex and marble body lies in the form of lenses crossed by several granite veins and the marble mainly in contact with diorite. The magmatic complex includes quartz diorite, granodiorite, biotite granite, and leucogranite [6; 9; 10]. After intensive of petrographic investigation, nine samples have been selected for major oxides analysis. Изображение выглядит как карта Автоматически созданное описание Figure 1. The Syrostan granite massive's modified geological map, which includes the Dark Kingdom of Marble Deposit: 1 - gneiss; 2 - mica quartz schist; 3 - marble limestone; 4 - quartzite; 5 - shale; 6 - marble; 7 - carbonaceous shale; 8 - quaternary sediments; 9 - granodiorite, quartz diorite, diorite; 10 - porphyric biotite granites; 11 - pink porphyric biotite granites; 12 - veined granite and plagiogranite; 13 - pegmatites; 14 - serpentinites; 15 - tectonic faults; 16 - occurrence of niobium 1. Analytical methods Determination of the concentration of major oxides in the samples was executed by x-ray spectral fluorescence analysis (XRF) on a sequential vacuum spectrometer (with wavelength dispersion), model Axios mAX manufactured by PAN alytical (Netherlands). The analysis was performed at the Center for Collective Use of the IGEM RAS (Moscow, Russia). 2. Results and discussion 2.1. Petrography and mineral compositions Microgranite is composed primarily of quartz (15-25%), microcline (20-50%), plagioclase (20-40%), and biotite (5-10%) and has a medium to coarse grained texture (Figure 2, a). Recrystallized quartz has two generations. This indicates that there has been deformation. Sericite and muscovite are discovered after plagioclase. Plagioclase exhibits sericitization and epidotization as a result of hydrothermal activity [11; 12]. Plagioclase zoning shows epidote and sericite from core to rim (Figure 2, b). Furthermore, chlorite, epidote, and calcite are secondary minerals. Accessory minerals include opaque minerals such as zircon and apatite. Изображение выглядит как грибок, лишайник Автоматически созданное описание a b Figure 2. A microscopic examination of granitic and diorite rocks: a - granitic rocks with quartz, plagioclase, and biotite (analyzer out); b - plagioclase grain partially mixed with a sericite aggregate (analyzer in) 2.2. Geochemical properties and granitic rocks types Table 1 shows the major oxides and geochemical compositions of granitoids rocks. Classification of granitoids rocks using TAS diagram [13] shows that most rocks are granite and one sample is syeno-diorite (Figure 3, a), similarly the classification based on Middlemost diagram [14], total alkali vs. silica demonstrate the rocks as granite, monzodiorite, and monzonite (Figure 3, b). The investigated granite samples have a high SiO2 contents ranging from 76.15 to 59.55 wt.%. Diorite shows and silica content about (52.9 wt.%). Granite samples have high total alkalis K2O + Na2O ranging between (7-10 wt.%), moderate K2O/Na2O ratios ranging from 0.35 to 0.85, and low to intermediate CaO (0.5 to 6 wt.%), that followed by low content of P2O5 (0.01 to 0.5%). The LOI (loss on ignition) values ranging from 0.6 to 2 wt.% which is reflect low value. On the K2O with SiO2 dia- gram [15], the investigated samples fall into the high-K calc-alkaline series to slightly calc alkaline series (Figure 3, c). Similarly, the AFM diagram (A = K2O + Na2O, F = FeOt, and M = MgO) [16], demonstrates the evolution of magma form tholeiite into calc alkaline series (Figure 3, d). Al saturation index A/CNK molar (Al2O3/ CaO + Na2O + K2O) vs. A/NK molar (Al2O3/ Na2O + K2O) diagram is plotted and shows the samples plot within the metaluminous field to slightly peraluminous (Figure 3, e) based on the SiO2 vs. FeOt/(FeOt + MgO) diagram (Figure 3, f), determine the samples are magnesian. Both diagrams indicate the type of granite as I-type granite which is related to igneous origin and absence of involving of sedimentary materials. The result of CIPW norm present in Table 2, norm of granite shows quartz ranging from 5 to 30 wt.%, that indicates the granite standard. The investigated samples have a high albite with values ranging from 37.5 to 50.5 wt.%, and mode- rate orthoclase content, with values ranging between, 14.5 to 21.5 wt.%. The norm of corundum in most sample shows 0 value and the rest of samples shows values less than 1 in the average of 0.5 wt.%. These result implying, I-type granite [17; 18]. Using the normative result with more than 10% of Quartz, Ab-An-Or diagram has been plotted (Figure 4, a). the diagram shows the trondhjemite as dominant plutonic rock type, granite and tonalite represent the rest of the samples. Table 1 Compositions of whole rock major oxides in granitoid rocks Major oxides, wt.% Samples MG1 MG2 MG3 LG1 LG2 LG3 BG1 BG3 D1 SiO2 70.64 70.45 69.85 73.43 76.17 74.62 69.52 59.54 52.89 Al2O3 14.62 15.17 14.82 12.71 12.89 13.84 15.38 17.3 17.95 Na2O 5.29 4.89 4.94 5.98 5.84 5.63 4.42 5.33 5.34 MgO 0.53 0.46 0.75 0.19 0.1 0.08 0.82 1.65 3.95 K2O 3.47 3.43 3.45 2.44 2.47 3.61 3.67 3.5 2 CaO 2.06 1.81 1.99 2.77 0.95 0.53 2.23 4.81 6.37 TiO2 0.23 0.22 0.21 0.02 0.03 0.02 0.39 0.66 1.18 MnO 0.043 0.037 0.038 0.015 0.022 0.007 0.033 0.093 0.096 Fe2O3 1.93 1.82 1.98 0.28 0.52 0.36 2.51 5.02 7.61 P2O5 0.09 0.07 0.07 0.01 0.02 0.02 0.14 0.28 0.53 LOI 0.81 1.19 1.58 2.13 0.83 1.13 0.64 1.34 1.08 SUM 99.71 99.55 99.68 99.98 99.84 99.85 99.75 99.52 98.99 A/NK 1.17 1.29 1.25 1.02 1.05 1.05 1.37 1.38 1.64 A/CNK 0.902 1.01 0.957 0.725 0.92 0.979 1.005 0.812 0.796 K2O/Na2O 0.655 0.701 0.698 0.408 0.422 0.641 0.83 0.656 0.374 Na2O/K2O 1.52 1.43 1.42 2.45 2.36 1.56 1.2 1.52 2.67 Table 2 CIWP norm for investigated samples Mineral, wt.% Samples MG1 MG2 MG3 LG1 LG2 LG3 BG1 BG3 D1 Quartz 22.45 24.5 23.05 25.95 31.25 27.01 24.15 5.15 0 Corundum 0 0.23 0 0 0 0 0.5 0 0 Orthoclase 20.5 20.3 20.5 14.5 14.5 21.5 21.5 20.6 11.8 Albite 44.7 41.5 41.8 50.5 49.5 47.6 37.4 45.1 45.2 Anorthite 5.8 8.5 8 0.63 1.66 1.83 10.15 12.94 19.10 Diopside 2.4 0 0.59 1.02 0.53 0.43 0 5.57 3.85 Wollastonite 0 0 0 4.89 0.92 0.03 0 0 0 Hypersthene 0.2 1.14 1.594 0 0 0 2.04 1.53 1.67 Olivine 0 0 0 0 0 0 0 0 4.47 Ilmenite 0.09 0.07 0.08 0.03 0.04 0.02 0.071 0.3 0 Hematite 1.9 1.82 1.98 0.28 0.52 0.36 2.51 5.02 7.6 Sphene 0.5 0 0.41 0.008 0.02 0.03 0 1.4 2.89 Rutile 0 0.17 0 0 0 0 0.35 0 0 Apatite 0.2 0.16 0.16 0.02 0.05 0.05 0.33 0.66 1.25 Pyrite 0 0 0 0 0 0 0 0 0.16 Sum 98.9 98.4 98.11 97.85 99.02 98.73 99.13 98.20 98.02 Изображение выглядит как диаграмма Автоматически созданное описание Изображение выглядит как диаграмма Автоматически созданное описание a b Изображение выглядит как диаграмма Автоматически созданное описание Изображение выглядит как диаграмма Автоматически созданное описание c d Изображение выглядит как диаграмма Автоматически созданное описание Изображение выглядит как диаграмма Автоматически созданное описание e f Figure 3. Plots and classification of the Miass granitoid's major oxides: a - total alkali silica of plutonic rocks [13]; b - TAS diagram for granitoid classification [14]; c - SiO2 versus K2O diagram [15], showing the presence of granitoid rocks among the high-K calc-alkaline series; d - AFM diagram with A = (k2O + Na2O), F = FeOt, and M = MgO [16], showing rock samples from the calc-alkaline series with high k2O + Na2O; e - Al saturation index A/CNK molar [Al2O3/(CaO+Na2O+K2O)] versus A/NK molar (Al2O3/(Na2O+K2O)] diagram, indicating metaluminous to peraluminous samples; f - as a result of the SiO2 vs FeOt/(FeOt + MgO) diagram, all of the samples are magnesian Изображение выглядит как диаграмма Автоматически созданное описание Изображение выглядит как диаграмма Автоматически созданное описание a b Изображение выглядит как диаграмма Автоматически созданное описание c Figure 4. Classifying the igneous rocks using the norm and cations: a - normative Ab-An-Or ternary plot and classification of rocks in the study area using Barker's scheme (1979) [20]; b - Na2O-K2O-CaO ternary plot for Southern Ural studied rocks, Barker's (1979) [20], calc-alkaline (CA) and trondjhemitic (TR) differentiation trends are represented by dashed curves; c - the classififcation of plutonic rocks using the parameter R1 & R2 after [19] caculated from millication proportions, R1 = 4Si - 11(Na + K) - 2(Fe + Ti), R2 = (Al + 2Mg + 6Ca) On Na2O-k2O-CaO diagram (Figure 4, b) define a continuous range from tonalite/trondhjemite to granodiorite as the most observable samples. Using the categorization diagram (Figure 4, c) from [19], for plutonic igneous rocks based on their millications or cation proportions, that widely use and more accurate in classification of plutonic rocks. The plotting parameters RI and R2 are used to plot the data on an x-y bivariate graph. R1 is defined as [4Si - 11(Na + K) - 2(Fe + Ti)] and is displayed on the r-axis. Fe stands for total iron. R2 is shown as a plot along the y-axis and has the formula R2 = (Al + 2Mg + 6Ca). The samples define a continuous range from granite to alkali granite, granodiorite, and syenodiorite, with granite being the most common. Conclusion Granite is silica-enriched with SiO2 ranging between (~76.14-59.54 wt.%) however, diorite shows intermediate chemical composition of SiO2 (~52.89 wt.%). The studied samples show high total alkalis K2O + Na2O = (7.34-9.24 wt.%), K2O/Na2O display moderate ratios ranging from (~0.83-0.37). Low CaO (0.53-6.37 wt.%), and P2O5 (0.01-0.53 wt.%) contents. The rocks belong to the high-K calc-alkaline series to slightly calc alkaline series, and they are metaluminous. The results show that the majority of the rock samples are classified as trondhjemite to slightly to- nalite. The samples in the normative Na2O-k2O-CaO have defined a continuous range as the most observ- able samples, ranging from tonalite/trondhjemite to granodiorite. The petrography investigation of this study revealed ore minerals and indications of hydrothermal solution suggesting mineralization process. The massive associated with many deposits and mineralization such as gold, skarn, and rare earth deposits.

About the authors

Mohammed Abdalla Elsharif Ibrahim

RUDN University

Author for correspondence.
Email: mohammedel-sharif7@gmail.com
ORCID iD: 0000-0002-5634-5695
SPIN-code: 8757-5907
Scopus Author ID: 57200327978

PhD student, Department of Mineral Development and Oil & Gas Engineering, Academy of Engineering

6 Miklukho-Maklaya St, Moscow, 117198, Russian Federation

Vladimir N. Kuleshov

Geological Institute of the Russian Academy of Sciences

Email: vnkuleshov@mail.ru
ORCID iD: 0000-0003-4925-5154
SPIN-code: 5867-2758
Scopus Author ID: 8073984000

Doctor of Sciences (Geochemistry), chief researcher

7 Pyzhevskii Pereulok, Moscow, 119017, Russian Federation

Alexander E. Kotelnikov

RUDN University

Email: kotelnikov-ae@rudn.ru
ORCID iD: 0000-0003-0622-8391
SPIN-code: 6280-5070
Scopus Author ID: 57205586833
ResearcherId: O-3821-2019

PhD in Geology, Associate Professor, Head of the Department of Mineral Development and Oil & Gas Engineering, Academy of Engineering

6 Miklukho-Maklaya St, Moscow, 117198, Russian Federation

Alexey F. Georgievskiy

RUDN University

Email: georgievskiy-af@rudn.ru
ORCID iD: 0000-0003-4835-760X
SPIN-code: 1308-9195
Scopus Author ID: 57212305311

Doctor of Sciences (Geological and Mineralogical), Associate Professor of the Department of Mineral Development and Oil & Gas Engineering, Academy of Engineering

6 Miklukho-Maklaya St, Moscow, 117198, Russian Federation

Samia Abdelrahman Ibrahim

University of Khartoum

Email: samiaibrahim125@gmail.com
PhD in Geology, Head of the Department of Geology, Faculty of Science Al-Gama'a Avenue, Khartoum, 11111, Republic of Sudan

References