Geochemistry and Petrogenesis of Granitoid
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Indian Journal of Fundamental and Applied Life Sciences ISSN: 2231– 6345 (Online) An Open Access, Online International Journal Available at www.cibtech.org/sp.ed/jls/2014/04/jls.htm 2014 Vol. 4 (S4), pp. 1693-1709/Ardalan et al. Research Article GEOCHEMISTRY AND PETROGENESIS OF GRANITOID PLUTON AND ENCLAVES IN QOHROUD – KASHAN *Afshin Ashja Ardalan1, Mina Khodadadi1, Mohammad Hashem Emami2, Jamal Sheikh Zakariaie 3, Mohammad Hosein Razavi4 and Abdollah Yazdi5 1Department of Geology, Islamic Azad University, North Tehran Branch, Tehran, Iran 2Department of Geology, Islamic Azad University, Islamshahr Branch, Islamshahr, Iran 3Department of Geology, Islamic Azad University, Science and Research Branch, Tehran, Iran 4Department of Geology, Kharazmi University, Tehran, Iran 5Department of Geology, Islamic Azad University, Kahnooj Branch, Kerman, Iran *Author for Correspondence ABSTRACT The area is located in northwest of Isfahan, 30 kilometers south of Kashan District, and southern section of Qamsar. The longitude of the area of study is 51º, 19′, 13″, E to 51º, 26′, 26″, E and its latitude is 33º, 34′, 24″ N to 33º, 44′, 24″ N. The rocks of the Qohrud batholithic mass and its enclaves are more quartz monzonite. The rocks are peraluminous that are rich of alomin. These rocks are classified in magmatic series of subalkaline, and belong to calcalkaline magmatic series subdivision. According to origin classification, they are considered I type, S- type and A- type. Tectonically are both in the position of volcanic arc granite (VAG) that is related to continental arc granite (CAG) and within plate granite (WPG) that is related to continental rifting in back arc basin. The rocks of the Qohroud area originate from continental crust arc that mixing with back arc basin rifting magmas and hybrid magma stop in the upper crust and balanced. Keywords: Kashan, Qohroud, Granitoid, Petrogenesis INTRODUCTION The igneous rocks of this area are themselves part of the Urumieh - Dokhtar or Sahand - Bazman volcanic belt. The area which is being studied is located in northwest of Isfahan Province, 30 kilometers south of Kashan, and south of the Qamsar county. This area is adjacent to Qaza’an, Qohroud, and Jevinan parishes (Figure 1), (Internet, 2013). This area is located at the east side of the 1:100000 geological map of Kashan, in Qohroud mountain range which is illustrated as red granitoid (Zahedi, 1991). MATERIALS AND METHODS 1- Methodology of Research and Processes a- Arriving at the area for collecting (carrying out) the rock samples and the field observation for determining points and documenting ground checkpoints by GPS. b- Selecting a number of samples for XRF and ICP- ms analysis. c- Statistical and calculative computer works and plots and conclusion. RESULTS AND DISCUSSION 3-Discussion 3-1- Geology of the Area The longitude of the area of study is 51º, 19′, 13″, E to 51º, 26′, 26″, E and its latitude is 33º, 34′, 24″ N to 33º, 44′, 24″ N (Figure 2). The collected samples that taken from the Qohroud pluton arequartz monzonite, granite, granodiorite, quartzmonzodiorite. But mostly is quartz monzonite. Also, number of enclaves can be seen that are generally quartz monzonite. © Copyright 2014 | Centre for Info Bio Technology (CIBTech) 1693 Indian Journal of Fundamental and Applied Life Sciences ISSN: 2231– 6345 (Online) An Open Access, Online International Journal Available at www.cibtech.org/sp.ed/jls/2014/04/jls.htm 2014 Vol. 4 (S4), pp. 1693-1709/Ardalan et al. Research Article Figure 1: Geographical location of the area with 1:2500000 scale (Internet, 2013) Figure 2-a: Geological map of the area with 1:100000 scale and more magnification (Zahedi, 1991) © Copyright 2014 | Centre for Info Bio Technology (CIBTech) 1694 Indian Journal of Fundamental and Applied Life Sciences ISSN: 2231– 6345 (Online) An Open Access, Online International Journal Available at www.cibtech.org/sp.ed/jls/2014/04/jls.htm 2014 Vol. 4 (S4), pp. 1693-1709/Ardalan et al. Research Article Figure 2b: Legend of Geological map of the area with 1:100000 scale (Zahedi, 1991) 3-2- Geochemistry and Petrogenesis of the Rocks of the Area Using the Chemical Analysis Data Granitoid Samples were analyzed for content of major and trace elements by XRF and ICP-MS method, (Iranian Organization for Geology and Quarry Expedition, 2012), They are presented in table (1,2,3). Also 4 enclave samples are presented similar. The granitoids are characterized by 58.6 – 70.9 % SiO2 that aregeochemically acidic and intermediate. The enclaves show a compositional range from 55.6 _ 58.9% SiO2.Also the rocks show a compositional range from 0.58 _ 1.68%LOI that are mostly less than 1. The granitoids are characterized by 1.5 – 3.1 % K2O,3.2 – 7.2 % CaO,1.9– 3% Na2O,1– 4% MgO, 2.9 – 11.5 % Fe2O3tand 13.4 – 18.1 % Al2O3. Todiscrimination different rock groups of the area and naming, using the chemical analysis data and norms, there is different diagrams are used. One of such plots is (Debon and Le-Fort, 1983) in (Figure 3). In this plot, samples are mostly positioned in adamelite (quartz monzonite) distinct. These rocks are classified in magmatic series of subalkaline, and belong to calcalkaline magmatic series (Figures 4,5,6,), (Irvine and Baragar, 1971), (Hastie et al., 2007). Also figure (6) show Co- Th plot of Classification for magmatic series, that show high- k calc- alkaline and shoshonite series for Qohroud samples (Hastie et al., 2007). The rocks are peraluminous that are rich of alumin (Al2O3) (Figure 7) (Villaseca et al., 1998). According to origin classification, they are considered I- type, S- type and A- type. Some of the samples are on the border of distinct (Figure 8), (Whalen et al., 1987). Trace element compositions of granitic rocksare potentially applied for discrimination of their tectonic settings (Pearce et al., 1984; Harris et al., 1986). For the purpose of discrimination of a possible tectonic setting of the area, characterization of the granitic rocks is of particular importance. On the Y-Nb and Rb- (Y+Nb) diagrams (Figure 9), Tectonically are located both in the area of volcanic arc granite (VAG) that is continental arc granite (CAG) and within plate (WPG) that is continental rifting in back arc basin (Figure 9,10), (Harris et al., 1986). To help understand the origin and tectonic setting for these A- type granites, we show them on discrimination diagrams such as (Figure 11). The diagram use trace- element ratios to distinguish between sources for two distinct A-type compositions, A1 and A2. A1-type granitoids (Y/ Nb < 1.2) were generated in hotspots, plumes, or continental rift zones. A2-type granitoids (Y/ Nb > 1.2) are associated with post collisional settings (Eby, 1992). © Copyright 2014 | Centre for Info Bio Technology (CIBTech) 1695 Indian Journal of Fundamental and Applied Life Sciences ISSN: 2231– 6345 (Online) An Open Access, Online International Journal Available at www.cibtech.org/sp.ed/jls/2014/04/jls.htm 2014 Vol. 4 (S4), pp. 1693-1709/Ardalan et al. Research Article Table 1: Major elements analytical data for the rocks of the area, by XRF, (Iranian Organization for Geology and Quarry Expedition, 2012) Sample SiO2 Al2O3 MgO K2O TiO2 MnO Cao number Na2O M1 60.7 17.2 2.4 2 0.7 0.1 2.5 5.9 M12 63.7 16 2.1 2.5 0.6 0.2 2.2 5 M13 59.9 17.6 2.7 1.6 0.7 0.1 2.6 6.3 M16 57.9 18 2.7 1.9 0.8 0.2 2.7 6.6 M23 63.2 16.5 2.2 2.3 0.7 0.2 2.8 5 M29 58.9 17.4 2.6 1.8 0.8 0.2 3 5.8 M35 68.5 15.5 1.4 2.4 0.4 0.1 2.7 3.9 M46 55.6 17.9 3.5 1.8 0.7 0.3 3 7.2 M52 66.8 16.1 1.7 3.1 0.5 0.01 2.6 3.9 M57 65.5 16.4 2 2.8 0.5 0.01 2.7 4.2 M65 66.1 16 2.1 2.9 0.5 0.01 2.6 4.1 M71 56.9 18 3.3 2.3 0.8 0.2 2.9 6.2 M77 63.9 16.3 2.2 2.3 0.7 0.1 2.5 4.9 M84 58.6 13.4 4 2.3 1.1 0.2 1.9 5.3 M90 65.4 16 2.1 3 0.6 0.1 2.6 4.3 M97 65.6 15.8 1.9 2.3 0.6 0.1 2.5 4.6 M99 66.3 15.9 1.9 2.8 0.6 0.01 2.7 4.1 M103 62.7 16.9 2.1 1.9 0.7 0.1 2.6 5.4 M119 59 18.1 3.2 1.5 0.6 0.1 2.4 6.8 M33 70.9 15.3 1 2.7 0.3 0.01 2.8 3.2 Sample P2O5 BaO So3 LOI Fe 2O3t FeO FeOt number M1 0.2 0.01 0.01 1.16 7 4.8 5.3 M12 0.2 0.01 0.01 1.68 5.9 3.8 4.2 M13 0.2 0.01 0.01 0.83 7.2 5 5.5 M16 0.3 0.01 0.01 0.72 8 5.7 6.3 M23 0.2 0.01 0.01 0.86 5.9 3.7 4.11 M29 0.2 0.01 0.01 1.01 8.1 5.8 6.4 M35 0.2 0.01 0.01 0.62 4.1 2.2 2.4 M46 0.4 0.01 0.01 0.87 8.6 6.4 7.11 M52 0.2 0.01 0.01 0.79 3.9 1.9 2.11 M57 0.3 0.01 0.01 1.05 4.3 2.3 2.5 M65 0.2 0.01 0.01 0.89 4.3 2.3 2.5 M71 0.3 0.2 0.1 1.3 7.4 5.1 5.6 M77 0.2 0.01 0.01 0.77 5.8 3.6 4 M84 0.4 0.01 0.01 0.93 11.5 8.9 9.8 M90 0.2 0.01 0.01 0.61 4.8 2.7 3 M97 0.2 0.01 0.01 0.68 5.3 3.2 3.5 M99 0.2 0.01 0.01 0.72 4.4 2.3 2.5 M103 0.3 0.01 0.01 0.63 6.4 4.2 4.6 M119 0.3 0.01 0.01 1.25 6.6 4.5 5 M33 0.1 0.01 0.01 0.58 2.9 1.1 1.2 The characterization of these A-type samples indicates that these rocks may represent partially melted extensional crust in back arc basin that is relation to rifting.