Geochemistry of Mesoproterozoic sedimentary rocks of upper Vindhyan Group, southeastern Rajasthan and implications for weathering history, composition and tectonic setting of continental crust in the northern part of Indian shield
“…Ages displayed for the ANS are from Allen (2007) and Johnson et al (2011); ages displayed for Oman are from Allen (2007), Rantakokko et al (2014) and this study. Ages displayed for Rajasthan are compiled from the following studies: Haldar & Deb (2001); Buick et al (2006); Gregory et al (2009); Van Lente et al (2009); Just et al (2011); Cozzi, Rea & Craig (2012); Raza et al (2012); Ashwal et al (2013); Davis, Meert & Pandit (2014). Figure 17.Geological outcrop map of the ANS, Oman and India in Gondwana adapted from Collins and Pisarevsky (2005).…”
Section: Discussionmentioning
confidence: 99%
“…Granitoids have been dated from Rajasthan and from Nagar Parkar in eastern Sind (Pakistan) at c . 1100 Ma (Raza et al 2012; Meert, Pandit & Kamenov, 2013). However, no evidence of pre-existing crust occurs west of the Western Margin Fault of the Aravalli–Delhi Orogen.…”
The Omani basement is located spatially distant from the dominantly juvenile Arabian–Nubian Shield (ANS) to its west, and its relationship to the amalgamation of those arc terranes has yet to be properly constrained. The Jebel Ja'alan (NE Oman) basement inlier provides an excellent opportunity to better understand the Neoproterozoic tectonic geography of Oman and its relationship to the ANS. To understand the origin of this basement inlier, we present new radiogenic isotopic data from igneous bodies in Jebel Ja'alan. U–Pb and 40Ar/39Ar geochronological data are used to constrain the timing of magmatism and metamorphism in the jebel. Positive εHf and εNd values indicate a juvenile origin for the igneous lithologies. Phase equilibria modelling is used to constrain the metamorphic conditions recorded by basement. Pressure–temperature (P–T) pseudosections show that basement schists followed a clockwise P–T path, reaching peak metamorphic conditions of c. 650–700°C at 4–7.5 kbar, corresponding to a thermal gradient of c. 90–160°C/kbar. From the calculated thermal gradient, in conjunction with collected trace-element data, we interpret that the Jebel Ja'alan basement formed in an arc environment. Geochronological data indicate that this juvenile arc formed during Tonian time and is older than basement further west in Oman. We argue that the difference in timing is related to westwards arc accretion and migration, which implies that the Omani basement represents its own tectonic domain separate to the ANS and may be the leading edge of the Neoproterozoic accretionary margin of India.
“…Ages displayed for the ANS are from Allen (2007) and Johnson et al (2011); ages displayed for Oman are from Allen (2007), Rantakokko et al (2014) and this study. Ages displayed for Rajasthan are compiled from the following studies: Haldar & Deb (2001); Buick et al (2006); Gregory et al (2009); Van Lente et al (2009); Just et al (2011); Cozzi, Rea & Craig (2012); Raza et al (2012); Ashwal et al (2013); Davis, Meert & Pandit (2014). Figure 17.Geological outcrop map of the ANS, Oman and India in Gondwana adapted from Collins and Pisarevsky (2005).…”
Section: Discussionmentioning
confidence: 99%
“…Granitoids have been dated from Rajasthan and from Nagar Parkar in eastern Sind (Pakistan) at c . 1100 Ma (Raza et al 2012; Meert, Pandit & Kamenov, 2013). However, no evidence of pre-existing crust occurs west of the Western Margin Fault of the Aravalli–Delhi Orogen.…”
The Omani basement is located spatially distant from the dominantly juvenile Arabian–Nubian Shield (ANS) to its west, and its relationship to the amalgamation of those arc terranes has yet to be properly constrained. The Jebel Ja'alan (NE Oman) basement inlier provides an excellent opportunity to better understand the Neoproterozoic tectonic geography of Oman and its relationship to the ANS. To understand the origin of this basement inlier, we present new radiogenic isotopic data from igneous bodies in Jebel Ja'alan. U–Pb and 40Ar/39Ar geochronological data are used to constrain the timing of magmatism and metamorphism in the jebel. Positive εHf and εNd values indicate a juvenile origin for the igneous lithologies. Phase equilibria modelling is used to constrain the metamorphic conditions recorded by basement. Pressure–temperature (P–T) pseudosections show that basement schists followed a clockwise P–T path, reaching peak metamorphic conditions of c. 650–700°C at 4–7.5 kbar, corresponding to a thermal gradient of c. 90–160°C/kbar. From the calculated thermal gradient, in conjunction with collected trace-element data, we interpret that the Jebel Ja'alan basement formed in an arc environment. Geochronological data indicate that this juvenile arc formed during Tonian time and is older than basement further west in Oman. We argue that the difference in timing is related to westwards arc accretion and migration, which implies that the Omani basement represents its own tectonic domain separate to the ANS and may be the leading edge of the Neoproterozoic accretionary margin of India.
“…A similar approach in sedimentary basin studies provided information about weathering history, composition, and tectonic setting of the continental crust (Roser and Korsch, 1986;Raza et al, 2012).…”
Section: Accepted Manuscriptmentioning
confidence: 99%
“…In suspended sediments of large rivers, the Na weathering index is always greater than unity indicating that suspended sediments are depleted with respect to UCC, whereas the weathering indices of Ca and Mg usually exhibit values less than one, reflecting the presence of carbonate in the suspended sediment. Following the methodologies used in studies of sedimentary basins (Roser and Korsch, 1986;Rawlins et al, 2003;Raza et al, 2012), we have used Na as a normalizing element to study the intensity of weathering processes in relation to the provenance of parent materials for soils formed from the lithologies of the UCC (Fig. 8).…”
“…Generally, it was shown that MgO ≥ CaO, suggesting the presence of mafic minerals (Table 4). Fe 2 O 3 content ranges from 2.49 to 5.22 wt.% and suggests that Fe 2 O 3 is not only contained by minerals, such as hornblende, biotite and pyroxenes, but also distributed in opaque minerals present in these rocks (Naqvi 1978;Ghazi and Mountney 2011;Ghabeishavi et al 2010;Raza et al 2010Raza et al , 2012aMoosavirad et al 2012). Iron forms the magnetite and ilmenite minerals in combination with Fe 2 O3 and TiO 2 .…”
The Early Eocene sequence of Neyshaboor, Binalud region of Iran is predominantly composed of arenaceous deposits. Two stratigraphically important sections from the Damanjan and Taghan areas have been investigated based on field work, petrographic and geochemical analyses. Eight lithofacies were identified and have been grouped in to conglomerate, sandstone, and mudstone facies association. Petrographic and geochemical data show that the Early Eocene sandstones are mainly composed of arkoses and litharenites classes. Provenance analysis indicates that sediments were supplied from a nearby andesitic-granitic source with minor contribution of metamorphic and sedimentary sources. The presence of predominance of monocrystalline over polycrystalline quartz and abundance of K-feldspars; Cu and Pb contents also support this interpretation. However, subordinate representation of polycrystalline quartz grains, chert, volcanic rock fragments, biotite, zircon, as well as higher percentage of MgO and Fe 2 O 3 , suggest some contribution from high-grade metamorphic gneissic rocks and, to a lesser degree, from intermediate to basic volcanics. Climate varied from humid in the beginning of the sedimentation to sub-humid and arid during the later phases. Sedimentation was also influenced by prominent tectonic activity in the source when coarser clastic sediments were deposited as multistoried conglomerates. Lithofacies characters of the rock succession suggest sedimentation took place in a piedmont fan environment, adjacent to a rising orogeny in an active foreland basin setting. Clay to sand and gravel-sized Highlights Early Eocene arenaceous sequences of Binalood region of Iran are studied using Lithofacies Analysis, Petrography and geochemistry. Objectives were to interpret palaeoenvironment and provenance as well as to know the tectonics of the source area and basin. Also, to know the effect of climate on the mode of sedimentation. Deposition took place under piedmont fan environment in an active foreland basin setting. Clay to sand and gravel sized sediments were laid down by meandering and braided rivers and also as debris flows. Climate changed from humid in the beginning to sub-humid and arid during the later phases of sedimentation. Source rocks were mainly andesitic-granitic type as substantiated by petrography and geochemical analysis.A. Jafarian sediments were laid down by meandering and braided rivers and by debris flows under changing conditions of climate and tectonics.
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