U–Th–Pb monazite geochronometry of the Eastern Ghats Belt, India: Timing and spatial disposition of poly-metamorphism

Simmat, Ralf; Raith, M.

doi:10.1016/j.precamres.2007.07.016

Cited by 162 publications

(144 citation statements)

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“…They favour a model of a single granulite facies metamorphic event. However, the large database generated by Simmat and Raith (2008) on chemical dating of monazites in samples collected throughout the EGB indicates a complex polycyclic evolution of the EGB. Older electron microprobe spot ages of monazite are obtained from small grains armoured in porphyroblastic garnets or in the interiors of such grains and also in the cores of the grains in the matrix.…”

Section: Discussionmentioning

confidence: 99%

New constraints on the metamorphic evolution of the Eastern Ghats Belt, India, based on relict composite inclusions in garnet from ultrahigh‐temperature sapphirine granulites

Rao

Chmielowski

2011

Geological Journal

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The sapphirine granulites from Gangaraju Madugula, Eastern Ghats Belt (EGB), India preserve a rich variety of mineral assemblages and unique isolated and composite mineral inclusions within garnet that provide robust evidence for extreme crustal metamorphism at ultrahigh temperature (UHT) conditions (>9008C). Diagnostic UHT assemblages in these rocks include sapphirine þ quartz, spinel þ quartz and high alumina orthopyroxene þ sillimanite þ quartz. The stability of spinel þ quartz, sapphirine þ quartz and orthopyroxene þ sillimanite þ quartz assemblages provides evidence for temperatures exceeding 9608C at moderate pressures. The mineral association of garnet-orthopyroxene is indicative of a subsequent high P-UHT metamorphic event as indicated by the high alumina contents of orthopyroxene (>10 wt% Al 2 O 3 ) coexisting with garnet. Peak P-T conditions of $9708C and 9.5 kbars are calculated from conventional garnet-orthopyroxene geothermobarometry. Calculated isochemical sections constructed in the model system Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O-TiO 2 -Fe 2 O 3 (NCKFMASHTO) for the sapphirine granulites and garnet-orthopyroxene granulites adequately predict phase relationships that are consistent with those observed in the rocks. An evaluation of the assemblages and textures and P-T estimates indicate a three-stage evolution of the sapphirine granulites and associated garnet-orthopyroxene granulites: (1) inclusion assemblages with sapphirine, spinel and quartz on the low-pressure prograde path (M 1 stage); (2) a peak UHT assemblage of porphyroblastic garnet-orthopyroxene (M 2 stage) and (3) a retrogression that resulted in orthopyroxene-cordierite intergrowths and biotite rims on Grt (M 3 stage). The sapphirine granulites and associated garnet-orthopyroxene granulites indicate that they grew during the prograde and retrograde stage. The thermo-barometric estimates from mineral compositions and the complimentary isochemical sections approached from bulk rock compositions allow tighter constraints to be placed on the P-T evolution of this sector of the EGB.

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Section: Discussionmentioning

confidence: 99%

New constraints on the metamorphic evolution of the Eastern Ghats Belt, India, based on relict composite inclusions in garnet from ultrahigh‐temperature sapphirine granulites

Rao

Chmielowski

2011

Geological Journal

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“…The metasedimentary granulites are thought as the oldest component and intruded by magmatic rocks, enderbites and charnockites [10,17]. It is important to note that coarse-grained pegmatitic charnockites are commonly recognized as distinct from the large-scale charnockitic bodies and an intrusive relation f this pegmatitic variety into khondalites was reported o by Subba Rao and Divakara Rao [24].…”

Section: Geochronologymentioning

confidence: 90%

“…Although, there is still some debate for the timing of this high temperature event, Mukhopadhyay and Basak [18] argued that the early UHT metamorphic event affected the entire EGP; these authors also noted that the absence of UHT assemblage in some locales may be due to the absence of suitable bulk composition. Simmat and Raith [17] also noted that the earliest and ultra-high temperature granulite metamorphism is recorded from both pelitic and charnockitic assemblages.…”

Section: Geological Backgroundmentioning

confidence: 96%

“…Despite such divergent interpretations, high to ultrahigh temperatures (≥950˚C) and dehydration melting in different crustal protoliths are commonly associated with the first or earliest granulite facies metamorphism in the Eastern Ghats Province [17,18]. The high to ultra-high temperature records and the P-T-t paths reported from the Eastern Ghats Belt are summarized in Figure 2.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…In terms of field relation between two major gneiss components, several workers have argued that khondalites or the sedimentary granulites are the oldest components (supposed xenoliths), and multiply intruded by magmatic rocks, including enderbites and charnockites [10,17]. However, the question of the basement to these sediments remains illusive.…”

Section: Field Relation and Fabric Developmentmentioning

confidence: 99%

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Relative Chronology in High-Grade Crystalline Terrain of the Eastern Ghats, India: New Insights

Bhattacharya

Kar²,

Saw

et al. 2011

IJG

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The two major lithology or gneiss components in the polycyclic granulite terrain of the Eastern Ghats, India, are the supracrustal rocks, commonly described as khondalites, and the charnockite-gneiss. Northern Eastern Ghats belt, north of the Godavari rift has been defined as the Eastern Ghats Province, while that to the south has been defined as the Ongole domain; and although, these distinct crustal domains also record different ages of granulite metamorphism, both of these domains are dominated by the two lithologies. Many of the workers considered the khondalites as the oldest component with unknown basement and the charnockiteprotoliths as intrusive into the khondalites. However, published geochronological data do not corroborate the aforesaid relations. Onset of khondalite sedimentation in the Proterozoic Eastern Ghats Province, constrained by detrital zircon data, as around 1.3 Ga and the charnockite-protolith emplacement between 1.9 and 2.9 Ga, argue against intrusion of felsic magma (tonalite, now enderbite!) in to the khondalites. The field relations of the hornblende-mafic granulite with the two gneiss components together with Sm-Nd isotopic data of the hornblende-mafic granulites (both the xenoliths within charnockites and those interbanded with the khondalites) indicate that khondalite sediments were deposited on older mafic crustal rocks. Mafic basement and supracrustal rocks were subsequently deformed and metamorphosed together during collisional orogeny at high to ultra-high temperatures-partial melting of mafic rocks producing the charnockitic melt; and partial melting of pelitic sediments producing the peraluminous granitoids. This is compatible with all the geochronological data as well as the petrogenetic model of partial melting for the charnockitic rocks in the Eastern Ghats Belt. The Ongole domain, south of the Godavari rift, though, is distinct in terms of the age of first/ earliest UHT metamorphism, but here too the charnockite-protoliths are older mafic rocks evidently not intrusive in to the khondalites..

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Reworking of a basement–cover interface during Terrane Boundary shearing

Bhadra¹,

Gupta²

2015

Ductile Shear Zones

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U–Th–Pb monazite geochronometry of the Eastern Ghats Belt, India: Timing and spatial disposition of poly-metamorphism

Cited by 162 publications

References 58 publications

New constraints on the metamorphic evolution of the Eastern Ghats Belt, India, based on relict composite inclusions in garnet from ultrahigh‐temperature sapphirine granulites

New constraints on the metamorphic evolution of the Eastern Ghats Belt, India, based on relict composite inclusions in garnet from ultrahigh‐temperature sapphirine granulites

Relative Chronology in High-Grade Crystalline Terrain of the Eastern Ghats, India: New Insights

Reworking of a basement–cover interface during Terrane Boundary shearing

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