The tectonic evolution of the Ongole Domain, India: A
metamorphic and geochronological approach
Bonnie Joanne Henderson
Centre for Tectonics, Resources and Exploration
School of Earth and Environmental Sciences
The University of Adelaide, South Australia
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Contents ABSTRACT ...... 5
1. INTRODUCTION ...... 5
2. GEOLOGICAL BACKGROUND ...... 7
2.1 The Eastern Ghats Belt ...... 7 2.2 The Krishna Province and Ongole Domain ...... 8 2.3 Metamorphism in the Ongole Domain ...... 10 3. STRUCTURAL SETTING AND FIELD RELATIONSHIPS ...... 11
3.1 Structural and field work overview ...... 11 3.1.2 DOMAIN 1 ...... 11 3.1.3 DOMAIN 2 ...... 12 4. PETROGRAPHY ...... 14
4.1 Pyroxene bearing meta-granites (charnockites) ...... 14 4.2 Garnet-bearing granite...... 15 4.3 Metagranodiorites...... 16 4.4 Metagranites ...... 16 4.5 Quartzofeldspathic gneiss ...... 16 4.6 Garnet bearing meta-sedimentary rocks ...... 17 4.7 Interpreted petrogenesis of the metasedimentary rocks ...... 18 5. METHODOLOGIES ...... 20
5.1 Quantified metamorphic analysis: P-T pseudosections ...... 20 5.2 LA-ICP-MS U-Pb zircon and monazite geochronology ...... 20 5.4 LA-MC-ICP-MS Lu/Hf isotopes ...... 21 6. RESULTS ...... 21
6.1 Mineral chemistry ...... 21 6.1.1 GARNET ...... 21 6.1.2 FELDSPARS ...... 22 6.1.3 CORDIERITE ...... 22 6.1.4 ILMENITE ...... 23 6.1.5 MAGNETITE ...... 23 6.1.6 ORTHOPYROXENE ...... 23 6.1.7 BIOTITE ...... 23 3
7. CALCULATED PHASE DIAGRAM ...... 24
8. ZIRCON DESCRIPTIONS AND RESULTS ...... 24
8.1 Meta-Igneous rocks ...... 24 8.1.1 SAMPLE BH12 ...... 24 8.1.2 SAMPLE BH15 ...... 25 8.1.3 SAMPLE BH17 ...... 25 8.1.4 SAMPLE BH19 ...... 26 8.4.5 SAMPLE BH22 ...... 26 8.5 Metasedimentary rocks ...... 27 8.5.1 SAMPLE BH08 ...... 27 8.5.2 SAMPLE BH16 ...... 27 8.5.4 SAMPLE I0508 ...... 28 9. IN SITU U-PB MONAZITE GEOCHRONOLOGY ...... 28
9.1 Monazite grain morphologies ...... 28 9.2.1 SAMPLE BH08 MONAZITE RESULTS ...... 28 9.2.2 SAMPLE BH09 MONAZITE RESULTS ...... 29 9.2.3 SAMPLE BH16 MONAZITE RESULTS ...... 29 9.3.8 SAMPLE BH10 MONAZITE RESULTS ...... 29 10. ZIRCON TRACE ELEMENT RESULTS ...... 29
11. TI-IN-THERMOMETRY TEMPERATURE ESTIMATES ...... 31
12. LU-HF RESULTS ...... 32
13. INTERPRETATION OF RESULTS ...... 33
13.1 Interpretation of zircon data: U-Pb and REES ...... 33 13.2 Interpretation of monazite data ...... 37 13. DISCUSSION ...... 38
13.1 Provenance of meta-sedimentary protolith rocks ...... 38 13.1.1 TIMING OF DEPOSITION AND SOURCE CHARACTERISTICS...... 38 13.1.2 PROVENANCE TERRAINS FOR THE ONGOLE DOMAIN META- SEDIMENTARY ROCKS ...... 40 13.2 The timing and conditions of crystallisation for the metaigneous rocks ...... 43 13.4 Nature of metamorphism ...... 44 13.3 Polyphase metamorphism in the Ongole Domain? ...... 46 13.5 Tectonic implications for the Ongole Domain ...... 49 14. CONCLUSIONS ...... 51 4
15. ACKNOWLEDGEMENTS ...... 52
16. REFERENCES ...... 52
17. Figure and Table captions ...... 63
20. Tables ...... 71
21. Figures ...... 2
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ABSTRACT
The Ongole Domain, situated in the southern Eastern Ghats Belt, exposes an assemblage of granulite facies metasedimentary and metaigneous rocks that preserve fundamental evidence for the
Paleoproterozoic-Mesoproterozoic reconstruction of the supercontinent Nuna. LA-ICP-MS detrital zircon data from metasedimentary rocks constrain the timing of deposition for the sedimentary precursors, to between ca. 1850-1750 Ma. Lu-Hf isotopic data from detrital zircons provide a wide range of εHf values between -18 and +10, and TDM of ca. 3.2- 2.6 Ga. The Mesoarchean to
Paleoproterozoic detrital components display geochemical similarities with the Napier Complex, the
North Australian Craton and to a lesser extent, the North China Craton. U-Pb zircon and monazite geochronology have identified three episodes of metamorphism in the Ongole Domain; at ca. 1750,
1640 and 1590 Ma. Peak P-T estimates of 900 - 910°C and 9 - 9.2 kbar are calculated for metamorphism associated with collisional orogenesis, between ca. 1640-1590 Ma. Ti-in-zircon thermometry independently constrains the UHT conditions, yielding estimates of 935 ± 55°C. U-Pb geochronology and trace element analysis of zircon grains from metaigneous rocks confirm syn- tectonic magmatism occurred in the Ongole Domain between ca. 1640-1570 Ma. The results provide support for paleogeographic reconstructions that link the southern Eastern Ghats Belt and East
Antarctica during the late Paleoproterozoic.
Keywords: Ongole Domain, Eastern Ghats Belt, Nuna, zircon, monazite, pseudosections, Lu-Hf isotopes, Rare Earth Elements, Ti-in-zircon thermometry, UHT metamorphism
1. INTRODUCTION
The Proterozoic Eastern Ghats Belt (EGB) is a multiply deformed, granulite facies orogen exposed along south eastern peninsular India (Figure 1a). The Belt contains rocks that were formed, deformed and metamorphosed, in the Paleoproterozoic, Mesoproterozoic and Neoproterozoic (Dobmeier 2003; 6
Simmat & Raith 2008; Mukhopadhyay & Basak 2009). The rocks are frequently used as evidence to suggest India‘s involvement in the supercontinents Nuna (Rogers & Santosh 2002; Zhao et al. 2002;
Zhao et al. 2004; Hou et al. 2008; Evans & Mitchell 2011; Mohanty 2011), Rodinia (Li et al. 2008) and Gondwana (Powell et al. 1993; Meert 2003; Collins & Pisarevsky 2005).
The EGB is composed of four provinces, each characterised by distinct tectonothermal histories
(Figure 1b) (Ramakrishnan 1998; Rickers et al. 2001; Dobmeier 2003). The oldest provinces, the
Jeypore and Rengali, are considered to have either accreted to proto-India prior to the ca. 1000 Ma assembly of Rodinia (Mukhopadhyay & Basak 2009), or are thoroughly reworked fragments of the
Archean aged eastern Dharwar Craton (Ramakrishnan 2010). The centrally located Eastern Ghats
Province forms the most extensive province and underwent ultra high temperature (UHT) metamorphism and orogenesis at ca. 980-930 Ma during the amalgamation of Rodinia (Korhonen et al. 2011). The enigmatic southern Krishna Province records collisional orogenesis and high temperature metamorphism at ca. 1600 Ma (Upadhyay et al. 2009; Dobmeier 2003; Naqvi 2005), but preserves no evidence of the pervasive earliest Neoproterozoic orogenesis seen further north in the
Eastern Ghats Province (Mezger & Cosca 1999; Dobmeier et al. 2006).
Mesoproterozoic orogenesis in the Krishna Province is suggested to result from the collision of the
Antarctic Napier Complex with India (Dobmeier 2003; Simmat & Raith 2008), or between India and
Western Australia (Mohanty 2011), and is used as a piercing point in reconstructions of the
Paleoproterozoic to Mesoproterozoic supercontinent Nuna (otherwise known as Columbia; Rogers &
Santosh 2002; Zhao et al., 2004). However, there is little geochronological or isotopic data to constrain the provenance of the sedimentary precursors, or the timing of deposition, magmatism and metamorphism; in order to test the existing palaeogeographic models.
This study focuses on the Ongole Domain (Figure 1c); a poorly constrained region in the Krishna
Province that lies adjacent to the deformed margin of the Proterozoic Cuddapah Basin, and has played an integral role in the assembly of the supercontinent Nuna (Ravikant 2010; Vijaya Kumar et al. 7
2011). An integrated geochronological, metamorphic and protolith provenance study has not been attempted before in the Ongole Domain. Various methodologies are used to elucidate the tectonic and paleogeographic history of the region including: (1) U-Pb zircon geochronology and Lu-Hf isotopes in zircon, are combined to infer potential source terrains for the metasedimentary protoliths, thus placing spatial and temporal constraints on the deposition of the sedimentary protoliths; (2)
Petrological and quantitative metamorphic studies are undertaken to characterise the nature of metamorphism and delineate the associated tectonic setting; (3) U-Pb isotope analysis of in-situ zircon and monazite are used in conjunction with phase equilibria, to set upper and lower constraints on the timing of metamorphism and emplacement of igneous protoliths; and (4) Ti-in-zircon thermometry is used to define the crystallisation temperature of the metaigneous rocks, as well as to provide an additional constraint on the crystallisation temperature of metamorphic zircon overgrowths.
The geochronological, geochemical and metamorphic data presented in this study are used to propose a geodynamic model for the Paleoproterozoic to Mesoproterozoic evolution of the Krishna Province, and the Ongole Domain.
2. GEOLOGICAL BACKGROUND
2.1 The Eastern Ghats Belt
The Eastern Ghats Belt (EGB) is a NE-SW trending arcuate, composite orogenic belt that extends over 1000 km in length from the Brahmani River in the north eastern state of Orissa, to Ongole in
Andhra Pradesh, with a maximum width of 300km in the north that tapers off towards the south
(Figure 1a; Ramakrishnan 2010). In the west, the EGB is bordered by the Dharwar, Bhandara and
Singhbhum Cratons, and to the east it is bound by the Bay of Bengal. The Archaean-aged cratons are composed predominantly of tonalite-trondhjemite-granite gneiss (TTG), and host supracrustal rocks
(Bhattacharya 1996; Dobmeier 2003).
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The south-western margin of the EGB is marked by the Proterozoic Cuddapah Basin, a crescent shaped basin characterised by cyclic successions of quartzites, carbonates and shales, which rest unconformably on the crystalline basement rocks of the East Dharwar Craton (Figure 1c) (Naqvi
2005; Ramakrishnan 2010). In cross section, the basin is wedge shaped gradually increasing to a maximum depth of ~12 km at the eastern margin. The eastern half of the basin is occupied by the highly deformed and weakly metamorphosed Nallamalai Fold Belt. The fold belt is suggested to have developed during episodic deformation (Mukherjee 2001), but the timing of these events remains poorly constrained (Chaudhuri et al. 2002; Saha 2002).
Traditionally, the EGB was viewed as a contiguous granulite terrane that was formed and reworked during several major orogenic events throughout the Paleoproterozoic, Mesoproterozoic and
Neoproterozoic (Dobmeier 2003). A number of authors have previously subdivided the belt on the basis of lithological (Ramakrishnan 1998), or geochemical characteristics (Rickers et al., 2001).
However, evaluation of recent geological and isotopic data by Dobmeier and Raith (2003) has identified four new crustal provinces with distinct tectonic evolutions (Dobmeier 2003). These are the
Krishna Province, the Jeypore Province, the Rengali Province and the Eastern Ghats Province (Figure
1b). For the purpose of this study, this is the classification system that will be adopted.
2.2 The Krishna Province and Ongole Domain
The Krishna Province is comprised of the granulite-facies Ongole Domain in the east, and the low to medium grade Nellore Schist Belt (NSB) in the west (Figure 1c). The NSB is juxtaposed against the
Nallamallai Fold Belt along the Vellikonda thrust front, which is interpreted to represent a major intracontinental thrust (Saha 2011). The belt is subdivided into the greenschist-facies Udayagiri
Domain, and the amphibolite-facies Vinjamuru Domain. The NSB consists of volcano-sedimentary pelites, psammites and gneisses of increasing metamorphic grade towards the east. U-Pb zircon ages of 1868 ± 6 Ma and 1771 ± 8 Ma constrain the timing of felsic volcanism in the NSB (Vasuden 2003).
In addition to the metamorphosed volcano-sedimentary rocks; thrust faults, ophiolites and tectonic 9 mélange along the south eastern boundary of the NSB, have been interpreted as fragments of
Proterozoic sutures that separate the NSB from the Ongole Domain (Kumar & Leelanandam 2008;
Kumar et al. 2010; Dharma Rao et al. 2011b; Dharma Rao et al. 2011c).
The Ongole Domain is comprised predominantly of mafic granulites and plutonic felsic granulites; that usually include hypersphene bearing charnockites, enderbites or leucocratic orthogneiss interlayered with porphyritic leptynites (Dobmeier 2003). Zircon U-Pb isotope data from charnockites and enderbites suggest crystallization between ca. 1720-1700 Ma (Kovach et al. 2001). The same rocks yield Nd model ages of between 2.5 and 2.3 Ga (Rickers et al., 2001). The intrusive bodies are heavily deformed and invaded by a pervasive network of allanite-bearing pegmatites (Kovach et al.,
2001).
Metasedimentary rocks are scarce, occurring mostly in the east of the domain, as partly absorbed, layers within the intrusive igneous bodies (Dobmeier 2003). Metapelitic rocks preserve distinct, high temperature mineral assemblages. Migmatitic garnet – sillimanite – spinel - corundum granulites dominate, but quartzites, garnet-opx gneisses and calc-silicate granulites are also frequently preserved
(Sengupta et al. 1996; Dobmeier 2003). Metasedimentary granulites are commonly intruded by garnet bearing leucosomes (Mukhopadhyay & Basak 2009). The timing of deposition and detrital provenance for the metasediments are still unknown. Nd model ages of metasediments yield ages of
2.8 to 2.6 Ga, which have been correlated with the abundant granitoids of the Eastern Dharwar Craton
(Rickers et al., 2001).
Recent Laser Inductively Coupled Mass Spectrometry (LA-ICP-MS) U-Pb zircons data from metapelitic rocks produced concordant ages of ca. 1630 Ma for cores and ca. 1610 Ma for rims
(Upadhyay et al. 2009). Poor CL and a lack of internal zonation in zircon grains are used as evidence to suggest isotopic resetting during UHT metamorphism at ca. 1630 Ma (Upadhyay et al. 2009).
Monazite grains from the same rocks produced four peak ages at ca. 3450, 2500, 1580 and 1480 Ma.
The oldest grains are interpreted to be detrital; whereas the ca. 1580 Ma grains are suggested to 10 constrain the timing of metamorphism. The ca. 1480 Ma monazite grains are interpreted to have recrystallised during localised ductile to brittle deformation in the late Mesoproterozoic (Simmat &
Raith 2008; Upahyay et al.2009).
An understanding of the tectonic evolution of the Ongole Domain is hampered by the paucity of geological data, and as a result is poorly constrained (Dobmeier 2003; Bhui et al. 2007; Simmat &
Raith 2008; Dharma Rao et al. 2011a). Recognition of oceanic sutures in the Krishna Province invariably suggests that an active continental margin, with associated subduction and arc related magmatism, preceded the emplacement of ophiolites within the Indian crust (Dharma Rao et al.,
2011b). The bimodal granulites preserved in the Ongole Domain exhibit geochemical signatures indicative of arc-related magmatism, and are interpreted to represent the roots of a subduction zone that operated prior to ca. 1600 Ma terminal continental collision in the Mesoproterozoic
(Bhattacharya & Chaudhary 2010; Vijaya Kumar et al. 2010; Dharma Rao et al., 2011b).
2.3 Metamorphism in the Ongole Domain
The absolute P-T conditions and timing of the dominant granulite-facies metamorphism within the
Ongole Domain are poorly constrained. Dasgupta et al. (2008) report contact metamorphism along an anticlockwise pathway at the boundary of the Chimarkurthy Mafic Complex. Two-pyroxene thermometry indicates that metamorphism occurred at ~6 kbar and 750-1110°C (Dasgupta et al.,
2008). Similar conditions were described at the contact zone of the Kondapalle Mafic Complex, where metamorphism reached UHT conditions at 8kbar and >1000°C (Sengupta et al. 1999). A single
U-Pb age from a monazite grain within a synkinematic pegmatite produced an age of 1672 ± 3 Ma, and is suggested as an absolute age for the granulite-facies metamorphism (Kovach et al., 2001).
The possibility of a high-grade metamorphic event prior to ca. 1700-1600 Ma has been documented by a number of authors (Dobmeier 2003; Bhui et al., 2007; Simmat & Raith 2008; Mukhopadhyay &
Basak 2009; Bose et al. 2011). A cluster (n=7) of 1760 Ma concordant zircon grains from a deformed, 11 migmatite gneiss are used as evidence to suggest the age of an earlier metamorphic event (Bose et al.,
2011) in the Ongole Domain.
3. STRUCTURAL SETTING AND FIELD RELATIONSHIPS
3.1 Structural and field work overview
The structural geometry and deformational history of the EGB are poorly constrained and frequently debated (Mukhopadhyay & Basak 2009). A study linking structure and deformation has not been conducted within the Ongole Domain (Gupta & Bose 2004). Based on the level and quality of exposed outcrop in the Ongole Domain, two domains were targeted for geochronological and metamorphic analysis. Domain 1 (Figure 2a) is located in the south east of the Ongole Domain, and
Domain 2 is situated approximately 70 km north of Domain 1 (Figure 2b).
Deformational, mineralogical and structural characteristics are used to infer relative relationships between the meta-igneous units in the study areas, as contact relationships are often obscured beneath younger cover sequences. Detailed outcrop analysis and key relationships are summarised in Tables 1,
2, 3 and 4 in Appendix II. Samples were selected for geochronology and quantitative metamorphic analysis, on the basis of preservation of tectonic features and distinct mineral assemblages.
3.1.2 DOMAIN 1
The oldest lithologies recognised in Domain 1 are garnet-sillimanite metapelite (Sample BH08/09) and aphanitic metabasite (Figure 3a, b). Both units occur as xenoliths (~1-25 m2) within an intrusive pyroxenite (Figure 3c), and are strongly foliated and isoclinally folded. Two dominant fabrics are preserved in Domain 1; the first is a pervasive, steeply dipping N-NW fabric within the metabasite and metapelite. Sillimanite defines the fabric in the metapelites, wrapping around ~10-150 mm garnet porphyroblasts (Figure 3d, e). The foliation dip and fold axes plunge steeply to the N-NW, implying that if the xenoliths retained their original orientation, then both structural features were likely to be imprinted at the same time. The second fabric is a steep, westerly dipping foliation preserved within 12 the pyroxenite, which encloses the metapelite and metabasite. The metapelite is intruded by syn to post deformational, foliation-parallel garnet bearing granites (Sample BH10); which preserve kinematic indicators which suggest the hanging wall moved to the east (Figure 3f). The enclosing pyroxenite is composed largely of medium grained pyroxene and plagioclase and is strongly foliated, but no folding could be seen. Approximately 10 cm wide coarse-grained, orthopyroxene bearing veins cross cut the fabric in the pyroxenite. Quartz and K-feldspar rich, coarse grained granites cross cut the metapelite and the garnet bearing granite intrusion (Figure 3g). Coarse grained undeformed,
N-S trending, granitic dykes cross cut all lithologies (Figure 3h).
3.1.3 DOMAIN 2
The oldest lithologies recognised in Domain 2 are two metasedimentary xenoliths preserved within deformed charnockites and granitic gneisses. The first, a massively layered, foliated garnet- orthopyroxene-gneiss (Sample BH16) is preserved within a weakly deformed leucocratic gneiss
(Sample BH19). A strong westerly dipping, planar fabric is preserved within the garnet-bearing gneiss gneiss, defined by elongate, deformed quartz, K-feldspar and minor biotite grains. The fabric is truncated by a weak, steeply dipping N-NW fabric preserved within the leucocratic gneiss.
Well layered quartzofeldspathic gneiss (sample I0508) is the second metasedimentary unit sampled in
Domain 2. This sample was selected on a previous field trip (Collins pers.comm). Medium-grained, quartz, feldspar and biotite grains define a steep northerly dipping foliation, which is preferentially intruded by coarse-grained, K-feldspar leucosomes. Enclosing the quartzofeldspathic gneiss is a strongly deformed, charnockite body. The charnockite is dark green to grey in colour and comprised of elongate OPX grains, large, ~5cm phenocrysts of K-feldspar and fine-grained plates of biotite which define a steep, SW-W planar fabric through the rocks. A network of thick (~30-50 cm wide), allanite-bearing pegmatites (Figure 4a, b) intrude the charnockites. The pegmatites have diffuse boundaries up to 1.5 m thick (Figure 4a), which contain high abundances of biotite and are a distinct pinkish colour by comparison to the surrounding rock. Pegmatites are interpreted to have been 13 emplaced prior to deformation, as the dominant westerly-dipping fabric overprints the charnockite and pegmatites (Figure 4c).
Sample BH15 was selected approximately 1 km east of BH12, from within the same charnockite body. It is a coarse-grained, undeformed diatexite comprised of K-feldspar, quartz and OPX that grades into the strongly deformed charnockite body (Figure 4d, e). Isoclinally folded mafic xenoliths are hosted within the diatexite. Both lithologies are dissected by a series of ~30cm wide N-NW trending, ultra-mylonite shear zones (Figure 4f). Lineations within the shear fabric consistently indicate top to the north. All lithologies are cross cut by fine grained, undeformed mafic dykes with chilled margins (Figure 4g).
Sample BH17 was collected in a quarry from a charnockite, which bears a similar mineralogy to sample BH12. In the north of the quarry, the foliation is pervasive and predominantly dips S-SE, but towards the south it is weak and discontinuous. The charnockite encloses amphibolitic xenoliths, which preserves a steep easterly dipping fabric (Figure 5a). Garnet bearing pegmatites intrude and dissect the xenoliths. Boudinage within the amphibolite and extensional fabrics in the charnockite suggest localised extension (Figure 5c, d). Multiple generations of pegmatite intrusion are preserved; the oldest exhibits a fabric that is cross cut by younger, undeformed pegmatites (Figure 5d). Fine grained, ~1-1.5 m wide mafic dykes cross cut all lithologies (Figure 5b).
The western half of the study region is dominated by topographically low granite hills of varying lithologies, including diorites, granodiorites and megacrystic granites (Figures 5f, g, h, i). Most granites are weakly to strongly foliated W-NW, and contain xenoliths of deformed metabasites. All granites show evidence of partial melting; preserving anastomosing networks of pervasive leucosomes
(Figure 5g). Sample BH22 is weakly foliated granite that intrudes a weakly foliated charnockites
(Figure 5f). BH22 preserves isoclinally folded, diffuse leucosomes that dip at ~ 45° to the N-NW.
Megacrystic granites preserve lenticular xenoliths of metabasite; and coarse grained, undeformed pegmatites (Figures 5g, i). 14
4. PETROGRAPHY
Samples are ascribed to six groups that represent the main lithological units present in the Ongole
Domain. They are: 1) pyroxene bearing meta-granites, 2) garnet bearing granites, 3) meta- granodiorites, 4) meta-granites, 5) quartzofeldspathic gneiss, and 6) garnet bearing meta-sedimentary rocks.
4.1 Pyroxene bearing meta-granites (charnockites)
Sample BH12 is composed of K-feldspar + quartz + perthite + plagioclase + antiperthite + orthopyroxene + magnetite + biotite. The rock preserves a strong gneissic fabric, defined by biotite,
K-feldspar porphyroblasts and magnetite (Figure 6a). Two types of quartz are evident. The first are 1-
2 mm crystals that preserve strained and deformed textures and are recrystallised, aligning with matrix foliation. The second are small (<0.5 mm) anhedral grains, with interlocking 120° boundaries with subhedral laths of plagioclase (1-2 mm). The latter form rims around K-feldspar grains, or as mosaic aggregations with plagioclase in ‗pressure shadows‘ at the terminations of deformed K-feldspar grains
(Figure 6b). K-feldspar grains are large (10-20 mm in length, 10 mm in width), and form lenticular
‗augen‘ shapes parallel to the foliation plane in sample BH12 (Figure 6a). Some grains exhibit simple twinning, and are commonly perthitic. Biotite grains make up ~5-10 % of the rock and are straw brown in plane polarised light (PPL), and dark brown in cross polarised light (CPL). Individual crystals are euhedral, tabular grains (1-3 mm) that form dense mats with magnetite, which wrap around K-feldspar grains in BH12 (Figure 6b). Orthopyroxene is rare in sample BH12 (~0.5%), preserved as small (<2 mm) grains that are always spatially associated with biotite, or magnetite grains.
Samples BH15 and BH17 are composed of a similar mineral assemblage to BH12, but contain both orthopyroxene and clinopyroxene, and <1% biotite. The rocks preserve a weak gneissic fabric, which is defined by the preferred alignment of K-feldspar porphyroblasts, clinopyroxene and orthopyroxene 15
(Figure 6c). Orthopyroxene (0.5-2 mm) and clinopyroxene (0.1-1 mm) have a clear spatial association with one another, where orthopyroxene frequently forms incomplete rims around clinopyroxene.
Clinopyroxene preserves basal twinning and exsolution textures (Figure 6d). K-feldspar porphyroblasts (10-30 mm) are euhedral in shape and do not preserve the same deformed, augen shape seen within BH12. K-feldspar grains preserve large crystals (10-20 mm in length) of anti- perthite (Figure 6e). Myrmekitic intergrowths of quartz and plagioclase are common at the boundary of K-feldspar grains. Biotite is restricted to cracks within and around pyroxene crystals.
4.2 Garnet-bearing granite
Sample BH10 was taken from a weakly deformed garnet + quartz + K-feldspar + perthite + antiperthite granite, which intrudes parallel to the foliation of a garnet-sillimanite-metapelite (Sample
BH08/09). Anhedral, deformed, quartz grains (0.5-4 mm) with irregular grain boundaries comprise
70% of the rock, and are commonly associated with subhedral laths of perthite and antiperthite (0.2-5 mm) (Figure 6f). Small interstitial grains of quartz fill cracks between larger grains of perthite, antiperthite and quartz. Rare, poikiloblastic, anhedral garnet grains (1-2 mm) contain rounded quartz and monazite inclusions (Figure 6g).
Anhedral clusters (1-5 mm) of cordierite, sillimanite, biotite and orthoamphibole are randomly distributed throughout the rock (Figure 6h). They exhibit a consistent internal order whereby cordierite is surrounded by fine grained rims (1-2mm) of fine-grained sillimanite, biotite and orthoamphibole. Cordierite, sillimanite and orthoamphibole are restricted to these clusters. Magnetite and ilmenite are occasionally preserved within the fibrous rims, but are also distributed randomly throughout the rock. Tabular, euhedral biotite grains (1-3 mm) are preserved within the quartz- feldspar matrix of the rock. Monazite grains are extremely common in the quartz-feldspar matrix and cordierite + sillimanite + orthoamphibole + biotite clusters, forming large anhedral to euhedral grains up to 0.5 mm in size.
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4.3 Metagranodiorites
The metagranodiorite (sample BH19) is composed of quartz + plagioclase + perthite + biotite. Two types of quartz grains are seen in this rock; the first are ~1-5 mm in size, deformed with irregular, interlocking grain boundaries, and the second are small (<0.2 mm) anhedral, interstitial grains, which fill grain boundaries and cracks of larger minerals. Plagioclase and perthite grains are subhedral to anhedral in shape, and vary in size between 0.5-4 mm (Figure 6i). Biotite grains (0.1-0.5 mm) form in mats that are commonly interwoven with interstitial quartz grains. Large, elongate quartz and biotite grains define a weak fabric through the rock. Accessory zircon and magnetite grains are preserved within the plagioclase, perthite and quartz grains.
4.4 Metagranites
Sample BH22 is composed of quartz + perthite + plagioclase + biotite + hornblende. Perthite forms subhedral laths (1-3 mm) with irregular, grain boundaries. Myrmekitic texture is common at the interface between perthite and quartz. Perthitic textures preserved are highly variable, including; blebby strings of mesoperthite, fine grained, spindle-like perthite, and anastomosing lamellae networks. Quartz grains are either granoblastic (0.5-2 mm), anhedral crystals that preserve interlocking boundaries with perthite, hornblende and biotite, or are small (<0.5 mm) interstitial grains forming between larger minerals (Figure 6j). Hornblende grains (0.5-3 mm) are commonly skeletal, and are spatially associated with biotite, which often appears within and around hornblende
(Figure 6k). Biotite (0.1-0.5 mm) forms euhedral, tabular to platy grains in clusters with hornblende and accessory magnetite. Prismatic to subrounded zircon is a common accessory mineral, preserved within biotite, perthite and magnetite. A very weak fabric is present, defined by biotite and hornblende.
4.5 Quartzofeldspathic gneiss
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Quartzofeldspathic gneiss (sample I0508) is comprised of quartz + perthite + sillimanite (Photo 1N,
O). No dominant fabric is present in the rock, but sillimanite is weakly oriented along one plane
(Figure 6i). Quartz grains comprise >70% of the rock and are strongly deformed and recrystallised, exhibiting characteristic 120° grain boundaries. Perthite forms (2-10 mm) coarse, anhedral grains that frequently contain rounded quartz inclusions. Fine, anastomosing lamellae of sodic feldspar are the most common exsolution texture preserved. Thin needles of sillimanite (0.2-1 mm) grow over the top of the quartz and perthite grains. A second population of sillimanite is also preserved, forming tabular laths (0.5-1 mm), which overlie quartz, perthite and thin sillimanite grains. Accessory ilmenite grains
(<0.5 mm) are sporadically scattered throughout the rock. Small, flecks of biotite (<0.5 mm) are usually associated with ilmenite grains.
4.6 Garnet bearing meta-sedimentary rocks
BH08 and BH09 are composed of garnet + quartz + sillimanite + cordierite + K-feldspar + ilmenite + magnetite + biotite. Several discrete forms are garnet are preserved. Garnet one (G1), is coarse grained (5-15 mm), commonly poikiloblastic, porphyroblasts containing pervasive inclusions of fibrous sillimanite, subrounded quartz, K-feldspar, ilmenite and biotite (Figure 7a). The cores of some of the G1 grains are inclusion free. Garnet two (G2) is intergrown with vermicular symplectites of ilmenite, which commonly form around as rims around the grain boundaries of G1 (Figure 7b).
Biotite (0.5-2 mm) forms dark brown, euhedral platey grains that are only located predominantly within G1 garnet, and are normally associated with magnetite. The matrix of the rock comprises of cordierite, sillimanite, K-feldspar, quartz, ilmenite and magnetite (Figure 7c). Rare grains of spinel
(0.1-0.5 mm) are preserved on, or within magnetite grains. Magnetite grains are anhedral and vary in size between 0.5-3 mm. Cordierite tends to form in K-feldspar and quartz rich domains, and occasionally contains inclusions of skeletal garnet (G1) grain (Figure 7c), and small grains of apatite
(0.1-0.5 mm) (Figure 7d). Cordierite is frequently surrounded by thick rims (1-2 mm) of fine grained sillimanite + orthoamphibole + biotite ± rutile. Small subrounded grains of rutile (0.5-1 mm) are present within the rims. Sillimanite embodies several forms within the rock :1) small (≤ 0.5 mm) 18 fibrous needles throughout garnet porphyroblasts that are truncated at the grain boundaries; 2) elongate, needles and laths (1- 10 mm) of sillimanite that define the dominant foliation, within the matrix of the rock, and 3) large laths (10 mm) that cross cut the fabric defining sillimanite. A well developed fabric is present within the rock defined by sillimanite that wraps around the garnet porphyroblasts.
Sample BH16 comprises of garnet + orthopyroxene + ilmenite + plagioclase + K-feldspar + perthite + antiperthite + biotite (Figure 7e). Coarse, equant garnet grains (0.1-0.8 mm) are typically fractured, and contain rounded monazite and ilmenite inclusions (Figure 7f). Fine grained biotite (0.1-0.5 mm) occasionally grows within the cracks of garnet, or around the outside of the grains. Anhedral orthopyroxene grains (0.1- 5 mm) are heavily fractured and are preserved in direct contact with garnet grains (Figure 7g). Orthopyroxene is usually heavily fractured, and spatially associated with biotite in nearly all cases. Quartz grains (1-2 mm) are strained and recrystallised, and have irregular interlocking boundaries with feldspars and other quartz grains. Fine grained, interstitial quartz grains commonly fill gaps between larger minerals. Ilmenite forms as cuspate grains within fractures of OPX and garnet, or is often completely embayed within the porphyroblastic minerals. Coarse grained K- feldspar and plagioclase are abundant, but coarse-grained (1-2 mm) antiperthite and perthite are also common. The rock preserves a weak fabric defined by elongate, deformed quartz, and feldspar minerals.
4.7 Interpreted petrogenesis of the metasedimentary rocks
Sample BH08 (and BH09) are heterogeneous at microscopic scale and preserve sub-assemblages that developed primarily at the expense of garnet in the first instance, and then subsequently cordierite.
The key mineral reaction textures are:
1. The partial replacement of a garnet-sillimanite-ilmenite bearing association by corderite,
resulting in the formation of a garnet-sillimanite-cordierite association. 19
2. The subsequent replacement of cordierite to varying degrees by fine-grained intergrowths of
sillimanite-orthoamphibole-garnet with minor rutile and ilmenite.
The peak metamorphic assemblage is interpreted to be garnet (G1) + sillimanite + ilmenite + magnetite + K-feldspar + quartz +/- biotite. The truncation of sillimanite inclusion trails hosted within peak garnet grains (G1) by cordierite, suggest that cordierite grew at the expense of garnet and sillimanite (Kato et al. 2010). This relationship is best illustrated in Figure 8.1 where a large moat of cordierite completely embays a skeletal garnet (G1) grain. Consequently, the cordierite crystal
‗pseudomorphs‘ the relic garnet grains as the reaction takes place (Figure 8.2). A dominant secondary mineral assemblage of sillimanite + orthoamphibole + garnet has subsequently developed at the expense of cordierite. In some domains this reaction is preserved as fine grained rims around cordierite (e.g. Figure 7d); and in others total replacement of cordierite has occurred resulting in dense
‗mats‘ of sillimanite and orthoamphibole (Figure 8.3). Coinciding with this reaction is the growth of secondary garnet (G2), which frequently forms intricate, symplectic growths with ilmenite/magnetite.
The replacement of cordierite and the formation of G2 is interpreted to form in response to near isobaric to isobaric cooling (e.g. Appel et al. 1998). G2 commonly forms distinct rims around remaining G1 grains (Figure 8.4).
The peak mineral assemblage in sample BH16 is interpreted to be garnet + orthopyroxene + ilmenite
+ quartz + K-feldspar + plagioclase. Garnet and orthopyroxene grains are preserved in equilibrium contact with one another (e.g. Figure 7g) throughout the rock. The rock is interpreted to have undergone some retrogression following peak metamorphism, but nothing as extensive as that seen in sample BH08/BH09. Post-peak biotite grains form quite pervasive rims around orthopyroxene, almost completely replacing it in some areas. Retrograde biotite also forms around the edges and within the cracks of some garnet grains. Retrogression to biotite is interpreted to have formed at the expense of orthopyroxene and garnet during cooling (e.g. Brandt et al. 2007). 20
5. METHODOLOGIES
5.1 Quantified metamorphic analysis: P-T pseudosections
The main tool for determining P-T conditions in a metamorphic rock is the application of thermodynamics (Powell & Holland 2010). P-T pseudosections are considered to be the most powerful method available, as they allow visualisation of multivariant mineral assemblages and univariant mineral reactions, for a specified bulk rock composition. A P-T pseudosection based on the whole rock composition of sample BH16 was calculated in the model system MnO–NaO–CaO–K2O–
FeO–MgO–Al2O3–SiO2–H2O–TiO2 (MnNCKFMASHT) using THERMOCALC v. 3.26 (Powell &
Holland 1988; Powell & Holland 2010). EPMA was employed to obtain spot chemical analyses for phase diagram compositional isopleths. The whole rock chemistry of sample BH16, as well as BH08,
BH09 and I0508 are included in Table 5. A full description of the methods followed is included in
Appendix I.
5.2 LA-ICP-MS U-Pb zircon and monazite geochronology
LA-ICP-MS U-Pb zircon geochronology was conducted on eight samples (BH08, BH12, BH15,
BH16 BH17, BH19, BH22, I0508), and insitu monazite geochronology was conducted on three samples (BH08, BH09, BH16). The samples were chosen from a variety of lithologies in both domains, to best represent the tectonic evolution of the Ongole Domain. Methods follow that of
Payne et al. (2006a; 2008) and a full description of the techniques followed is included in Appendix I.
5.3 LA-ICP-MS trace element analysis (Rare Earth Elements and Ti-in-zircon thermometry)
LA-ICP-MS trace element data were collected for samples BH08, BH16, I0508, BH15 and BH17, for
Ti-in-zircon thermometry and rare earth element (REE) analysis. The concentration of REEs in zircon allow for the timing of crystallisation to be linked to the conditions of petrogenesis, and the presence of coexisting metamorphic minerals, such as garnet or feldspars (Rubatto 2002; Hanchar & van 21
Westrenen 2007). The Ti content of zircon is largely a function of the crystallisation temperature, and is employed in this study to provide an independent constraint on the conditions of metamorphism
(Watson & Harrison 2005; Ferry & Watson 2007). Ti-in-zircon thermometry is also utilised to define the crystallisation temperature of the protolith igneous rocks (BH15, BH17). Methods for Ti-in-zircon temperature and trace element analysis follow that of Clark et al. (2009). A summary of the steps followed, and a full description of Ti-in-zircon technique, is included in Appendix I.
5.4 LA-MC-ICP-MS Lu/Hf isotopes
Zircon has the capacity to retain its primary Lu-Hf isotopic signature through granulite-facies metamorphism, due largely to its ability to remain a closed system during isotopic resetting (Iizuka et al. 2009). The technique is used in conjunction with U-Pb zircon data to constrain regions of sedimentary provenance. Lu - Hf isotopes in zircon were collected for samples BH08, BH16 and
I0508, following methods of Teale et al. (2011), with a detailed description of the techniques followed is included in Appendix I.
6. RESULTS
6.1 Mineral chemistry
The chemical compositions of the minerals in samples BH08, BH09 and BH16 were determined by
Electron Microprobe Analysis (EPMA) at Adelaide Microscopy. Metapelitic rocks were preferentially selected for this technique, as their diverse chemistry means they have the largest number of possible mineral assemblages that can be used to constrain the P-T conditions experienced by the rock (White et al 2007). The Fe3+ of minerals was determined using the Ax software of Holland & Powell (1998).
A full description the technique followed is included in Appendix I, and a representative summary of the results is included in Table 6.
6.1.1 GARNET 22
Garnet in sample BH08 is dominated by almandine-pyrope solid solution that ranges in XAlm from
2+ 2+ 0.509 to 0.552 and XPy from 0.396 to 0.441, where XAlm=Fe /(Fe + Mg + Ca + Mn) and XPy=
Mg/(Fe2+ + Mg +Ca + Mn). Garnet profiles show some local variation, but no zonation patterns are consistent (Figure in Appendix II). Only G1 garnet grains were analysed for chemical composition.
BH09 is also dominated by almandine-pyrope solid solution where XAlm ranges from 0.507-0.556 and
XPy is 0.204-0.436. However, some garnet profiles show evidence of XAlm decreasing towards the rims of the grains, and a corresponding increase in XPy. No chemical zonation is seen within the garnet grains (Appendix II). Only G1 garnet grains were analysed for chemical composition.
Garnet grains from sample BH16 are almandine rich with variable pyrope concentration. XAlm is
0.63-0.707 and XPy is 0.213-0.305. Localised variability exists at the rims of some grains, where pyrope increases at the expense of almandine (Appendix II).
6.1.2 FELDSPARS
Sample BH16 has approximately equal quantities of plagioclase and potassium feldspar. Plagioclase is almost equally sodic and calcic, where XAb (=Na/ (K + Na + Ca)) ranges from 0.56-0.59, and XAn (=
Ca/ (Ca + Na)) ranges from 0.40-0.43. K-feldspar grains are dominantly potassic where XOr (= K/ (K
+ Na)) values range from 0.80-0.97, with minor percentages of albite (XAb =0.02-0.18) and trace amounts of anorthite (XAn = 0.02-0.27).
The majority of plagioclase in sample BH09 are dominantly albite (XAb= 0.59-0.65), and some anorthite (XAn= 0.32-0.39). Several plagioclase grains however were largely calcic (XAn=0.61-0.79), with minor albite (XAb = 0.16-0.38) XOr is negligible in all cases (<0.008).
6.1.3 CORDIERITE
23
Cordierite in samples BH08 and BH09 are very strongly magnesian with XMg values of 0.87-0.89,
2+ where XMg= Mg/ (Fe + Mg). XFe is 0.11 to 0.12 where XFe = Fe/ (Mg+Fe). Mn contents are <0.002 per 18 oxygen unit in BH08, but are slightly higher in BH09 ranging between 0.016-0.07. Total alkali contents are <0.07 cations per 18 oxygen unit in both samples.
6.1.4 ILMENITE
Ilmenite in BH08 and BH09 are relatively TiO2 poor, ranging between 20-32 wt % TiO2, compared to the BH16 where ilmenite has ~52 wt % TiO2. BH16 is entirely reduced, in contrast to the more oxidised BH08 and BH09 [(Fe3+/(Fe3+ + Fe2+) = 0.56- 0.79].
6.1.5 MAGNETITE
Magnetite appears in samples BH08 and BH09. BH08 has an Al2O3 content of 0.19-1.117 wt %,
3+ which corresponds to XAl (Al/ (Al+Fe +TiO2) of 0.0306 to 0.0046. The TiO2 content of BH08 is 0.01 wt%. BH09 has a lower Al2O3 content of 0.149 to 0.165 wt %, corresponding to XAl of 0.0035-
0.0040. The TiO2 content of BH09 is < 0.001 wt%.
6.1.6 ORTHOPYROXENE
Orthopyroxene appears in sample BH16. All orthopyroxene analysed has an XFe of 0.50-0.53 where
3+ 2+ 3+ 2+ XFe = Fe/Mg + Fe + Fe + Ca + Mn and Fe = Fe + Fe + Ca, and XMg of 0.47-0.49 where XMg=
Mg/Mg + Fe3++ Fe2++ Ca + Mn). Al ranges from 0.105 - 0.215 per 6 oxygen unit. Orthopyroxene grains yield yopx values of approximately 0.083; where yopx = Al - 2 +Si.
6.1.7 BIOTITE
24
Biotite in sample BH16 is has XMg of approximately 0.63, and has TiO2 of ~4.5 wt %. BH08 and
BH09 have XMg of approximately 0.76 and Ti O2 of ~5 wt %.
7. CALCULATED PHASE DIAGRAM
A phase diagram calculated for the bulk composition of sample BH16 is shown in Figure 9. The interpreted peak mineral assemblage is garnet + orthopyroxene + K-feldspar + plagioclase + ilmenite
+quartz. The sample has been contoured for the aluminium content of orthopyroxene [y(opx)] and x(g)
(=Fe/Fe + Mg) of garnet grains. Garnet compositional isopleths indicate that x(g) values increase down pressure, and y(opx) values decrease up pressure. In the peak field the y(opx) values are 0.083 and the x(g) values are 0.70 (see 6.1.6), constraining the peak mineral assemblage to pressures of ~9-
9.2 kbar and temperatures of 900-910° C.
8. ZIRCON DESCRIPTIONS AND RESULTS
The results from U-Pb zircon analyses from eight samples are discussed below. A number of analyses were omitted due to the presence of 204Pb or inconsistent and chaotic spectrometry signal; these are denoted in red in Table 7 in Appendix II. Detailed descriptions of internal and external of the zircons analysed is displayed in Tables 8a and 8b. Weighted average calculations presented for grains
>1000Ma are 207Pb/206Pb ages, and those <1000 Ma are 206Pb/238U ages. Conventional concordia diagrams and weighted average plots for samples BH12, BH15, BH17, BH19 and BH22 are shown in
Figures 10-14. Conventional concordia diagrams, weighted average plots and combined probability density plots for samples BH08, BH16 and I0508 are shown in Figures 15-17.
8.1 Meta-Igneous rocks
8.1.1 SAMPLE BH12
25
In sample BH12, 85 spots were ablated on 50 zircons, which targeted weakly luminous cores, rims and well preserved oscillatory zoning (Figure 10a). Of the 85 analyses, 79 were between 90-110% concordant (Figure 10b). A weighted average of all concordant 207Pb/206Pb analyses produces an age of 1636 ± 5 Ma with an MSWD of 0.80 (Figure 10c). Weighted averages for weakly luminescent cores, rims and oscillatory zoning yield age estimates of 1633 ± 8 Ma (MSWD=0.85), 1639 ± 9 Ma
(MSWD= 0.72) and 1639 ± 8 Ma (MSWD=0.83). As all age estimates fall within error of one another, the best approximation of the crystallisation age is the weighted average age of all analyses.
8.1.2 SAMPLE BH15
Seventy two analyses were obtained from 32 zircons from sample BH15, which targeted luminous rims, oscillatory-zoning and convoluted domains (Figure 11a). Of the 72 analyses 68 were between
90-110% concordant (Figure 11b). A weighted average 207Pb/206Pb age of the oscillatory-zoned cores produced an age estimate of 1633 ± 8 Ma (MSWD=1.2; Figure 11C) and convoluted cores yield a weighted average of 1637 ± 9 Ma (MSWD=1.5). Strongly luminescent rims generate a younger
207Pb/206Pb weighted mean of 1617 ± 7 Ma (MSWD=0.77). The domains yield ages just outside 2σ error of each other, and are interpreted as real age differences between crystallisation of the protolith magmatic zircon and later zircon growth.
8.1.3 SAMPLE BH17
Fifty four spots were analysed on 40 zircon grains from sample BH17, which targeted four specific
CL domains. These are: homogenous weakly luminescent cores, weakly luminescent rims, patchy or convoluted cores, and well-preserved oscillatory-zoning (Figure 12a). All grains analysed were 90-
110% concordant (Figure 12b). Collectively, all concordant data generate a weighted average age estimate of 1578 ± 7 Ma with an MSWD of 1.3 (Figure 12c). The ages of homogenous and convoluted cores are inseparable and yield average ages of 1577 ± 16 Ma (MSWD=0.93) and 1578 ±
10 Ma. Weakly luminescent rims yield a slightly younger weighted average age of 1570 ± 12 Ma. 26
Oscillatory-zoned domains generate a weighted average of 1601 ± 17 Ma (MSWD=0.47). Although there is some variation in the targeted domains, with the oldest ages being from the cores and the younger from the rims, the imprecision of the LA-ICPMS technique means that all results fall within error of one another and the collective weighted average age is considered the most accurate approximation of crystallisation.
8.1.4 SAMPLE BH19
Fifty six analyses were obtained on 47 zircon grains from sample BH19. Ablation targeted patchy, convoluted zoning in cores and strongly luminescent rims (Figure 13a). 28 of the 56 results were between 90-110% concordant. A discordia constructed from all data produces an upper intercept of
1617 ± 21 Ma (MSWD= 1.2) (Figure 13b), which is within error of the weighted average age of concordant analyses (1617 ± 10 Ma; MSWD= 1.2; Figure 13c). Convoluted cores generate a weighted average age estimate of 1621 ± 12 Ma (MSWD=1.4), and strongly luminescent rims yield a weighted average age of 1607 ± 17 Ma (MSWD=0.051). The CL domains are statistically indistinguishable and thus the weighted average of all samples is the most reliable representation of the zircon crystallisation.
8.4.5 SAMPLE BH22
Fifty six spots were ablated on 47 zircon grains from sample BH22, targeting homogenous and xenocrystic cores, strongly luminescent domains and weakly luminescent rims (Figure 14a). Forty seven of 54 analyses were between 90-110% concordant (Figure 14b). Collectively, all analyses yield a weighted average age estimate of 1597 ± 6 Ma (MSWD=0.44; Figure 14c). All individual domains are statistically identical to the cumulative weighted average generating age estimates of 1597 ± 11
Ma, 1529 ± 19 Ma and 1598 ± 8 Ma for homogenous cores (MSWD=0.52), luminescent domains
(MSWD=0.18), and weakly luminescent rims (MSWD=0.47) respectively. The domains are 27 statistically indistinguishable and thus the weighted average of all samples is the most reliable representation of the zircon crystallisation age.
8.5 Metasedimentary rocks
8.5.1 SAMPLE BH08
In sample BH08, 132 spots were ablated on 71 grains, which targeted oscillatory-zoning, homogenous cores, rims and convoluted cores (Figures 15a, b). A probability density plot shows two broad populations between ca. 1780 - 1720 Ma, ca. 1890-1810 Ma (Figure 15d). The data from the peaks were processed using ‗unmix‘ (Ludwig 2003; Figure 15c), which divides the peaks into two distinct populations which yield weighted averages of age of 1756 ± 9 Ma (n=21, MSWD=0.33) and 1848 ± 6
Ma (n=38, MSWD=0.46). Smaller populations also occur at ca. 2870, 2470, 2410, 2320, 2260, 2150,
1960, and 1640 Ma.
8.5.2 SAMPLE BH16
In sample BH16, 153 analyses were conducted on 81 zircon grains targeting four CL domains; convoluted and patchy cores, oscillatory zoning, weakly homogenous cores and rims (Figure 16a). A large, bimodal, concordant population exists between ca. 1800 Ma and ca. 1600 Ma, with smaller peaks occurring at ca. 2430, 2320 and 1840 Ma (Figure 16b). Singular concordant zircons also yield ages of 2003 ± 19 Ma and 2103 ± 18 Ma. A separate concordia (Figure 16c) and a combined probability density plot (Figure 16d) show that the two populations within the peak are distinct, covering intervals over ca. 1680-1620 Ma (n=87) and ca. 1760-1710 Ma (n=46). Concordant data from these peaks yield weighted average age estimates of 1652 ± 4 Ma (MSWD=0.51) and 1728 ± 6
Ma (MSWD=0.27) respectively. 28
8.5.4 SAMPLE I0508
In sample I0508, 104 analyses were conducted on 72 zircons, which targeted convoluted cores, homogenous cores, oscillatory zoning and rims (Figure 17a). When the data are displayed on a combined probability density plot (Figure 17b), the main population of zircon grains occurs in a broad peak from ca. 1680-1590 Ma (n=49) with a weighted average age estimate of 1625 ± 8 Ma
(MSWD=2.4). Smaller peaks yield ages of ca. 2640, 2570, 2490, 2420, 2330, 2140, and 1780 Ma, and one singular zircon yields an age of 2769 ± 17 Ma (Figure 17c).
9. IN SITU U-PB MONAZITE GEOCHRONOLOGY
9.1 Monazite grain morphologies
The textural location of the monazite grains is paramount for in situ monazite analysis. A detailed description of the internal and external grain morphologies and mineral relationships is included in
Table 9, and full summary of results is in Table 10 (Appendix II).
9.2.1 SAMPLE BH08 MONAZITE RESULTS
A weighted average of all analyses between 90-110% concordant yield an age estimate of 1573 ± 8
Ma (MSWD = 1.6; Figure 18a). The data are presented in accordance with the textural location of the monazite grains. Grains residing within G1 garnets yield weighted average age estimates of 1583 ± 9
Ma (MSWD = 0.18), grains located within G2 garnets yield weighted averages of 1564 ± 12 Ma
(MSWD= 0.62), and grains located within the sillimanite + orthoamphibole domains yield age estimates of 1567 ± 29 Ma (MSWD =3.9).
29
9.2.2 SAMPLE BH09 MONAZITE RESULTS
A weighted average age estimate of all monazite grains between 90-110% concordant yield an age estimate of 1560 ± 11 Ma (MSWD= 3.8; Figure 18b). Monazite grains located within G1 garnet grains yield a weighted average age estimate of 1587 ± 10 (MSWD=0.16), whereas those found within G2 grains produce a weighted average estimate of 1554 ± 15 Ma (MSWD=3). Grains found within the sillimanite-orthoamphibole domains cover spread of ages from 1560- 1389 Ma, which yield an average age of 1540 ± 32 Ma (MSWD= 5.6).
9.2.3 SAMPLE BH16 MONAZITE RESULTS
A concordant population exists between ca. 1660- 1600 Ma. A weighted average of all monazite grains concordant between 95-105 % produces an age estimate of 1607 ± 18 Ma (MSWD=3.1; Figure
18c). Monazite grains located within garnets yield weighted average estimates of 1607 ± 22 Ma
(MSWD=2.6), and those located in the matrix of K-feldspar, quartz or plagioclase yield statistically identical age estimates of 1606 ± 46 Ma (MSWD=4.8). A cluster of older monazite grains are also preserved between 1615-1684 Ma, which generate a weighted average of 1641 ± 15 Ma (MSWD=
1.6).
9.3.8 SAMPLE BH10 MONAZITE RESULTS
Nineteen of the 40 monazite analyses were concordant within 90-110%, with a concordant population at ca. 1600 Ma (Figure 19). A weighted average estimate of all concordant data yields an age of 1599
± 16 Ma (MSWD=1.6).
10. ZIRCON TRACE ELEMENT RESULTS
30
Table 11 contains all relevant information regarding ΣREE, LREE, HREE Ce/Ce* and Eu/Eu* for the
CL domains analysed within each sample. Information is displayed whereby LREE= Smn/Lan,
HREE= Lun/Smn, Ce/Ce* = Cen/√(Lan x Prn), Eu/Eu* = Eun/√(Smn x Gdn) (Taylor & McLennan
1985), where n signifies the element has been chondrite normalised.
BH17 shows very little variation between core and rim analyses (Figure 20a). BH15 shows a marked difference in ΣREES between cores and rims (~1345 & 829 ppm, respectively; Figure 20b). Overall
REE slopes of both samples are steep with moderate negative Eu anomalies (maximum Eu/Eu* = maximum 0.31) and moderate Ce anomalies (Ce/Ce* = maximum 13.97). A small number of rim analyses in both samples are characterised by LREE enrichment resulting in very flat REE signatures, negligible negative Eu anomalies (Eu/Eu*= maximum 0.31) and moderate Ce anomalies
(Ce/Ce*=maximum 11.71).
Zircon grains from the ca. 1750 and ca. 1650 Ma populations were targeted in metasedimentary samples BH08, BH16 and I0508. Cores within metasedimentary samples, BH08 and BH16 (Figures c, d), have moderate HREE slopes (Lun/Smn =4-57, Avg=24.45 and Lun/Smn = 10-59, Avg=30.62 respectively), decreased negative Eu anomalies (Eu/Eu*=maximum 0.13) and reduced Ce anomalies
(Ce/Ce*= maximum 3.81). REE patterns for rims are virtually identical in BH08 and BH16, with the exception of three analyses that are particularly HREE depleted and LREE enriched (HREE =3 – 4.3,
Avg=3.9).
REE patterns from I0508 are very different to the other samples (Figure 20e). Core analyses show
REE patterns that are variably enriched in LREE (La-Pr= 101-103) and show relatively flat signatures.
A minor Ce anomaly is present (Ce/Ce*= 0.92-1.7, avg=1.2) as well as a negative Eu anomaly
(Eu/Eu*= 0.05-0.93, avg=0.48). Rims are typified by shallow HREE slopes (Lun/Smn =0.45-5.9,
Avg=2.8) with extremely reduced Ce anomalies (Ce/Ce*=0.82-1.36, avg=1.16). 31
11. TI-IN-THERMOMETRY TEMPERATURE ESTIMATES
The temperature results for all analyses are displayed in Table 11a-e (in Appendix I) and Figure 21.
Approximately 22% of analyses were removed as erroneous outliers. BSE and CL imaging reveals that the areas targeted in these analyses were located on zircons with cracks, or were near micro- inclusions (dark, ~1-5 μm). High Ti has been documented along the surface of cracks within zircon
(Harrison & Schmitt 2007; Hofmann et al. 2009) often as a result of secondary zircon precipitated during thermal disturbance. It is possible that the inclusions in zircons are of a titanium bearing mineral, such as ilmenite, present in all the metasediments. Ablations taken near these areas produce spuriously high crystallisation temperatures. In this study the individual analyses removed yield deceptive temperatures between ~1100-2500°.
A single zircon grain at ca. 1673 Ma contains 111 ± 20 ppm Ti; corresponding to a temperature of
1036 ± 48 °C. Metamorphic zircon grains from the ca. 1740 Ma peak in sample BH08 contain average Ti contents of 30 ± 20 ppm, corresponding to average temperatures of 924 ± 89°C.
Convoluted and homogenous detrital cores from the ca. 1850 Ma peak contain average Ti contents of
56 ± 21 ppm, which correspond to a weighted average temperature of 980 ± 69°C. In sample BH16 metamorphic zircon of the ca. 1640 Ma contain average Ti contents of 48 ± 12 ppm, generating a weighted average crystallisation temperature of 935 ± 55° C. Metamorphic zircon from the ca. 1740
Ma peak contain similar average Ti contents (41 ± 15 ppm), consequently yielding temperatures of
932 ± 69° C. Metamorphic zircon from the ca. 1640 Ma in sample I0508 contain average Ti contents of 39 ± 10 ppm, yielding average temperatures 937 ± 38°C.
Zircons from meta-igneous samples (BH15 and BH17) yield overall lower temperatures. Cores
(oscillatory-zoned and convoluted) and rims from BH15 produce statistically indistinguishable temperatures of 824C° ± 18°C and 830C° ± 20°C respectively. Cores and rims from BH17 produce slightly higher temperature estimates of 850C° ± 26°Cand 842C° ± 29°C. 32
12. LU-HF RESULTS
Lu-Hf isotope compositions were determined for sixty one zircon grains for three samples (BH08,
BH16 and I0508). The Lu-Hf isotope compositions for the metasedimentary zircons are shown in
Table 12 organised by sample number, and ordered by 207Pb/206Pb crystallisation age. The grains analysed cover a spread of U-Pb ages between ca. 2868 and 1575 Ma. As a group, the zircon grains have present-day Hf isotopic compositions ranging from 0.280898 to 0.281757 (Figure 22a). This corresponds to a variable range of epsilon hafnium (εHf) values that range from -18.01 to +10, with the largest εHf populations occurring at ca. -2 and -6. Crustal model ages (TDM) were calculated for each zircon assuming average continental crust with 176Lu/177Hf values of 0.0015 (Griffin et al. 2008) as the zircon grain growth reservoir. Based on this crustal model, a broad age range of ca. 3.5-2.3 Ga is obtained for the Ongole Domain metasediments. There are no apparent relationships between the samples, and therefore the data is presented and analysed in accordance with the zircon crystallisation age. Figure 22b displays εHf vs. the U-Pb crystallisation age for zircon grains in samples BH08, BH16 and I0508.
The eldest zircon grains analysed have 207Pb/206Pb crystallisation ages of ca. 2769 and ca. 2868 Ma.
The zircon grains yield εHf values of -5 and -1, and TDM of 3.4 and 3.5 Ga, respectively. Two grains at ca. 2640 Ma yield εHf values of -2 and +12, and TDM of 3.2 or 2.3 Ga respectively. At ca. 2550 Ma, zircon grains have negative εHf values between -4 and -6 (average= -5), and TDM of ca. 3.3 Ga.
Zircon grains aged ca. 2500 to 2400 Ma yield εHf values between -7 and +4 (average= -3), and TDM between 2.8 and 3.4 Ga (average= 3.2 Ga). Two discrete populations are evident within the ca. 2350-
2300 Ma peak; one with εHf between -12 to -7 (average= -10) and TDM of ca. 3.4 Ga, and the second with εHf -2 and -1 and TDM of ca. 3 Ga.
Grains with ca.2280-2200 Ma ages yield a broad spectrum of εHf values between -18 to +7.53
(average= -5.6), and TDM between 2.7 and 3.9 Ga (average= 3.1 Ga). Grains with ca. 2100 Ma ages 33
yield εHf values of -11 to -6 (average= -8) and TDM between 3.1-3.4 Ga (average= 3.2 Ga). Zircon grains within the ca. 2150 Ma peak yield positive εHf values between -1 and +4 (average= +2) with corresponding TDM between 2.5-2.8 Ga (average=2.6).
Zircon grains at ca. 1950-1850 Ma have εHf between -9 and +1 (average= -5), and TDM varying between 2.6 and 3 Ga (average= 2.8 Ga). The youngest grains analysed are from ca. 1750-1600 Ma interval. These grains generate negative epsilon values between -10 and -1 (average= -4), and TDM of
2.4-2.9 Ga (average= 2.6 Ga).
13. INTERPRETATION OF RESULTS
13.1 Interpretation of zircon data: U-Pb and REES
The focus in many geochronology studies, including this study, is to integrate U-Pb, Lu-Hf and trace element data to constrain both the conditions of petrogenesis and the timing of grain crystallisation
(Yuan et al. 2008; Chen et al. 2010). Zircon grains extracted from metaigneous and metasedimentary rocks consistently preserve evidence for complex isotopic disturbance. Magmatic zircon typically exhibits well developed growth zoning (oscillatory zoning); a feature that reflects compositional variation of Zr, Si and trace amounts of Hf, P, Y, REE, U and Th (Corfu et al. 2003). Zircon grains in all samples invariably preserve some growth zoning, but it is always disturbed, blurred, or truncated by homogenous weakly to strongly luminescent fronts; features commonly attributed to overprinting during high grade metamorphism (Hoskin & Black 2000; Hoskin & Schaltegger 2003; Hofmann et al., 2009; Flowers et al. 2010), or disturbance within the zircon crystal during the final stages of magmatic cooling (Harley & Black 1997; Corfu et al. 2003; Pidgeon et al. 1998)
The ratio of Th to U in zircon is used as a guide for differentiating between magmatic and metamorphic zircon (Harley & Black 1997; Pidgeon et al., 1998; Rubatto et al. 2001; Rubatto 2002;
Corfu F. et al. 2003). The term ‗metamorphic zircon‘ is used in this study in the style of Martin et al., 34
(2008), whereby it refers to zircon that grew during metamorphism, or a previously existing zircon that equilibrated (partially or completely) during metamorphism. Empirically, felsic igneous rocks typically yield zircon grains with average Th/U ratios of >0.5 (Xiang et al. 2011); whereas metamorphic zircon will preferentially purge larger Th cations during a recrystallisation event, resulting in Th/U ratio of <0.2 (Hoskin & Schaltegger 2003; Rubatto 2002; Schaltegger et al. 1999).
Adhering to these assumptions, zircon grains extracted from metaigneous rocks are predominantly
‗magmatic‘ (Figures 22a, b). In the metasedimentary zircon grains from the dominant ca. 1750 Ma and 1650 Ma peaks, the Th/U ratio is characteristically low (<0.2), lending support to the growth of metamorphic zircon over this period (Figures 22 c, d). However, modification of the Th/U ratio does not always accompany metamorphism (Bomparola et al. 2007) and is sometimes only partially complete. This can result in a linear trend of analyses that plot down towards a Th/U ratio of <0.2 as the process takes place (e.g. Figures 22 c, d).
REE patterns preserved in metaigneous zircons are distinct (Figures 20a, b), and provide insight into the conditions present during petrogenesis. Zircon grains in BH 15 and BH17 have Ce anomalies (in cores and rims) that are lower (~1-13) than the averages described for felsic rocks in Hoskin and
Schaltegger (1999); where Ce anomalies range between 39-132 for charnockites, diorites, aplites and dacites. The magnitude of the Ce anomaly is governed to the abundance of Ce4+ in melt; which is a function of oxygen fugacity (Hoskin & Schaltegger 2003). Ballard et al. (2002) demonstrates a relationship between Ce, U-Pb age, oxygen fugacity and fractional crystallisation in igneous suites, whereby felsic end members were found to have increased Ce anomalies in oxidised magmatic states.
If the relationship between oxidation state and crystallisation is sound, this could possibly account for the reduced Ce anomalies seen in BH15 and 17. Moderate Eu anomalies in BH17 (~0.31) indicate zircon crystallisation following or coexisting with feldspar crystallisation (Hoskin & Ireland 2000;
Ballard et al., 2002; Rubatto 2002), whereas lower negative Eu anomalies in BH15 suggest that crystallisation occurred prior to, or during early feldspar crystallisation, or alternatively in an ‗open‘ reservoir. In this situation there is an infinite supply of trace elements, i.e. the melt present in the rock 35
(Rubatto et al., 2001). An overall inconsistency in REE patterns in the igneous samples can also be attributed to chemical variation and disequilibrium in zoning at a microscopic scale (Schaltegger et al., 1999).
REE composition from zircon grains in garnet bearing, metamorphic rocks can be used to link paragenesis to the timing and conditions of metamorphism (Rubatto et al., 2001; Rubatto 2002;
Hanchar & van Westrenen 2007). In a closed system, coexisting zircon and garnet will compete for
HREE as the trace element reservoir is limited; consequently, metamorphic zircon will yield HREE depleted patterns (Rubatto 2002). A small number of rim analyses in BH16 fit this pattern (Figure
20d), indicating possible metamorphic zircon growth with garnet porphyroblasts at ca. 1660 Ma (ages of zircon are ca. 1669, 1667 and 1650 Ma). However, the majority of rim analyses in garnet bearing samples (BH16 and BH08) are not HREE depleted, which can be interpreted in a number of ways.
Zircon growth may have occurred prior to garnet growth, which in a closed system would deplete the trace element reservoir for subsequent garnet growth. Alternatively, the rims could have grown in an open system, where garnet can coexist with zircon and utilise an infinite reservoir of elements; preventing any compositional changes in zircon (WU 2004). Overall, REE patterns in the ca. 1750 and 1650 Ma populations are quite flat, yielding similar patterns to metamorphic zircon described by
Whitehouse (2000).
LREE enrichment is recognised in a number of metaigneous and metasedimentary zircon grains
(Figures 20a-d), and in all zircon grains from sample I0508. LREEs are generally incompatible within the zircon structure, due to a larger ionic radius by comparison to HREEs (Bomparola et al., 2007).
However, the behaviour of LREE in zircons is largely unknown, and is conservatively attributed in this study to a number of scenarios. LREE enrichment in metamorphic zircon grains from sample
I0508 and BH16 is interpreted to result from increased Th and U contents (Th=~739 ppm; U =~2306 ppm); which are much higher than the average described for metasedimentary granulite zircons
(Th=~6-177ppm, U=~41-1393 ppm; Rubatto 2002). Zircon grains with high Th and U contents are vulnerable to radiation damage, which distorts the crystal structure, and allows for the 36 accommodation of larger LREES (WU 2004). Minute inclusions of LREE bearing minerals (i.e. monazite, allanite) could have been sampled during ablation, resulting in erroneous REE patterns (Wu
& Zheng 2004). However, if LREE bearing micro-inclusions were unintentionally analysed, anomalously high Th contents up to ~75000 ppm would be present in the zircon data (Hurai et al.
2010). Alternatively, zircon that crystallises, or re-equilibrates with coexisting pyroxene can exhibit
LREE enriched patterns, as pyroxene will preferentially extract HREE out of the melt. The effect of this is an overall flatter REE pattern (Nemchin et al. 2010), which could explain LREE enriched zircon in the pyroxene bearing metagranites (BH15 and BH17).
The broad range of U-Pb ages along concordia in all samples analysed is a likely consequence of metamorphism, synchronous with, or following the emplacement of the igneous protoliths.
Petrologically, a number of mechanisms could have attributed to the broad spectrum of ages including, solid-state recrystallisation (Corfu et al. 2003; Hoskin & Schaltegger 2003), coupled- dissolution reprecipitation (Geisler et al. 2007), zircon growth at the onset of anatexis (e.g. Roberts &
Finger 1997), or zircon growth resulting from the breakdown of zirconium bearing minerals such as ilmenite and garnet (Fraser et al. 1997; Degeling et al. 2001; Geisler et al., 2007). The onset of melting in granulite-facies rocks promotes zircon growth via Ostwald ripening; a process where the coarsening of larger grains occurs at the expense (dissolution and precipitation) of smaller grains
(Peck et al. 2010). Closed system, solid state recrystallisation has been shown to produce blurred primary zones, patchy zoning, and ―ghost‖ zoning in granulite-facies zircon crystals (Tichomirowa et al. 2005); internal features seen frequently within the OD zircon grains (see Table 7). Some evidence was noted for coupled-dissolution reprecipitation (BH08, BH16); whereby zircon preserves a
‗spongy‘, porous texture within re-equilibrated crystal (e.g. Fig. 1 in Geisler et al. 2007).
The resolution of the CL images and depth of geochemical analysis indicate that it is not feasible to define a single mechanism of disturbance in the zircon grains. In reality, the processes described are end members, thus it is entirely possible a combination of all occurred. On the basis of CL image 37 analysis, the preferred interpretation is solid-state recrystallisation, coupled with metamorphic zircon growth as rims and featureless grains. Heterogeneous lead loss has been previously documented in solid-state recrystallised granulite facies zircon grains (Flowers et al., 2010; Kryza et al. 2011; Wan et al. 2011), and provides an explanation for inverse ages frequently seen between rims and cores (e.g.
BH12 spot 5 & 6).
The effects of recrystallisation appear to have been far more pervasive in the meta-sedimentary zircons than the meta-igneous grains. This is attributed to the extensive pre-metamorphic history experienced by the detrital zircon grains. Zircon grains that reside below the ‗critical amorphous temperature‘ (<350°C) will accumulate radiation damage in the crystal lattice over extended periods of time (Meldrum et al. 1998). In this study, detrital zircons were potentially exposed at the surface for up to 1 Ga before undergoing granulite-facies metamorphism; therefore it is entirely possible a number of detrital grains became metamict in the process of erosion and deposition. By comparison, the meta-igneous grains were wholly intact, prismatic grains that are more resistive to tectonothermal disturbance. What is evident from the zircon data is the presence of at least one metamorphic event, represented by the youngest concordant metamorphic zircon population at ca. 1590 Ma. However, the dominance of metamorphic zircon at ca. 1640 Ma suggests a growth event at this age, or alternatively ongoing metamorphism spanning a period from ca. 1640-1590 Ma.
13.2 Interpretation of monazite data
At granulite-facies conditions, monazite grains record an age along the metamorphic P-T path
(Rubatto et al., 2001). Collectively, all monazite grains in samples BH08, BH09 and BH16 yield a weighted average age of 1590 ± 8 Ma. In Domain 2, sample BH16 preserves the oldest monazite grains found in this study, with grains up to 1684 ± 19 Ma armoured within equant, coarse grained garnets. The majority of the monazite grains hosted within garnets and the matrix are uniformly ca.
1600 Ma. In Domain 1, sample BH08 and BH09 monazite grains located within G1 grains generate 38 ages of ca. 1590 Ma, which are comparatively older than those found in G2 grains and sillimanite- orthoamphibole zones.
The preservation of older monazite grains within the garnet porphyroblasts has been previously documented and can be credited to a number of scenarios. Firstly, it is possible the Th-U-Pb systems of the monazite grains armoured within a number of BH16 garnets, were protected against tectonothermal disturbance (Montel et al. 2000; Forbes et al. 2007). Similar to zircon, the closure temperature of monazites is high (> 900°C) and Pb diffusion is extremely slow, meaning that solid state recrystallisation is highly improbable (Cherniak et al. 2004). Therefore, a plausible explanation for comparatively younger monazite populations within the matrix is exposure to recrystallisation via fluid mediated, coupled dissolution-reprecipitation processes (Simmat & Raith 2008; Williams et al.
2011).
The crystallisation of the younger grains could also be a direct consequence of the chemistry of the rock and the changing pressure-temperature conditions during metamorphism. Using calculated phase diagrams, Kelsey et al. (2008) demonstrates that monazite and zircon grains will behave differently under increasing metamorphic conditions. At temperatures above ~700-780°C in monazite saturated rocks, where melt loss does not occur; monazite will dissolve completely and will recrystallise upon cooling below the solidus. Therefore, the younger monazite grains could represent melt crystallisation as the rocks passed through lower temperatures of ~780-700°C. Many of the grains embody irregular shapes and complex internal textures, indicative of recrystallisation in the presence of a hydrous phase
(Vavra & Schaltegger 1999).
13. DISCUSSION
13.1 Provenance of meta-sedimentary protolith rocks
13.1.1 TIMING OF DEPOSITION AND SOURCE CHARACTERISTICS
39
High grade metamorphism and deformation in the Ongole Domain, means that sedimentary features relating to paleoflow (i.e. ripples, cross-bedding) are destroyed. The paucity of outcrop also means that there is no direct information to prove that the metasedimentary rocks are part of the same sedimentary succession. However, the similarities between the detrital zircon-age spectra suggest broadly similar sources were involved in the derivation of the sedimentary protolith rocks (Payne et al. 2006b). This study is careful to avoid the assumption that quantitative population of the detrital zircons in the metasedimentary rocks are an accurate representation of the natural distribution; and hence natural source terrains (Anderson 2005). The statistical likelihood of error is greatly increased when interpreting provenance data using only the zircon crystallisation age (Howard et al. 2009).
However, the application of Lu-Hf data as a ‗geochemical tracer‘, in conjunction with U-Pb zircon ages, will decrease the risk of error (Anderson 2005).
The maximum age of deposition is tentatively placed at the appearance of the youngest detrital zircon grain. Spot 21_74 in sample BH08, preserves a clearly defined, oscillatory-zoned core (1847 ± 20
Ma), which is part of a unimodal population at ca. 1845 Ma; interpreted to represent the dominant detrital peak seen within the Ongole Domain.
Although there is quite conclusive evidence for metamorphism at ca. 1640-1590 Ma (e.g this study;
Simmat & Raith 2008; Upadhyay. D. 2009), the minimum age of deposition is conservatively set at ca. 1750 Ma. Many of the zircon grains in the ca. 1750 Ma population preserve evidence for being metamorphic in origin; exhibiting consistently low Th/U ratios and flat REE patterns (Figure 20,
Figure 23), blurred or featureless CL, and often encompass large (>20 μm) overgrowths on older detrital grains. The present day 176Hf/177Hf values of the ca. 1750 - 1650 Ma zircon grains cluster tightly around ~28175, and yield εHf values of -7 to -1. As the zircon grains are interpreted as metamorphically grown or altered, the data is handled with caution. Partial dissolution of zircon releases Hf into the melt, which can then mix with radiogenic matrix Hf, and eventually be taken up by new or re-equilibrating zircon during melt crystallisation (Gerdes & Zeh 2009). Thus, it is possible the isotopic composition of the zircon reflects a mixture of Hf from the matrix and the older protolith 40 zircon. The ca. 1750 Ma age is in agreement with a metamorphic event recently proposed at 1760 Ma
(Bose et al., 2011).
Using these constraints the Ongole Domain sediments are interpreted to have been deposited between ca. 1850-1750 Ma. The isotopic composition of detrital grains aged between ca. 2900-2550 Ma (TDM
= ca. 3.2 Ga, εHf= -5 to 0), invariably indicates reworking of Mesoarchaean crust with juvenile melts.
Zircon grains between ca. 2100-2300 Ma are interpreted to have been derived from evolved source regions; with most zircon grains recording variable crustal mixing (εHf= -18 to -1), and a uniform
TDM of ca. 3 Ga.
On the basis of mineralogy and bulk chemistry (Table 5), the protolith to BH08 and BH09 is interpreted to have been a fine grained clastic clay, mud or siltstone (Winter 2010); whereas the protolith rocks for BH16 and I0508 are interpreted to be an arkosic sediment and an impure sandstone, respectively (Winter 2010).
13.1.2 PROVENANCE TERRAINS FOR THE ONGOLE DOMAIN META-SEDIMENTARY
ROCKS
Prevailing continental reconstruction models of Nuna (Columbia) loosely constrain the location of
India; and by default the Krishna Province, during the Paleoproterozoic and Mesoproterozoic. The time over which Nuna amalgamated is contested, but is generally considered to have been between ca.
2100-1800 Ma (Zhao et al., 2004; Hou et al., 2008; Evans & Mitchell 2011); subsequently rifting over a long period between 1700-1300 Ma (Ernst et al. 2008; Evans & Mitchell 2011). Recent reconstruction models place proto-India in three discrete geographic locations: 1) juxtaposed against the Napier Complex (NC) and East Antarctica (EA) and the North China Craton (NCC) (Zhao et al.,
2002; Zhao et al., 2004) at ca.1.85 Ga; 2) adjacent to Madagascar, coastal EA, Australia and
Laurentia (LA) at ca.1.5 Ga (Rogers & Santosh 2002); 3) adjacent to the NCC and Laurentia (Hou et 41 al., 2008); and 4) against the NC and the Yilgarn Craton (YC). Using these models as a guide, a time- space plot has been constructed showing all major zircon forming events and the tectonic evolution of the potential source terranes throughout the late Archean to Neoproterozoic (Figure 24).
Deposition of the OD protolith sedimentary rocks has been suggested to have occurred along the western margin of the eastern Dharwar Craton (DC) (Dobmeier 2003; Mukhopadhyay & Basak
2009); and have been further interpreted as lateral equivalents of the Cuddapah Supergroup (Rickers et al., 2001; Dobmeier 2003). Isotopic constraints and LA-ICP-MS U-Pb zircon studies covering the lower Cuddapah Supergroup provide evidence for detrital provenance being from sourced predominantly from within the DC (Figure 25; Alexander 2011; Falster 2011; Gore 2011). The OD metasedimentary rocks lack the dominant ca. 2500 Ma detrital peak evident in the lower Cuddapah
Supergroup rocks that is such a characteristic component of the DC. Zircon grains from the ca. 2500
Ma DC peak yield highly variable εHf values between -15 and +5 (Alexander 2011; Falster 2011;
Gore 2011) with TDM ca. 3 Ga; broad constraints that are somewhat comparable to the one ca. 2500
Ma grain analysed for Lu-Hf isotopes within the OD ( Spot 8_26, εHf=+4, TDM=2.7). However, the absence of ca. 2500 Ma grains is not used as direct evidence to suggest sediments were not derived from the DC, as sample bias during detrital zircon selection could have unintentionally missed the population of ca. 2500 Ma grains (Pieter 2004); or the ca. 2500 Ma rocks may have structurally or stratigraphically obscured during sedimentation.
A Mesoarchean to Paleoproterozoic source terrain is required to account for the detrital peaks between ca. 2900- 2100 Ma. On the basis of U-Pb data alone, EA, the NCC, the North Australian
Craton (NAC) and the DC are characterised by zircon forming events of comparable ages to most of the detrital peaks in the OD, which are summarised in Table 13. The GC, LA, YC and Madagascar do not fit as source terranes in all instances (Figure 24). Lu-Hf zircon data is accessible across the GC
(Belousova et al. 2009; Howard et al., 2009; Howard et al. 2011), and to a lesser degree throughout
LA (Whitmeyer & Karlstrom 2007; Bickford et al. 2008). Whole rock Nd isotope data is available as an alternative tool for comparison across the DC (Pandey et al. 1995; Zachariah et al. 1995; Pandey et 42 al. 1997; Anand et al. 2003), (Zhao & McCulloch 1995; Giles et al. 2004) and YC (Nutman et al.
1993; Champion & Sheraton 1997). Comparison of εHf data obtained in this study with existing εNd data is possible using the calculations determined for the terrestrial Hf-Nd array (εHf =1.36 εNd +2.95) by Vervoort et al. (1999).
Taking into account the distribution of εHf values obtained from detrital zircon grains; potential source regions within the GC and LA are conservatively excluded as likely provenance terranes on the basis of isotopic evidence (Whitmeyer & Karlstrom 2007; Bickford et al., 2008; Belousova et al., 2009;
Howard et al., 2009; Howard et al., 2011). In general, these domains generate Mesoarchean to
Paleoproterozoic zircon grains that are too juvenile (LA), or quite evolved (GC), and yield young TDM
(< 2.3 Ga).
The dominant peak at ca. 1850 Ma is a particularly prolific period for global zircon generation, making it impractical to conclusively assign source regions (Condie et al. 2009; Condie & Aster
2010). Zircon forming events (Figure 24; Table 13) are documented in the proximal Vinjamuru
Domain (Vasuden 2003), the Cuddapah Basin (Murthy 1987; Bhaskar Rao 1995; Chatterjee &
Bhattacharji 2001; Anand et al., 2003), Mt Riiser- Larsen and the Howard Hills (EA) (Lanyon et al.
1993; Ishizuka 2008), and the NAC (Drüppel et al. 2009). Two ca. 1850 Ma metamorphic rims on a
2260 Ma and 1950 Ma detrital grain (BH08 spot 15, 108); can only be matched to metamorphic events in Enderby Land (EA) and the NAC (Figure 24).
Based on the limited results obtained during this study, it is considered unlikely that the Ongole
Domain metasedimentary rocks are the lateral, metamorphosed equivalents of the Cuddapah
Supergroup. The lack of zircon bearing source rocks in the DC for the ca. 2870, 1950-2050 Ma peaks, implies that sedimentation was not primarily derived from the DC. When considering the U-Pb zircon data alone, EA is considered the closest match to nearly all of the detrital peaks found within the
Ongole Domain, but the NAC and the NCC cannot be discounted. In accordance with these observations, the present study finds support for the Zhao et al. (2004) reconstruction model for Nuna 43
(Columbia) at 2100-1850 Ma; which juxtaposes Antarctica, North Australia and India (Figure 26).
Figure 26 postulates the configuration of Nuna at ca. 1850 Ma, just prior to deposition of the Ongole
Domain sedimentary rocks; allowing the visualisation of possible sedimentary pathways prior to collisional orogenesis at ca. 1650 Ma.
13.2 The timing and conditions of crystallisation for the metaigneous rocks
The data presented here indicates that the igneous intrusives do not preserve a simple correlation between isotopic data and age. The wide scatter along concordia within each sample, coupled with irregular trace-element patterns, is attributed to partial to complete resetting within the zircon crystals
(Bomparola et al., 2007). Consequently, careful evaluation of the internal textures and trace element chemistry must be conducted prior to the assignment of a protolith rock crystallisation age.
Collectively, meta-igneous zircon grains yield low Ce anomalies (~1-13), variable LREE enrichment, and a wide range of Th, U and Y values (Table 10). Similar patterns are preserved in reset zircon grains from the Deep Freeze Range in Antarctica (Bomparola et al., 2007). The unconventional distribution of trace elements within the zircon is interpreted to reflect considerable mobility of these elements during solid-state diffusion, in the presence of deformation and ongoing plutonism
(Bomparola et al., 2007); analogous to the conditions described in the Ongole Domain (Dobmeier
2003; Simmat & Raith 2008).
Ti-in-zircon thermometry provides an estimate for the crystallisation temperatures of the charnockites; yielding much higher temperatures than the averages described for felsic (653 +/-124°C) and mafic
(758 +/-111°C) rocks (Fu et al. 2008). The weighted average temperature estimates vary only slightly between 840-820°C for cores and rims (Figure 21); but is within the documented crystallisation range for charnockites (650-950°C) based on pyroxene thermometry (Weiss & Troll 1989; Frost et al.
2000). Therefore, the temperatures calculated in this study are reasonable for charnockites. 44
The most accurate estimate for the maximum crystallisation ages for the meta-igneous rocks is calculated using the weighted average ages of the oldest, concordant populations in each sample (e.g
Miller et al. 2006). Domain 1 experienced temporally, overlapping intrusions spanning ca. 1639-1578
Ma (Figure 27). In general, younger meta-granites tend to preserve weaker, inconsistent fabrics and anatomising networks of undeformed K-feldspar and quartz rich leucosomes (Figure 5h); giving the impression that fabric defining deformation was concentrated earlier in the ca. 1640-1620 Ma period.
13.4 Nature of metamorphism
A P-T pseudosection calculated using the bulk rock chemistry for sample BH16 (peak assemblage of orthopyroxene + garnet + k-feldspar + plagioclase + ilmenite), constrains the pressure and temperature of peak metamorphism to UHT conditions of ~910°C and pressures up to 9.1 kbar. Ti-in- zircon thermometry conducted on interpreted metamorphic rims from the rock independently supports the UHT conditions; estimating temperatures of 935 ± 55° C.
The post-peak evolution of sample BH16 can be conservatively interpreted on the basis of minor retrograde reaction textures. The presence of biotite around the rims of garnet and opx grains is attributed to retrogression, where garnet and orthopyroxene are consumed at the expense of biotite
(Bento dos Santos et al. 2011). The reaction could represent the rock cooling below ~800°C following peak metamorphism, which on Figure 9 would suggest the rock passed through the biotite- orthopyroxene-garnet-K-feldspar-quartz stability field.
Sample BH08 (and BH09) are heterogeneous at a microscopic scale and preserve sub-assemblages that developed primarily at the expense of garnet in the first instance, and then subsequently cordierite. Using a calculated pseudosection from Diener et al. (2008) an interpretation of the P-T evolution can be made, for comparison to the conditions calculated for BH16 (Figure 28). Although the pseudosection is not generated for the specific bulk compositions associated with BH08 and BH09 45
(Table 5), it is sufficient for a simplified interpretation, as it depicts the generalised phase relations for a high-T aluminous rock with an intermediate Fe-Mg ratio.
The peak metamorphic assemblage is interpreted to be garnet (G1) + sillimanite + ilmenite + magnetite + K-feldspar + quartz, which are stable at high temperatures similar to that calculated for
BH16. Based on the phase relations depicted in Figure 28, the growth of cordierite in the presence of garnet-sillimanite suggests decompression at comparatively high temperatures. Coinciding with this reaction, is the growth of secondary garnet (G2), which frequently forms intricate, symplectic intergrowths with ilmenite/magnetite on the margins of earlier G1 garnet. As garnet-sillimanite are in contact elsewhere in the sample, it is suggested the formation of cordierite was associated with adjustment of garnet-sillimanite modes, rather than the termination of the garnet-sillimanite association. The development of the orthoamphibole-bearing assemblage at the expense of cordierite is consistent with a cooling dominated P-T trajectory at mid-crustal levels (Figure 28). The peak metamorphic conditions interpreted for BH08/09 (Domain 1) are somewhat comparable to the calculated conditions for sample BH16 (Domain 2); but the rocks do not preserve conclusive evidence for similar retrograde conditions.
The HT-UHT conditions calculated by this study, strongly poses the question, what processes drive such high temperatures during collisional orogenesis? Under UHT conditions the crust has achieved an advective geothermal gradient steeper than ~20°C per km (Brown 2007). There is currently no consensus on the heat source that drives UHT metamorphism, but three sources are commonly proposed in continental collisional systems (Clark et al. 2011). They are: increased mantle heat flow in weak, thin back arc basins; mechanical heating in ductile shear zones; and, elevated radioactive heat production in a thickened crust.
Although the development of a back arc basin in the Krishna Province has been postulated at ca. 1.85
Ga (Vijaya Kumar et al., 2011), this is unlikely to have attributed to UHT conditions due its existence approximately 200 myr prior to orogenesis. Mechanical heating is considered negligible at high 46 temperatures, and thus is unlikely to have attributed. The EGB granulites are particularly enriched in heat producing elements (Kumar 2008), which are postulated as a critical component for generating
UHT conditions (Clark et al., 2011), and may have played a contributing role.
Alternatively, Santosh & Kusky (2009) propose that ridge subduction is a geodynamic scenario that would potentially allow for the preservation of UHT rocks in the arc and forearc of a subduction zone; aiding in the generation of relatively dry, granulite facies assemblages in a regime that is normally characterised by a low-T, subduction zone geotherm. As active margin tectonics preceded continent-continent collision in the Ongole Domain, this is a setting that must be considered.
13.3 Polyphase metamorphism in the Ongole Domain?
Constraining the timescale over which a UHT metamorphic event occurred is problematic (Kelsey
2008). Zircon and monazite are widely used to place temporal constraints on metamorphism; however at temperatures > 900°C they are vulnerable to diffusion (Rubatto et al. 2001), and data must be interpreted with caution. A large zircon peak at ca. 1750 Ma is tentatively interpreted as metamorphic on the basis of distinct CL characteristics and elemental chemistry. However, further geochronological and metamorphic analysis is needed to confirm that the event occurred insitu.
The combined metamorphic geochronological data generate a large, bimodal population, with monazite growth peaking at ca. 1590 Ma, and metamorphic zircon in the same rocks, generating a broad range along concordia from ca. 1660 to 1580 Ma, with a dominant peak of ca. 1640 Ma. The data can be construed in one of two ways: 1) several, discrete metamorphic events occurred within the
Ongole Domain between ca. 1660 Ma and 1570 Ma; or, 2) a single, prolonged, granulite facies event covering ca. 1660-1570 Ma. To validate either hypothesis, the ~50 myr gap between the dominant zircon and monazite populations must be addressed.
47
The oldest group of monazite grains encountered (ca. 1640 Ma) are armoured within garnets in sample BH16. HREE depleted rims from the dominant ca. 1640 Ma population (Figure 20d) are proposed as evidence to support synchronous growth of zircon and garnet in Domain 2 (Rubatto 2002;
Hanchar & van Westrenen 2007). The ca. 1640 Ma peak is not recorded in monazite grains in Domain
1, but is recorded in zircon grains. Petrologically, the monazite grains hosted within G1 and G2 garnets are considered more vulnerable to disturbance. The grains are heavily fractured, which would allow for fluid infiltration and subsequent monazite recrystallisation in the gaps between coarse grains; a feature commonly seen in samples BH08/09. If several discrete events occurred in the
Ongole Domain, the second event is interpreted to have occurred at ca. 1590 Ma. As discussed, this event is interpreted to have caused complete recrystallisation of monazite grains in Domain 1, and partial recrystallisation of monazite grains in Domain 2. However, the event is recorded in both domains in the zircon grains. Isotopic disturbance and partial recrystallisation within protolith zircon grains, is interpreted to have caused a ‗smear‘ of U-Pb data along the concordia towards ca. 1590 Ma
(e.g. Moller et al. 2003).
Making the assumption that monazite grains hosted within retrograde textures (samples BH08/09) crystallised during the formation of the reactions, a tentative temporal interpretation of the ca. 1590
Ma event can be considered (e.g. Bhandari et al. 2011). Monazites preserved within garnet grains
(G1) plot between ca. 1600-1580 Ma, implying the peak mineral assemblage crystallised prior to ca.
1580 Ma. Monazite growth hosted within G2 grains are aged between ca. 1600-1470 Ma, comparable to those located within the cordierite garnet + sillimanite + orthoamphibole reaction, which fall between ca. 1590-1390 Ma. The overlap between the texturally distinct monazite groups implies that the retrograde reactions occurred quite rapidly. This interpretation suggests that the ca. 1590 Ma monazite peak is likely to reflect the post-peak period along the P-T path, prior to the Domain 1 rocks undergoing high-T decompression and cooling at mid crustal levels after ca. 1580 Ma (Foster et al.
2004; Diener et al., 2008; Bhowmik et al. 2011). This is conservatively interpreted to suggest that the presence of fluids was simultaneous with retrogression, as monazite requires the mobilisation of fluid to recrystallise following metamorphic climax (Ayers et al. 2003; Tartèse et al. 2011). 48
Evidence for an ongoing metamorphic event from ca. 1640-1590 Ma is somewhat equivocal.
Continual or intermittent zircon growth over extended metamorphic events has been previously documented (Ashwal et al. 1999; Bomparola et al., 2007; Claoué-Long et al. 2008; Högdahl et al.
2011). Similarly, monazite in poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages in the evolution of an orogen (Högdahl et al., 2011). Hence, the oldest monazite inclusions could thus record growth along the prograde path of a long, hot orogen (Melleton et al.
2009), and the younger grains along the retrograde path.
The presence of additional sources of heat and/or heat transport, such as the emplacement of magmatic bodies or the advection of metamorphic fluids; can also contribute thermal pulses to mountain building cycles, and result in heterogeneous crystallisation ages in zircon and monazite
(Ague & Baxter 2007; Lancaster et al. 2008). Magmatic intrusions were emplaced in the Ongole
Domain spanning a broad period of time from ca. 1640-1570 Ma (this study). The igneous bodies potentially provided an intermittent source of advective heat and fluids, which may have encouraged continual zircon growth over a ~50 myr period (Ashwal et al., 1999). Episodic resetting of monazite grains was possibly encouraged by the release of volatiles (CO2, H2O) during late stage crystallisation, as monazite is particularly susceptible to disturbance in the presence of fluids
(Williams et al., 2011). Zircon is more resistant to hydrothermal disturbance (Tartèse et al., 2011); however, new growth is often encouraged in the presence of fluid (Zheng et al. 2007).
Unfortunately, the imprecision of the LA-ICP-MS technique; and the effect of UHT metamorphism, mean it is implausible to definitively differentiate between 1 or 2 events. Petrologically, the rocks only preserve evidence for only one metamorphic event. However, this cannot be used as evidence to suggest one long hot event. If there were two events, the first may have reached the calculated UHT conditions, and the observed peak mineral assemblage crystallised then; or the second event reached
UHT conditions and overprinted the first. The data presented here is not sufficient to resolve this issue, and is something that needs to be addressed in the future. 49
The conservative interpretation taken from evidence presented here is that two events occurred within the Ongole Domain at ca. 1640 Ma and 1590 Ma. As discussed, the fundamental behavioural differences between monazite and zircon at granulite facies conditions could have attributed to the bimodal peak seen between the geochronometers; hence, the possibility of a long, hot orogen cannot be ruled out.
13.5 Tectonic implications for the Ongole Domain
The data presented here are used to hypothesise a schematic, geodynamic model for the
Paleoproterozoic evolution of the Ongole Domain; taking into account the previously published geochronological and geochemical data, and the geochronological and metamorphic constraints suggested by this work.
Recent studies provide increasing evidence for a major episode of passive rifting and intracontinental mafic magmatism along the SE margin of the Indian continent, between ca. 1890-1870 Ga (Chatterjee
& Bhattacharji 2001; French et al. 2008), leading to the formation of a wide ocean basin (Figure 29).
Isotopic and trace element detrital zircon data obtained in this study are the first of its kind in the
Ongole Domain; constraining the timing of sedimentary deposition to ca. 1850-1750 Ma.
The model suggests Paleoproterozoic sedimentation along the eastern margin of Antarctica, adjacent to the North Australian Craton (e.g Zhao et al. 2004); between ca. 1850-1750 Ma (Figure 29a).
Specifically, the Napier Complex is designated as the most appropriate area for deposition, as it shares a morphological fit with the southern EGB (Veevers 2009), and records deformation at ca. 1.55 Ga
(Owada et al. 2003). However, the model does not assume the evidence presented in this study equivocally supports deposition in this specific region. The present work highlights the need for 50 further geochronological and paleomagnetic data to be collected in the regions concerned, to support or refute the model.
Following rifting; thin, hot lithosphere along the SE coast of India gave way to generate oceanic crust at ca. 1.85 Ga (―Kandra Ophiolite Complex‖; Figure 29a; Kumar et al. 2010). On the basis of geochemical analysis, the oceanic crust is suggested to have formed in a suprasubduction-zone setting, typical of a continental back arc basin (Kumar et al., 2010; Dharma Rao et al., 2011b; Saha
2011). However, the driving mechanisms (i.e. slab pull vs. slab roll back and subduction polarity) behind the formation of oceanic crust is highly speculative (Dharma Rao et al., 2011b; Saha 2011).
Following results obtained during this study, a metamorphic event affecting the Ongole Domain sedimentary precursors is speculated at ca. 1750 Ma; but the nature of this event is entirely unconstrained (Figure 29b).
Oceanic decoupling initiated subduction, and the generation of an intra-oceanic island arc east of the
Indian subcontinent (Figure 29b) (Kumar et al., 2010). The culmination of subduction is interpreted to result from collisional orogenesis between the Napier Complex and the Dharwar Craton (Figure 29d;
Dobmeier et al., 2006; Simmat & Raith 2008; Mukhopadhyay & Basak 2009) at 1640 and 1590 Ma
(present study). Petrographic analysis suggests the P-T path associated with UHT metamorphism may not have been homogenous across the Ongole Domain. The rocks in Domain 1 are interpreted to preserve textural evidence for high temperature decompression, followed by isobaric cooling in the mid crust; whereas rocks in Domain 2 preserve only minor retrograde textures, which cannot be used to constrain a P-T path. However, the data obtained from these rocks are insufficient to resolve the apparent differences between the two domains.
Episodic magmatism accompanied metamorphism in both domains, spanning a minimum period of ca. 1640-1570 Ma (Figure 29c). Whole-rock geochemical analysis would allow for differentiation between pre, syn or late stage collisional magmatism (Harris et al. 1986); and should be employed for future research in the area. Following orogenesis, the Krishna Province underwent late 51
Mesoproterozoic rifting and alkaline magmatism, relating to the breakup of Nuna between 1600-1300
Ma (not shown in Figure 29; Simmat & Raith 2008). The youngest zircon and monazite grains analysed in this study (> ca. 1400 Ma) are tentatively attributed to this event.
14. CONCLUSIONS
The results presented in this study are a testament to the polyphase tectonism experienced by the
Ongole Domain during the Paleoproterozoic to Mesoproterozoic. U-Pb zircon geochronology constrains deposition of the sedimentary precursors to between ca. 1850-1750 Ma. The detrital components do not record a strong isotopic affinity with the Dharwar Craton, instead preserving geochemical similarities that can be traced to East Antarctica, North Australia and to a lesser extent, the North China Craton.
An unidentified metamorphic event is postulated to have occurred in the Ongole Domain at 1750 Ma, but cannot be substantiated by evidence found in this study. Monazite and zircon grains in metasedimentary and metaigneous rocks record evidence for metamorphic events at ca. 1640 Ma and
1590 Ma; which reached UHT conditions of 900-910°C and 9-9.2 kbar. Ti-in-zircon thermometry independently constrains the UHT conditions, generating temperature estimates of 935 ± 55°C for metamorphic overgrowths. Shortly following peak P-T conditions, the rock in Domain 1 are interpreted to have undergone isothermal decompression at high temperatures, followed by cooling at mid crustal levels. Trace element analysis of detrital zircon grains indicates partial to complete isotopic resetting and enhanced mobility of trace elements during UHT metamorphism. U-Pb dating and trace element analysis of zircons from meta-igneous rocks confirms syn-tectonic emplacement between ca. 1640-1570 Ma. Ti-in-zircon thermometry constrains the temperature of crystallisation to
~830-850°C. Coeval magmatism, and intermittent monazite and zircon growth over a ~50 myr period could indicate that metamorphism occurred as an ongoing event; and was possibly maintained by advective heat from the episodic intrusion of igneous bodies. Therefore, the possibility that the
Ongole Domain experienced hot, prolonged orogenesis cannot be ruled out and must be considered a 52 topic for future research. The results from this study provide support for continental reconstructions that link the southern Eastern Ghats Belt and East Antarctica during the late Paleoproterozoic.
15. ACKNOWLEDGEMENTS
I offer my sincere thanks to my supervisors Alan Collins and Caroline Forbes for all their help and guidance this year. Alan, thank you for giving me the opportunity to visit India; the experience was invaluable and enjoyable! Thank you both for having the patience to put up with me and my never ending stream of questions! Thank you to Guillaume for the enthusiastic, informative and often hilarious help in the field. Many, many thanks go to Justin Payne, Graham Baines and Martin Hand for helping me out with important bits and pieces throughout the course of my project. Gigantic thanks go to the legendary Dr. Katie Howard, master of the zircon, and all round great person.
I would also like to acknowledge that this project was funded by a joint Australian-Indian research grant, and would like to thank Dilip Saha, Parijat Nandi and Arnab Sain for the company and assistance in the field. Thank you to my India team, Emma, Andy, Ryan and Georgy for being great field companions. To the honours crew, I couldn‘t have picked a better bunch of people to spend the year with. I cannot thank you all enough for the support and some of the funniest moments I will ever experience. To those friends at uni who have known me the longest, especially Tanti, Sam, Ails, the
Shahins, Lou, Georgy, Gorey, Emma and Adam, I seriously couldn‘t have got through the degree without you. Seriously, without your smarts I would have failed many math-based practicals. To my outside-of-uni friends, especially Cheese, thank you for understanding my crazy obsession with rocks and being patient with me when I disappeared for months on end. To my family, and my Macky, thank you for the never ending support and love. To Ben thank you for being there and listening to me vent, and for giving me inspirational speeches when I needed them most.
16. REFERENCES
53
AGUE J. J. & BAXTER E. F. 2007. Brief thermal pulses during mountain building recorded by Sr diffusion in apatite and multicomponent diffusion in garnet. Earth and Planetary Science Letters 261, 500-516. ALEXANDER E. 2011. A geochronological and structural analysis of the Nallamalai Fold Belt, S.E. India. Earth and Environmental Sciences, University of Adelaide, Adelaide (unpubl.). ANAND M., GIBSON S. A., SUBBARAO K. V., KELLEY S. P. & DICKIN A. P. 2003. Early Proterozoic melt generation processes beneath the intra-cratonic Cuddapah Basin, southern India. Journal of Petrology 44, 2139-2171. ANDERSON T. 2005. Detrital zircons as tracers of sedimentary provenance: limiting conditions from statistics and numerical simulation. Chemical Geology 216, 249-270. APPEL P., MÖLLER* A. & SCHENK V. 1998. High-pressure granulite facies metamorphism in the Pan-African belt of eastern Tanzania: P–T–t evidence against granulite formation by continent collision. Journal of Metamorphic Geology 16, 491-509. ASAMI M., SUZUKI K. & GREW E. S. 2002. Chemical Th-U-total Pb dating by electron microprobe analysis of monazite, xenotime and zircon from the Archean Napier Complex, East Antarctica: evidence for ultra-high-temperature metamorphism at 2400 Ma. Precambrian Research 114, 249-275. ASAMI M., SUZUKI K., GREW E.S., AND ADACHI, M. 1998. CHIME ages for granulites from the Napier Complex, East Antarctica. Polar Geoscience 11, 172-199. ASHWAL L. D., TUCKER R. D. & ZINNER E. K. 1999. Slow cooling of deep crustal granulites and Pb-loss in zircon. Geochimica et Cosmochimica Acta 63, 2839-2851. AYERS J. C., DE LA CRUZ K., MILLER C. & SWITZER O. 2003. Experimental study of zircon coarsening in quartzite +/- H2O at 1.0 GPa and 1000 degrees C, with implications for geochronological studies of high-grade metamorphism. American Mineralogist 88, 365-376. BALLARD J., PALIN M. & CAMPBELL I. 2002. Relative oxidation states of magmas inferred from Ce(IV)/Ce(III) in zircon: application to porphyry copper deposits of northern Chile. Contributions to Mineralogy and Petrology 144, 347-364. BELOUSOVA E. A., REID A. J., GRIFFIN W. L. & O'REILLY S. Y. 2009. Rejuvenation vs. recycling of Archean crust in the Gawler Craton, South Australia: Evidence from U– Pb and Hf isotopes in detrital zircon. Lithos 113, 570-582. BELYATSKY B. V., RODIONOV N. V., SERGEEV S. A. & KAMENEV E. N. 2007. New evidence for the early Archean evolution of Aker Peaks, Napier Mountains, Enderby Land (East Antarctica). Extended Abstract 187, 1-4. BENTO DOS SANTOS T., MUNHÁ J., TASSINARI C., FONSECA P. & NETO C. 2011. Metamorphic P-T evolution of granulites in the central Ribeira Fold Belt, SE Brazil. Geosciences Journal 15, 27-51. BETTS P. G., GILES D. & SCHAEFER B. F. 2008. Comparing 1800–1600 Ma accretionary and basin processes in Australia and Laurentia: Possible geographic connections in Columbia. Precambrian Research 166, 81-92. BHANDARI A., CHANDRA PANT N., BHOWMIK S. K. & GOSWAMI S. 2011. ∼1.6 Ga ultrahigh- temperature granulite metamorphism in the Central Indian Tectonic Zone: insights from metamorphic reaction history, geothermobarometry and monazite chemical ages. Geological Journal 46, 198-216. BHASKAR RAO Y. J., PANTULU, G. V.C., REDDY, V.D. & GOPALAN, K (Editor) 1995. Time of early sedimentation and volcanism in the Proterozoic Cuddapah basin, South India: evidence from the Rb---Sr age of Pulivendla mafic sill. (Dyke Swarms of Penisular India, Vol. 33). Geological Society of India 54
BHATTACHARYA S. 1996. Eastern Ghats granulite terrain of India: An overview. Journal of Southeast Asian Earth Sciences 14, 165-174. BHATTACHARYA S. & CHAUDHARY A. K. 2010. Secular evolution of continental crust: recorded from massif-type charnockites of Eastern Ghats belt, India.(Report). Natural Science 2, 1079(1076). BHOWMIK S. K., WILDE S. A., BHANDARI A., PAL T. & PANT N. C. 2011. Growth of the Greater Indian Landmass and its Assembly in Rodinia: Geochronological evidence from the Central Indian Tectonic Zone. Gondwana Research. BHUI U. K., SENGUPTA P. & SENGUPTA P. 2007. Phase relations in mafic dykes and their host rocks from Kondapalle, Andhra Pradesh, India: Implications for the time-depth trajectory of the Palaeoproterozoic (late Archaean?) granulites from southern Eastern Ghats Belt. Precambrian Research 156, 153-174. BICKFORD M. E., MUELLER P. A., KAMENOV G. D. & HILL B. M. 2008. Crustal evolution of southern Laurentia during the Paleoproterozoic: Insights from zircon Hf isotopic studies of ca. 1.75 Ga rocks in central Colorado. Geology 36, 555-558. BIERLEIN F. P., BLACK L. P., HERGT J. & MARK G. 2008. Evolution of Pre-1.85 Ga basement rocks in the western Mt Isa Inlier, northeastern Australia—Insights from SHRIMP U– Pb dating and in-situ Lu–Hf analysis of zircons. Precambrian Research 163, 159-173. BOMPAROLA R. M., GHEZZO C., BELOUSOVA E., GRIFFIN W. L. & O'REILLY S. Y. 2007. Resetting of the U–Pb Zircon System in Cambro-Ordovician Intrusives of the Deep Freeze Range, Northern Victoria Land, Antarctica. Journal of Petrology 48, 327-364. BOSE S., DUNKLEY D. J., DASGUPTA S., DAS K. & ARIMA M. 2011. India-Antarctica- Australia-Laurentia connection in the Paleoproterozoic-Mesoproterozoic revisited: Evidence from new zircon U-Pb and monazite chemical age data from the Eastern Ghats Belt, India. Geological Society of America Bulletin 123, 2031-2049. BRANDT S., WILL T. M. & KLEMD R. 2007. Magmatic loading in the proterozoic Epupa Complex, NW Namibia, as evidenced by ultrahigh-temperature sapphirine-bearing orthopyroxene–sillimanite–quartz granulites. Precambrian Research 153, 143-178. CARSON C. J., AGUE J. J. & COATH C. D. 2002. U-Pb geochronology from Tonagh Island, East Antarctica: implications for the timing of ultra-high temperature metamorphism of the Napier Complex. Precambrian Research 116, 237-263. CHAMPION D. C. & SHERATON J. W. 1997. Geochemistry and Nd isotope systematics of Archaean granites of the eastern goldfields, Yilgarn Craton, Australia: Implications for crustal growth processes. Precambrian Research 83, 109-132. CHATTERJEE N. & BHATTACHARJI S. 2001. Petrology, geochemistry and tectonic settings of the mafic dikes and sills associated with the evolution of the Proterozoic Cuddapah Basin of South India. Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences 110, 433-453. CHAUDHURI A. K., SAHA D., DEB G. K., DEB S. P., MUKHERJEE M. K. & GHOSH G. 2002. The Purana basins of southern cratonic province of India - A case for mesoproterozoic fossil rifts. Gondwana Research 5, 23-33. CHEN R.-X., ZHENG Y.-F. & XIE L. 2010. Metamorphic growth and recrystallization of zircon: Distinction by simultaneous in-situ analyses of trace elements, U–Th–Pb and Lu–Hf isotopes in zircons from eclogite-facies rocks in the Sulu orogen. Lithos 114, 132-154. CHERNIAK D. J., WATSON E. B., GROVE M. & HARRISON T. M. 2004. Pb diffusion in monazite: a combined RBS/SIMS study. Geochimica et Cosmochimica Acta 68, 829- 840. CHOI S. H., MUKASA S. B., ANDRONIKOV A. V., OSANAI Y., HARLEY S. L. & KELLY N. M. 2006. Lu-Hf systematics of the ultra-high temperature Napier Metamorphic Complex 55
in Antarctica: Evidence for the early Archean differentiation of Earth's mantle. Earth and Planetary Science Letters 246, 305-316. CLAOUÉ-LONG J., MAIDMENT D., HUSSEY K. & HUSTON D. 2008. The duration of the Strangways Event in central Australia: Evidence for prolonged deep crust processes. Precambrian Research 166, 246-262. CLARK C., COLLINS A. S., SANTOSH M., TAYLOR R. & WADE B. P. 2009. The P-T-t architecture of a Gondwanan suture: REE, U–Pb and Ti-in-zircon thermometric constraints from the Palghat Cauvery shear system, South India. Precambrian Research 174, 129-144. CLARK C., FITZSIMONS I. C. W., HEALY D. & HARLEY S. L. 2011. How does the continental crust get really hot? Elements 7, 235-240. COLLINS A. S. & PISAREVSKY S. A. 2005. Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens. Earth-Science Reviews 71, 229-270. CONDIE K. C. & ASTER R. C. 2010. Episodic zircon age spectra of orogenic granitoids: The supercontinent connection and continental growth. Precambrian Research 180, 227- 236. CONDIE K. C., BELOUSOVA E., GRIFFIN W. L. & SIRCOMBE K. N. 2009. Granitoid events in space and time: Constraints from igneous and detrital zircon age spectra. Gondwana Research 15, 228-242. CORFU F., HANCHAR J. M., O. H. P. W. & 2003 K. P. D. (Editors) 2003. Atlas of zircon textures. (Zircon, Vol. Vol. 53). Mineralogical Society of America, Reviews in Mineralogy and Geochemistry, Washington, D.C. DALY S. J., FANNING C. M. & FAIRCLOUGH M. C. 1998. Tectonic evolution and exploration potential for the Gawler Craton, South Australia. AGSO Journal of Australian Geology and Geophysics 17, 145-168. DASGUPTA S., RAITH M. M. & SARKAR S. 2008. New perspectives in the study of the Precambrian continental crust of India: An integrated sedimentologic, isotopic, tectonometamorphic and seismological appraisal. Precambrian Research 162, 1-3. DEGELING H., EGGINS S. & ELLIS D. J. 2001. Zr budgets for metamorphic reactions, and the formation of zircon from garnet breakdown. Mineral Mag 65, 749-758. DHARMA RAO C. V., SANTOSH M. & DONG Y. 2011a. U–Pb zircon chronology of the Pangidi–Kondapalle layered intrusion, Eastern Ghats belt, India: Constraints on Mesoproterozoic arc magmatism in a convergent margin setting. Journal of Asian Earth Sciences. DHARMA RAO C. V., SANTOSH M. & WU Y.-B. 2011b. Mesoproterozoic ophiolitic mélange from the SE periphery of the Indian plate: U-Pb zircon ages and tectonic implications. Gondwana Research 19, 384-401. DHARMA RAO C. V., WINDLEY B. F. & CHOUDHARY A. K. 2011c. The Chimalpahad anorthosite Complex and associated basaltic amphibolites, Nellore Schist Belt, India: Magma chamber and roof of a Proterozoic island arc. Journal of Asian Earth Sciences 40, 1027-1043. DIENER J. F. A., WHITE R. W. & POWELL R. 2008. Granulite facies metamorphism and subsolidus fluid-absent reworking, Strangways Range, Arunta Block, central Australia. Journal of Metamorphic Geology 26, 603-622. DOBMEIER C., LUTKE S., HAMMERSCHMIDT K. & MEZGER K. 2006. Emplacement and deformation of the Vinukonda meta-granite (Eastern Ghats, India) - Implications for the geological evolution of peninsular India and for Rodinia reconstructions. Precambrian Research 146, 165-178. 56
DOBMEIER C., RAITH, M. (Editor) 2003. Crustal architecture and evolution of the Eastern Ghats Belt and adjacent regions of India. (Proterozoic East Gondwana: Supercontinent Assembly and Breakup, Vol. vol. 206.). Geol.Soc., London Spl. Publ. DRÜPPEL K., MCCREADY A. J. & STUMPFL E. F. 2009. High-K granites of the Rum Jungle Complex, N-Australia: Insights into the Late Archean crustal evolution of the North Australian Craton. Lithos 111, 203-219. ERNST R. E., WINGATE M. T. D., BUCHAN K. L. & LI Z. X. 2008. Global record of 1600– 700 Ma Large Igneous Provinces (LIPs): Implications for the reconstruction of the proposed Nuna (Columbia) and Rodinia supercontinents. Precambrian Research 160, 159-178. EVANS D. A. D. & MITCHELL R. N. 2011. Assembly and breakup of the core of Paleoproterozoic-Mesoproterozoic supercontinent Nuna. Geology 39, 443-446. FALSTER G. 2011. Geochronological and sedimentological constraints on the evolution of the lower Cuddapah Basin, India. Earth and Environmental sciences, University of Adelaide, Adelaide (unpubl.). FERRY J. M. & WATSON E. B. 2007. New thermodynamic models and revised calibrations for the Ti-in-zircon and Zr-in-rutile thermometers. Contributions to Mineralogy and Petrology 154, 429-437. FLOWERS R. M., SCHMITT A. K. & GROVE M. 2010. Decoupling of U-Pb dates from chemical and crystallographic domains in granulite facies zircon. Chemical Geology 270, 20- 30. FORBES C. J., GILES D., BETTS P. G., WEINBERG R. & KINNY P. D. 2007. Dating Prograde Amphibolite and Granulite Facies Metamorphism Using In Situ Monazite U-Pb SHRIMP Analysis. Journal of Geology 115, 691-705. FOSTER G., PARRISH R. R., HORSTWOOD M. S. A., CHENERY S., PYLE J. & GIBSON H. D. 2004. The generation of prograde P–T–t points and paths; a textural, compositional, and chronological study of metamorphic monazite. Earth and Planetary Science Letters 228, 125-142. FRASER G., ELLIS D. & EGGINS S. 1997. Zirconium abundance in granulite-facies minerals, with implications for zircon geochronology in high-grade rocks. Geology 25, 607- 610. FRENCH J. E. & HEAMAN L. M. 2010. Precise U–Pb dating of Paleoproterozoic mafic dyke swarms of the Dharwar craton, India: Implications for the existence of the Neoarchean supercraton Sclavia. Precambrian Research 183, 416-441. FRENCH J. E., HEAMAN L. M., CHACKO T. & SRIVASTAVA R. K. 2008. 1891-1883 Ma Southern Bastar-Cuddapah mafic igneous events, India: A newly recognized large igneous province. Precambrian Research 160, 308-322. FROST B. R., FROST C. D., HULSEBOSCH T. P. & SWAPP S. M. 2000. Origin of the Charnockites of the Louis Lake Batholith, Wind River Range, Wyoming. Journal of Petrology 41, 1759-1776. FU B., PAGE F. Z., CAVOSIE A. J., FOURNELLE J., KITA N. T., LACKEY J. S., WILDE S. A. & VALLEY J. W. 2008. Ti-in-zircon thermometry: applications and limitations. Contributions to Mineralogy and Petrology 156, 197-215. GEISLER T., SCHALTEGGER U. & TOMASCHEK F. 2007. Re-equilibration of zircon in aqueous fluids and melts. Elements 3, 43-50. GERDES A. & ZEH A. 2009. Zircon formation versus zircon alteration — New insights from combined U–Pb and Lu–Hf in-situ LA-ICP-MS analyses, and consequences for the interpretation of Archean zircon from the Central Zone of the Limpopo Belt. Chemical Geology 261, 230-243. 57
GILES D., BETTS P. G. & LISTER G. S. 2004. 1.8–1.5-Ga links between the North and South Australian Cratons and the Early–Middle Proterozoic configuration of Australia. Tectonophysics 380, 27-41. GORE R. 2011. Geochronological and sedimentological constraints of the Sirsailam Formation, S.E. India. Earth and Environmental Sciences, University of Adelaide, Adelaide (unpubl.). GREW E. S., MANTON W. I. & SANDIFORD M. 1982. Geochronologic studies in East Antarctica: age of pegmatites in Casey Bay, Enderby Land. Antarctic Journal of the United States 17, 1-2. GREW E. S., SUZUKI, K., AND ASAMI, M. 2001. CHIME ages of xenotime, monazite and zircon from beryllium pegmatites in the Napier Complex, Khmara Bay, Enderby Land, East Antarctica. Polar Geoscience 14, 99-118. GRIFFIN T. J., PAGE R. W., SHEPPARD S. & TYLER I. M. 2000. Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia. Precambrian Research 101, 1-23. GUPTA S. & BOSE S. 2004. Deformation history of the Kunavaram Complex, Eastern Ghats Belt, India: Implications for alkaline magmatism along the Indo-Antarctica suture. Gondwana Research 7, 1235-1241. HANCHAR J. M. & VAN WESTRENEN W. 2007. Rare earth element behavior in zircon-melt systems. Elements 3, 37-42. HAND M., REID A. & JAGODZINSKI L. 2007. Tectonic Framework and Evolution of the Gawler Craton, Southern Australia. Economic Geology 102, 1377-1395. HARLEY S. L. & BLACK L. P. 1997. A revised Archaean chronology for the Napier Complex, Enderby Land, from SHRIMP ion-microprobe studies. Antarctic Science 9, 74-91. HARRIS N. B. W., PEARCE J. A. & TINDLE A. G. 1986. Geochemical characteristics of collision-zone magmatism. Geological Society, London, Special Publications 19, 67- 81. HARRISON T. M. & SCHMITT A. K. 2007. High sensitivity mapping of Ti distributions in Hadean zircons. Earth and Planetary Science Letters 261, 9-19. HOEK J. D. & SEITZ H. M. 1995. Continental mafic dyke swarms as tectonic indicators: an example from the Vestfold Hills, East Antarctica. Precambrian Research 75, 121- 139. HOFMANN A. E., VALLEY J. W., WATSON E. B., CAVOSIE A. J. & EILER J. M. 2009. Sub- micron scale distributions of trace elements in zircon. Contributions to Mineralogy and Petrology 158, 317-335. HÖGDAHL K., MAJKA J., SJÖSTRÖM H., NILSSON K., CLAESSON S. & KONEČNÝ P. 2011. Reactive monazite and robust zircon growth in diatexites and leucogranites from a hot, slowly cooled orogen: implications for the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield, Sweden. Contributions to Mineralogy and Petrology, 1-22. HOLLAND T. J. B. & POWELL R. 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology 16, 309-343. HORIE K., HOKADA T., HIROI Y., MOTOYOSHI Y. & SHIRAISHI K. 2011. Contrasting Archaean crustal records in western part of the Napier Complex, East Antarctica: New constraints from SHRIMP geochronology. Gondwana Research. HOSKIN P. W. O. & BLACK L. P. 2000. Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon. Journal of Metamorphic Geology 18, 423-439. HOSKIN P. W. O. & IRELAND T. R. 2000. Rare earth element chemistry of zircon and its use as a provenance indicator. Geology 28, 627-630. 58
HOSKIN P. W. O. & SCHALTEGGER U. 2003. The composition of zircon and igneous and metamorphic petrogenesis. In: Hanchar J. M. & Hoskin P. W. O. eds., Zircon, Vol. 53, pp 27-62. HOU G., SANTOSH M., QIAN X., LISTER G. S. & LI J. 2008. Configuration of the Late Paleoproterozoic supercontinent Columbia: Insights from radiating mafic dyke swarms. Gondwana Research 14, 395-409. HOWARD K. E., HAND M., BAROVICH K. M., PAYNE J. L. & BELOUSOVA E. A. 2011. U–Pb, Lu–Hf and Sm–Nd isotopic constraints on provenance and depositional timing of metasedimentary rocks in the western Gawler Craton: Implications for Proterozoic reconstruction models. Precambrian Research 184, 43-62. HOWARD K. E., HAND M., BAROVICH K. M., REID A., WADE B. P. & BELOUSOVA E. A. 2009. Detrital zircon ages: Improving interpretation via Nd and Hf isotopic data. Chemical Geology 262, 277-292. HURAI V., PAQUETTE J. L., HURAIOVÁ M. & KONEČNÝ P. 2010. U–Th–Pb geochronology of zircon and monazite from syenite and pincinite xenoliths in Pliocene alkali basalts of the intra-Carpathian back-arc basin. Journal of Volcanology and Geothermal Research 198, 275-287. IIZUKA T., KOMIYA T., JOHNSON S. P., KON Y., MARUYAMA S. & HIRATA T. 2009. Reworking of Hadean crust in the Acasta gneisses, northwestern Canada: Evidence from in-situ Lu–Hf isotope analysis of zircon. Chemical Geology 259, 230-239. ISHIZUKA H. 2008. An overview of geological studies of JARE in the Napier Complex, Enderby Land, East Antarctica. Geological Society, London, Special Publications 308, 121-138. JAYANANDA M., MOYEN J. F., MARTIN H., PEUCAT J. J., AUVRAY B. & MAHABALESWAR B. 2000. Late Archaean (2550-2520 Ma) juvenile magmatism in the Eastern Dharwar craton, southern India: constraints from geochronology, Nd-Sr isotopes and whole rock geochemistry. Precambrian Research 99, 225-254. KATO M., MITSUI H., KOBAYASHI T., HIROI Y., SATISH-KUMAR M., DUNKLEY D. J. & HOKADA T. 2010. New finding of kyanite and andalusite in sillimanite-rich pelitic granulites from the Kerala Khondalite Belt, Southern India. Journal of Mineralogical and Petrological Sciences 105, 328-333. KELSEY D. 2008. On ultrahigh-temperature crustal metamorphism. Gondwana Research 13, 1-29. KELSEY D. E., CLARK C. & HAND M. 2008. Thermobarometric modelling of zircon and monazite growth in melt-bearing systems: examples using model metapelitic and metapsammitic granulites. Journal of Metamorphic Geology 26, 199-212. KORHONEN F. J., SAW A. K., CLARK C., BROWN M. & BHATTACHARYA S. 2011. New constraints on UHT metamorphism in the Eastern Ghats Province through the application of phase equilibria modelling and in situ geochronology. Gondwana Research 20, 764-781. KOVACH V. P., SIMMAT R., RICKERS K., BEREZHNAYA N. G., SALNIKOVA E. B., DOBMEIER C., RAITH M. M., YAKOVLEVA S. Z. & KOTOV A. B. 2001. The Western Charnockite Zone of the Eastern Ghats Belt, India -- An Independent Crustal Province of Late Archaean (2.8 Ga) and Palaeoproterozoic (1.7--1.6 Ga) Terrains. Gondwana Research 4, 666-667. KRYZA R., CROWLEY Q. G., LARIONOV A., PIN C., OBERC-DZIEDZIC T. & MOCHNACKA K. 2011. Chemical abrasion applied to SHRIMP zircon geochronology: An example from the Variscan Karkonosze Granite (Sudetes, SW Poland). Gondwana Research. KUMAR A. 2008. EVOLUTION OF THE EASTERN GHATS BELT, INDIA: A PLATE TECTONIC PERSPECTIVE. Journal of the Geological Society of India 72. 59
KUMAR K. V., ERNST W. G., LEELANANDAM C., WOODEN J. L. & GROVE M. J. 2010. First Paleoproterozoic ophiolite from Gondwana: Geochronologic-geochemical documentation of ancient oceanic crust from Kandra, SE India. Tectonophysics 487, 22-32. KUMAR K. V. & LEELANANDAM C. 2008. Evolution of the Eastern Ghats Belt, India: A Plate Tectonic Perspective. Journal of the Geological Society of India 72, 720-749. KUSKY T. M. & LI J. 2003. Paleoproterozoic tectonic evolution of the North China Craton. Journal of Asian Earth Sciences 22, 383-397. LANCASTER P. J., BAXTER E. F., AGUE J. J., BREEDING C. M. & OWENS T. L. 2008. Synchronous peak Barrovian metamorphism driven by syn-orogenic magmatism and fluid flow in southern Connecticut, USA. Journal of Metamorphic Geology 26, 527- 538. LANYON R., BLACK L. P. & SEITZ H.-M. 1993. U-Pb zircon dating of mafic dykes and its application to the Proterozoic geological history of the Vestfold Hills, East Antarctica. Contributions to Mineralogy and Petrology 115, 184-203. LI Z. X., BOGDANOVA S. V., COLLINS A. S., DAVIDSON A., DE WAELE B., ERNST R. E., FITZSIMONS I. C. W., FUCK R. A., GLADKOCHUB D. P., JACOBS J., KARLSTROM K. E., LU S., NATAPOV L. M., PEASE V., PISAREVSKY S. A., THRANE K. & VERNIKOVSKY V. 2008. Assembly, configuration, and break-up history of Rodinia: A synthesis. Precambrian Research 160, 179-210. LIU X. C., JAHN B. M., HU J., LI S. Z., LIU X. & SONG B. 2011. Metamorphic patterns and SHRIMP zircon ages of medium-to-high grade rocks from the Tongbai orogen, central China: implications for multiple accretion/collision processes prior to terminal continental collision. Journal of Metamorphic Geology 29, 979-1002. LUDWIG K. R. 2003. Isoplot/EX version 3.0. Berkely Geochronology Center Special Publication. Excel A. g. t. f. M. MAIDMENT D. W., HAND M. & WILLIAMS I. S. 2005. Tectonic cycles in the Strangways Metamorphic Complex, Arunta Inlier, central Australia: geochronological evidence for exhumation and basin formation between two high-grade metamorphic events*. Australian Journal of Earth Sciences 52, 205-215. MARTIN L. A. J., DUCHÊNE S., DELOULE E. & VANDERHAEGHE O. 2008. Mobility of trace elements and oxygen in zircon during metamorphism: Consequences for geochemical tracing. Earth and Planetary Science Letters 267, 161-174. MEERT J. G. 2003. A synopsis of events related to the assembly of the eastern Gondwana. Tectonophysics 362, 1-40. MELDRUM A., BOATNER L. A., WEBER W. J. & EWING R. C. 1998. Radiation damage in zircon and monazite. Geochimica et Cosmochimica Acta 62, 2509-2520. MELLETON J., FAURE M. & COCHERIE A. 2009. Monazite U-Th/Pb chemical dating of the Early Carboniferous syn-kinematic MP/MT metamorphism in the Variscan French Massif Central. Bulletin de la Societe Geologique de France 180, 283-292. MEZGER K. & COSCA M. A. 1999. The thermal history of the Eastern Ghats Belt (India) as revealed by U-Pb and 40Ar/39Ar dating of metamorphic and magmatic minerals: implications for the SWEAT correlation. Precambrian Research 94, 251-271. MILLER B. V., FETTER A. H. & STEWART K. G. 2006. Plutonism in three orogenic pulses, Eastern Blue Ridge Province, southern Appalachians. Geological Society of America Bulletin 118, 171-184. MOHANTY S. 2011. Palaeoproterozoic assembly of the Napier Complex, Southern India and Western Australia: Implications for the evolution of the Cuddapah basin. Gondwana Research 20, 344-361. 60
MONTEL, KORNPROBST & VIELZEUF 2000. Preservation of old U–Th–Pb ages in shielded monazite: example from the Beni Bousera Hercynian kinzigites (Morocco). Journal of Metamorphic Geology 18, 335-342. MUKHERJEE M. K. 2001. Structural pattern and kinematic framework of deformation in the southern Nallamalai fold-fault belt, Cuddapah district, Andhra Pradesh, Southern India. Journal of Asian Earth Sciences 19, 1-15. MUKHOPADHYAY D. & BASAK K. 2009. The Eastern Ghats Belt - A Polycyclic Granulite Terrain. Journal of the Geological Society of India 73, 489-518. MURTHY Y. G. K., RAO, V.B., GUPTASARMA, D., RAO, J.M., RAO, M.N. & BHATTACHARJI, S 1987. Tectonic, petrochemical and geophysical studies of mafic dyke swarms around the Proterozoic Cuddapah basin, South India. Geological Association of Canada 34, 303-316. NAQVI S. M. 2005. Geology and evolution of the Indian plate : from Hadean to the Holocene, 4 Ga to 4 Ka Capital Pub. Co, New Delhi NEMCHIN A. A., GRANGE M. L. & PIDGEON R. T. 2010. Distribution of rare earth elements in lunar zircon. American Mineralogist 95, 273-283. NUTMAN A. P., BENNETT V. C., KINNY P. D. & PRICE R. 1993. LARGE-SCALE CRUSTAL STRUCTURE OF THE NORTHWESTERN YILGARN-CRATON, WESTERN- AUSTRALIA - EVIDENCE FROM ND ISOTOPIC DATA AND ZIRCON GEOCHRONOLOGY. Tectonics 12, 971-981. OWADA M., OSANAI Y., TOYOSHIMA T., TSUNOGAE T., HOKADA T., CROWE W. A. & KAGAMI H. 2003. Early Proterozoic Tectonothermal Events in the Napier Complex, East Antarctica: Implications for the Formation of East Gondwana. Gondwana Research 6, 231-240. PANDEY B. K., CHABRIA T. & GUPTA J. N. 1995. Geochronological characterisation of the Proterozoic terrains of Peninsular India: relevance to the first order target selection for uranium exploration. Exploration & Research for Atomic Minerals 8, 187-213. PANDEY B. K., GUPTA J. N., SARMA K. J. & SASTRY C. A. 1997. Sm-Nd, Pb-Pb and Rb-Sr geochronology and petrogenesis of the mafic dyke swarm of Mahbubnagar, South India: Implications for Paleoproterozoic crustal evolution of the Eastern Dharwar Craton. Precambrian Research 84, 181-196. PAYNE J. L., BAROVICH K. A. & HAND M. 2006a. Provenance of metasedimentary rocks in the northern Gawler Craton, Australia: Implications for palaeoproterozoic reconstructions. Precambrian Research 148, 275-291. PAYNE J. L., BAROVICH K. M. & HAND M. 2006b. Provenance of metasedimentary rocks in the northern Gawler Craton, Australia: Implications for Palaeoproterozoic reconstructions. Precambrian Research 148, 275-291. PAYNE J. L., HAND M., BAROVICH K. M. & WADE B. P. 2008. Temporal constraints on the timing of high-grade metamorphism in the northern Gawler Craton: implications for assembly of the Australian Proterozoic. Australian Journal of Earth Sciences 55, 623- 640. PECK W. H., BICKFORD M. E., MCLELLAND J. M., NAGLE A. N. & SWARR G. J. 2010. Mechanism of metamorphic zircon growth in a granulite-facies quartzite, Adirondack Highlands, Grenville Province, New York. American Mineralogist 95, 1796-1806. PIDGEON R. T., NEMCHIN A. A. & HITCHEN G. J. 1998. Internal structures of zircons from Archaean granites from the Darling Range batholith: implications for zircon stability and the interpretation of zircon U-Pb ages. Contributions to Mineralogy and Petrology 132, 288-299. PIETER V. 2004. How many grains are needed for a provenance study? Earth and Planetary Science Letters 224, 441-451. 61
POWELL C. M., LI Z. X., MCELHINNY M. W., MEERT J. G. & PARK J. K. 1993. Paleomagnetic constraints on timing of the Neoproterozoic breakup of Rodinia and the Cambrian formation of Gondwana. Geology 21, 889-892. POWELL R. & HOLLAND T. 2010. Using Equilibrium Thermodynamics to Understand Metamorphism and Metamorphic Rocks. Elements 6, 309-314. POWELL R. & HOLLAND T. J. B. 1988. AN INTERNALLY CONSISTENT DATASET WITH UNCERTAINTIES AND CORRELATIONS .3. APPLICATIONS TO GEOBAROMETRY, WORKED EXAMPLES AND A COMPUTER-PROGRAM. Journal of Metamorphic Geology 6, 173-204. RAMAKRISHNAN M., NANDA, J.K. & AUGUSTINE, P.F 1998. Geologic evolution of the Proterozoic Eastern Ghats Mobile Belt. Geological Survey of India Special Publication 44, 1-21. RAMAKRISHNAN M., VAIDYANADHAN, R. 2010. Geology of India Geological Society of India, Bangalore. RAVIKANT V. 2010. Palaeoproterozoic (~1.9 Ga) extension and breakup along the eastern margin of the Eastern Dharwar Craton, SE India: New Sm-Nd isochron age constraints from anorogenic mafic magmatism in the Neoarchean Nellore greenstone belt. Journal of Asian Earth Sciences 37, 67-81. RICKERS K., MEZGER K. & RAITH M. M. 2001. Evolution of the Continental Crust in the Proterozoic Eastern Ghats Belt, India and new constraints for Rodinia reconstruction: implications from Sm-Nd, Rb-Sr and Pb-Pb isotopes. Precambrian Research 112, 183-210. ROBERTS M. P. & FINGER F. 1997. Do U-Pb zircon ages from granulites reflect peak metamorphic conditions? Geology 25, 319-322. ROGERS J. J. W. & SANTOSH M. 2002. Configuration of Columbia, a mesoproterozoic supercontinent. Gondwana Research 5, 5-22. RUBATTO D. 2002. Zircon trace element geochemistry: partitioning with garnet and the link between U-Pb ages and metamorphism. Chemical Geology 184, 123-138. RUBATTO D., WILLIAMS I. S. & BUICK I. S. 2001. Zircon and monazite response to prograde metamorphism in the Reynolds Range, central Australia. Contributions to Mineralogy and Petrology 140, 458-468. SAHA D. 2002. Multi-stage deformation in the Nallamalai Fold Belt, Cuddapah basin, South India - Implications for Mesoproterozoic tectonism along southeastern margin of India. Gondwana Research 5, 701-719. SAHA D. 2011. Dismembered ophiolites in Paleoproterozoic nappe complexes of Kandra and Gurramkonda, South India. Journal of Asian Earth Sciences 42, 158-175. SANTOSH M. & KUSKY T. M. 2009. Ridge subduction model for HP-UHT orogens. Terra Nova 22, 35-42. SCHALTEGGER U., FANNING C. M., GÜNTHER D., MAURIN J. C., SCHULMANN K. & GEBAUER D. 1999. Growth, annealing and recrystallization of zircon and preservation of monazite in high-grade metamorphism: conventional and in-situ U-Pb isotope, cathodoluminescence and microchemical evidence. Contributions to Mineralogy and Petrology 134, 186-201. SENGUPTA P., DASGUPTA S., BHUI U. K., EHL J. & FUKUOKA M. 1996. Magmatic evolution of mafic granulites from Anakapalle, Eastern Ghats, India: Implications for tectonic setting of a Precambrian high-grade terrain. Journal of Southeast Asian Earth Sciences 14, 185-198. SENGUPTA P., SEN J., DASGUPTA S., RAITH M., BHUI U. K. & EHL J. 1999. Ultra-high temperature metamorphism of metapelitic granulites from Kondapalle, Eastern Ghats 62
Belt: Implications for the Indo-Antarctic correlation. Journal of Petrology 40, 1065- 1087. SIMMAT R. & RAITH M. M. 2008. U-Th-Pb monazite geochronometry of the Eastern Ghats Belt, India: Timing and spatial disposition of poly-metamorphism. Precambrian Research 162, 16-39. TARTÈSE R., RUFFET G., POUJOL M., BOULVAIS P. & IRELAND T. R. 2011. Simultaneous resetting of the muscovite K-Ar and monazite U-Pb geochronometers: a story of fluids. Terra Nova, no-no. TAYLOR R. & MCLENNAN S. M. 1985. The continental crust: Its composition and evolution. Blackwell Scientific Pub, Palo Alto, CA. TEALE W., COLLINS A. S., FODEN J., PAYNE J. L., PLAVSA D., CHETTY T. R. K., SANTOSH M. & FANNING M. 2011. Cryogenian (∼830 Ma) mafic magmatism and metamorphism in the northern Madurai Block, southern India: A magmatic link between Sri Lanka and Madagascar? Journal of Asian Earth Sciences 42, 223-233. TICHOMIROWA M., WHITEHOUSE M. J. & NASDALA L. 2005. Resorption, growth, solid state recrystallisation, and annealing of granulite facies zircon—a case study from the Central Erzgebirge, Bohemian Massif. Lithos 82, 25-50. UPADHYAY. D. G. A., RAITH. M.M. 2009. Unraveling Sedimentary Provenance and Tectonothermal History of High-Temperature Metapelites, Using Zircon and Monazite Chemistry: A Case Study from the Eastern Ghats Belt, India. 117, 665-683. VASUDEN D. 2003. Geochemistry, Petrogenesis and age of felsic to intermediate metavolcanic rocks from the Palaeoproterozoic Nellore schist belt, Vinjamur, Andhra Pradesh, India. Journal of Asian Earth Sciences 1367. VAVRA G. & SCHALTEGGER U. 1999. Post-granulite facies monazite growth and rejuvenation during Permian to Lower Jurassic thermal and fluid events in the Ivrea Zone (Southern Alps). Contributions to Mineralogy and Petrology 134, 405-414. VEEVERS J. 2009. Palinspastic (pre-rift and -drift) fit of India and conjugate Antarctica and geological connections across the suture. Gondwana Research 16, 90-108. VERVOORT J. D., PATCHETT P. J., BLICHERT-TOFT J. & ALBARÈDE F. 1999. Relationships between Lu-Hf and Sm-Nd isotopic systems in the global sedimentary system. Earth and Planetary Science Letters 168, 79-99. VIJAYA KUMAR K., ERNST W. G., LEELANANDAM C., WOODEN J. L. & GROVE M. J. 2010. First Paleoproterozoic ophiolite from Gondwana: Geochronologic-geochemical documentation of ancient oceanic crust from Kandra, SE India. Tectonophysics 487, 22-32. VIJAYA KUMAR K., LEELANANDAM C. & ERNST W. G. 2011. Formation and fragmentation of the Palaeoproterozoic supercontinent Columbia: evidence from the Eastern Ghats Granulite Belt, southeast India. International Geology Review 53, 1297-1311. WAN Y., LIU D., DONG C., LIU S., WANG S. & YANG E. 2011. U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta- diorite near Qixia, eastern Shandong. Geoscience Frontiers 2, 137-146. WANG H., WU Y.-B., GAO S., ZHANG H.-F., LIU X.-C., GONG H.-J., PENG M., WANG J. & YUAN H.-L. 2011. Silurian granulite-facies metamorphism, and coeval magmatism and crustal growth in the Tongbai orogen, central China. Lithos 125, 249-271. WATSON E. B. & HARRISON T. M. 2005. Zircon Thermometer Reveals Minimum Melting Conditions on Earliest Earth. Science 308, 841-844. WEISS S. & TROLL G. 1989. The ballachulish igneous complex, scotland: Petrography, mineral chemistry, and order of crystallization in the monzodiorite-quartz diorite suite and in the granite. Journal of Petrology 30, 1069-1115. 63
WHITEHOUSE M. J. 2000. Combining in Situ zircon REE and U-Th-Pb geochronology: A petrogenetic dating tool. Goldschmidt 2000, Oxford, UK (unpubl.). WHITMEYER S. J. & KARLSTROM K. E. 2007. Tectonic model for the Proterozoic growth of North America. Geosphere 3, 220-259. WILLIAMS M. L., JERCINOVIC M. J., HARLOV D. E., BUDZYŃ B. & HETHERINGTON C. J. 2011. Resetting monazite ages during fluid-related alteration. Chemical Geology 283, 218- 225. WINTER J. D. 2010. Principles of Igenous and Metamorphic Petrology (Vol. 2). Pearson Education, New Jersey. WU Y. 2004. Genesis of zircon and its constraints on interpretation of U-Pb age Chinese Science Bulletin 49 1554 - 1569 WU Y. & ZHENG Y. 2004. Genesis of zircon and its constraints on interpretation of U-Pb age. Chinese Science Bulletin 49, 1554-1569. XIANG W., GRIFFIN W. L., JIE C., PINYUN H. & XIANG L. I. 2011. U and Th Contents and Th/U Ratios of Zircon in Felsic and Mafic Magmatic Rocks: Improved Zircon-Melt Distribution Coefficients. Acta Geologica Sinica - English Edition 85, 164-174. YIN C., ZHAO G., GUO J., SUN M., XIA X., ZHOU X. & LIU C. 2011. U–Pb and Hf isotopic study of zircons of the Helanshan Complex: Constrains on the evolution of the Khondalite Belt in the Western Block of the North China Craton. Lithos 122, 25-38. YUAN H.-L., GAO S., DAI M.-N., ZONG C.-L., GÜNTHER D., FONTAINE G. H., LIU X.-M. & DIWU C. 2008. Simultaneous determinations of U–Pb age, Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple- collector ICP-MS. Chemical Geology 247, 100-118. ZACHARIAH J. K., HANSON G. N. & RAJAMANI V. 1995. Postcrystallization disturbance in the neodymium and lead isotope systems of metabasalts from the Ramagiri schist belt, southern India. Geochimica et Cosmochimica Acta 59, 3189-3203. ZHAO G. C., CAWOOD P. A., WILDE S. A. & SUN M. 2002. Review of global 2.1-1.8 Ga orogens: implications for a pre-Rodinia supercontinent. Earth-Science Reviews 59, 125-162. ZHAO G. C., SUN M., WILDE S. A. & LI S. Z. 2004. A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup. Earth-Science Reviews 67, 91-123. ZHAO J. X. & MCCULLOCH M. T. 1995. Geochemical and Nd isotopic systematics of granites from the Arunta Inlier, central Australia: implications for Proterozoic crustal evolution. Precambrian Research 71, 265-299. ZHENG Y. F., GAO T. S., WU Y. B., GONG B. & LIU X. M. 2007. Fluid flow during exhumation of deeply subducted continental crust: zircon U-Pb age and O-isotope studies of a quartz vein within ultrahigh-pressure eclogite. Journal of Metamorphic Geology 25, 267-283.
17. Figure and Table captions
Table 1) Detailed description of the lithologies, structure and contact relationships in Domain 1 (Appendix II)
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Table 2) Detailed description of the lithologies, structure and contact relationships in Domain 2. (Appendix II)
Table 3) Detailed description of the lithologies, structure and contact relationships in Domain 2. (Appendix II)
Table 4) Detailed description of the lithologies, structure and contact relationships in Domain 2. (Appendix II)
Table 5) Whole rock geochemistry for sample BH08, BH09, BH16, I0508. Diener et al. (2008) is the whole rock geochemistry for the sample used for comparison to sample BH08.
Table 6) Representative EPMA analyses of samples BH08, BH09 and BH16.
Table 7) Zircon geochronology tables for samples BH08, BH12, BH15, BH16, BH17, BH19, BH22. Samples in red denote that analysis was discarded.
Table 8a) Zircon CL descriptions for metaigneous samples (BH12, BH15, BH17, BH19, BH22)
Table 8b) Zircon CL descriptions for metasedimentary samples (BH08, BH16, I0508)
Table 9) BSE descriptions of monazite grains and textural descriptions.
Table 10) Monazite geochronology tables for samples BH08, BH09, BH16. Samples in red denote that the analysis was discarded.
Table 11) Zircon chondrite normalised REE values for samples BH08, BH16, I0508, BH15, BH17.
Table 12) Table summarising all Lu-Hf data obtained for samples BH08, BH16, I0508.
Table 13) Summary of published U-Pb zircon geochronology and Lu-Hf data for East Antarctica, the Dharwar Craton, North Australian Craton and the North China Craton.
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Figure 1. a) Simplified geological map of India showing the location of the southern Eastern Ghats Belt and Krishna Province. Includes the following abbreviations: CB:Cuddapah Basin; SGT: Southern Granulite Terrane; EGB: Eastern Ghats Belt; WDC: West Dhawar Craton; EDC; Eastern Dhawar Craton; SC: Singhbhum Craton; AC: Aravalli Craton; BC: Bastar Craton (Modified after French et al. (2008)).
Figure. 1b) The Eastern Ghats Belt showing subdivision into tectonic provinces, including the Mesozoic rift basins; the Mahanadi Rift in the north and the Godavari Rift in the South. Image is modified from Mukhopadhyay and Basak (2009).
Figure. 1c) Simplified geological map showing the location of the southern Eastern Ghats Belt.; Highlights the subdivision of the Krishna Province into individual domains. Sample locations from this study are shown in the boxes (1 & 2). Sample numbers are displayed in the legend and detailed lithological and geochronological descriptions are given in Table 1. Image modified from Dobmeier et al. (2006).
Figure. 2a) Simplified lithological map of Domain 1 showing location of outcropping rocks, and dominant structures. Lithological boundaries are interpreted from satellite imagery. Sample locations are shown with yellow star.
Figure. 2b) Simplified lithological map of Domain 2 showing location of outcropping rocks, dominant structures, and contact relationships. Lithological boundaries are interpreted from satellite imagery. Sample locations are shown with yellow star.
Figure. 3) Field photographs a) Isoclinal folding within garnet-sillimanite metapelite, b) aphanitic metabasite showing isoclinals folding and shearing of limbs, c) foliated pyroxenite d) fine grained sillimanite and quartz wrapping around porphyroblasts of garnet in garnet-sillimanite metapelite, e) large (~10cm) garnet porphyroblasts in the garnet-sillimanite metapelite, f) garnet bearing granitic intrusion in garnet-sillimanite metapelite, g) undeformed quartz-k-feldspar granite intruding garnet- sillimanite metapelite, h) garnet-sillimanite metapelite showing cross cutting relationships with garnet bearing granite (pink) and quartz-k-feldspar granite (white) intruding garnet bearing granite. All lithologies are cross cut by north south trending quartz veins (yellow). Figure. 4) Field photographs a) pyroxene bearing metagranite (charnockite) with diffuse pegmatites, b) allanite within pegmatite, c) strong gneissic fabric within charnockite which bends through the 66
pegmatite, d) charnockite with interpreted insitu diatexite, mafic dyke and folded mafic xenoliths, e) annotation showing the relationship between charnockite, diatexite, mafic dykes and mafic xenoliths, f) ultra mylonite zone showing sense of movement (top to the north), g) mafic dyke with chilled margins intruding charnockites.
Figure. 5) Field photographs a) weakly deformed charnockites with enclosing amphibolite, and intruding garnet bearing pegmatite at the contact zone between the two lithologies, b) massive charnockite body with ~1 m wide fine grained mafic dyke, c) annotated shear zone in charnockite showing deflection of fabric and grain size reduction in opx and quartz, d) boudinage in pegmatite, e) multiple pegmatite intrusion from left: micro granite with sharp contact to enclosing charnockites; coarse grained pegmatite; foliated and boudinaged pegmatite, f) diffuse veins within metagranite, g) mafic xenoliths hosted in granodiorite h) anastomosing networks of leucosomes in granodiorite, i) megacrystic granite with coarse grained pegmatite
Figure 6. Mineral abbreviations used: qz= quartz, ksp= k-feldspar, pl= plagioclase, bi= biotite, gt=garnet, mz=monazite, zi=zircon, opx= orthopyroxene, cpx=clinopyroxene, aperth=antiperthite, per=perthite, mag=magnetite, ilm=ilmenite. a) Photomicrograph of sample BH12 showing augen shaped k-feldspar porphyroblasts with biotite, magnetite wrapping around the grains. Fine grained quartz and k-feldspar rim the k-feldspar porphyroblasts, b) cross polarised photomicrograph of sample BH12 showing a fine grained mosaic of quartz, plagioclase and k-feldspar in a pressure shadow at the termination of a k-feldspar grain, c) photomicrograph of sample BH17 that shows the compositional layering of k-feldspar, quartz and plagioclase against orthopyroxene, clinopyroxene and magnetite, d) photomicrograph of clinopyroxene and orthopyroxene in sample BH15. Clinopyroxene displays simple and basal twinning, e) cross polar photomicrograph of large porphyroblasts of k-feldspar with inclusion of antiperthite in sample BH15. Myrmekitic texture is preserved in top centre of k-feldspar grain, f) sample BH10 cross polar photomicrograph of blebby dissolution texture in antiperthite, g) photomicrograph of sample BH10 showing anhedral garnet grains with inclusions of monazite and zircon, h) photomicrograph of sample BH10 showing clusters of cordierite, sillimanite, orthoamphibole and biotite throughout the rock, i) photomicrograph of BH19 showing lenticular quartz grains surrounded by plagioclase and perthite, j) photomicrograph of sample BH22 showing granoblastic texture and high abundance of perthite. Dark minerals are hornblende, biotite and an oxide, k) photomicrograph of hornblende surrounded by biotite, quartz and perthite, l) 67
photomicrograph of sample I0508 that demonstrates the weak alignment of sillimanite needles throughout the granoblastic matrix of perthite and quartz.
Figure. 7 a) photomicrograph of sample BH08 showing poikiloblastic G1 garnet with inclusions of monazite, quartz, sillimanite, b) photomicrograph of sample BH08 that shows the development of G2, with characteristic symplectic ilmenite growths. Note the relationship with sillimanite + orthoamphibole which marks the presence of relic cordierite, c) photomicrograph of sample BH08 that shows G1 garnet completely embayed by cordierite. Orthoamphibole + sillimanite forms an incomplete rim around cordierite, d) photomicrograph of sample BH08 showing cordierite grain with inclusions of apatite, rimmed by orthoamphibole + sillimanite, e) Photomicrograph of sample BH16 showing equant clusters of garnet with anhedral orthopyroxene grains in a matrix of quartz, k- feldspar and plagioclase, f) Photomicrograph of sample BH16 equant garnet grains with ilmenite and biotite forming incomplete rims around rims. Anhedral orthopyroxene grains are in direct contact with garnet, g) Photomicrograph of sample BH16 showing the contact between garnet and orthopyroxene. Garnet has inclusions of ilmenite.
Figure. 8) An overall photomicrograph showing the interpreted textural evolution of sample BH08. 1) peak mineral assemblage of garnet + sillimanite + ilmenite + quartz 2) a cordierite grain almost completely pseudomorphs relic G1 grains during replacement 3) the dominant secondary mineral assemblage of G2 garnet (sometimes with ilmenite symplectite intergrowths) and sillimanite- orthoamphibole replaces the cordierite. Forms dense fine grained mats often with coarse grains of ilmenite. 4) G2 garnet forming a rim around G1 garnet within cordierite. Note the sillimanite- orthoamphibole reaction forming at the edge of the cordierite grain.
Figure. 9) Calculated P-T pseudosection for sample BH16 with interpreted peak assemblage indicated by bold outline (garnet + opx + k-feldspar + quartz + liquid + ilmenite + plagioclase). Yopx isopleths are shown in pink, and x(g) isopleths are shown in red constraining the P-T conditions to ~9.2 kbar and 910°C. The (y(opx)The peak assemblage is represented by a red star.
Figure. 10) Sample BH12 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH12, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) 207Pb/206Pb weighted average of 100 ± 10% concordant data.
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Figure. 11) Sample BH15 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH15, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) 207Pb/206Pb weighted average of 100 ± 10% concordant data.
Figure. 12) Sample BH17 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH17, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) 207Pb/206Pb weighted average of 100 ± 10% concordant data.
Figure. 13) Sample BH19 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH19, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) 207Pb/206Pb weighted average of 100 ± 10% concordant data.
Figure. 14) Sample BH22 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH22, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) 207Pb/206Pb weighted average of 100 ± 10% concordant data.
Figure. 15) Sample BH08 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH08, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data , c) Unmix plot showing the two dominant populations found in sample BH08, d) Age display data showing the distribution of concordant data and discordant data.
Figure. 16) Sample BH16 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample BH16, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) Concordia plot of 100 ± 10% concordant data from the ca. 1860 – 1750 Ma peak, d) Age display data showing the distribution of concordant data and discordant data.
Figure. 17) Sample I0508 LA-ICP-MS U-Pb zircon geochronology data, a) representative CL images of zircon grains from sample I0508, b) Concordia plot of 100 ± 10% concordant data: inset top: concordia plot of all data, c) Age display data showing the distribution of concordant data and discordant data.
Figure. 18) Sample BH08, BH09 and BH16 insitu LA-ICP-MS U-Pb monazite geochronology data, a) Left: Concordia plot of 100 ± 10% concordant data for sample BH08 displayed in accordance to the textural location of monazite. Right: representative BSE image of textural relationships between 69
monazite grain and surrounding minerals; and representative BSE images of monazite grains analysed. b) Left: Concordia plot of 100 ± 10% concordant data for sample BH09 displayed in accordance to the textural location of monazite. Right: representative BSE image of textural relationships between monazite grain and surrounding minerals; and representative BSE images of monazite grains analysed. c) Left: Concordia plot of 100 ± 10% concordant data for sample BH16 displayed in accordance to the textural location of monazite. Right: representative BSE image of textural relationships between monazite grain and surrounding minerals; and representative BSE images of monazite grains analysed.
Figure. 19) Sample BH10 LA-ICP-MS U-Pb monazite geochronology data. Left: Concordia plot of 100 ± 10% concordant data for sample BH10. Right: representative BSE image of monazite grains.
Figure. 20) Rare Earth Element patterns for sample BH12 (a), BH15 (b), BH08 (c), BH16 (d) and I0508 (e).
Figure. 21) Ti-in-zircon thermometry results for samples BH15, BH17, BH08, BH16 and I0508. Error bars represent the error on the temperature estimates. Metasedimentary zircons are shown in accordance to the 207Pb/206Pb age. BH15 and BH17 are displayed in accordance to the CL location ablated.
Figure. 22) Hf isotope data from samples BH08, BH16 and I0508. a) ƐHf values plotted against U-Pb crystallisation ages for individual zircon grains. b) Initial 177Hf/176Hf values plotted against model ages for individual zircon grains. Grey analyses are excluded.
Figure. 23) Th/U ratios for samples BH12 (a), BH15 (b), BH08 (c) and BH16 (d). Individual zircon analyses are shown in accordance with the CL domain analysed.
Figure. 24) Time-Space plot constructed for potential source terranes considered for detrital zircon grains in the Ongole Domain. Detrital peaks obtained in this study are displayed as a yellow star. The data is compiled from (Grew et al. 1982; Lanyon et al., 1993; Nutman et al., 1993; Hoek & Seitz 1995; Champion & Sheraton 1997; Harley & Black 1997; Asami 1998; Daly et al. 1998; Griffin et al. 2000; Jayananda et al. 2000; Grew 2001; Asami et al. 2002; Carson et al. 2002; Anand et al., 2003; Kusky & Li 2003; Giles et al., 2004; Collins & Pisarevsky 2005; Maidment et al. 2005; Choi et al. 2006; Payne et al., 2006a; Belyatsky et al. 2007; Hand et al. 2007; Betts et al. 2008; Bickford et al., 2008; Bierlein et 70
al. 2008; Claoué-Long et al., 2008; Diener et al., 2008; French et al., 2008; Ishizuka 2008; Yuan et al., 2008; Belousova et al., 2009; Drüppel et al., 2009; French & Heaman 2010; Horie et al. 2011; Liu et al. 2011; Wang et al. 2011; Xiang et al. 2011; Yin et al. 2011)
Figure. 25) Comparative plot of all detrital zircon grains extracted from the Ongole Domain metasedimentary rocks, with those extracted from the lower Cuddapah Supergroup. The pink band highlights the prominent 2500 Ma peak. Data taken from Alexander (2011), Falster (2011) and Gore (2011).
Figure. 26) Modified after Zhao et al. (2004). A simplified reconstruction of Nuna (Columbia) at 1.85 Ga that highlights the possible source terrains for the metasedimentary rocks.
Figure. 27) Graph showing the overlapping igneous intrusions in the Ongole Domain, India.
Figure 28) Representative P-T pseudosection for simplified comparison to the P-T path undertaken by sample BH08/09. Taken from Diener et al. (2008). The interpreted metamorphic path taken is highlighted by the pink arrow. The numbers represent the interpreted phases in the mineral assemblage.
Figure. 29) Schematic geodynamic model proposed for the Paleoproterozoic evolution of the Ongole Domain. Modified from Kumar et al. (2010), the model shows the newly constrained timing of deposition for the Ongole Domain sediments. The Kandra Ophiolite and Kondapalle magmatic arc are documented by Kumar et al. (2010) and Bhui et al. (2007). Metamorphism is constrained by the geochronological data found in this study.
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20. Tables
SiO2 TiO Al2O FeO Mn Mg CaO Na2 K2O P2O TOTAL 2 3 O O O 5 BH08 49.6 1.24 19.79 19.8 0.25 8.26 0.7 0.10 0.0 0.04 100.0 6 8 3 4 0 BH09 53.2 1.29 17.60 18.7 0.12 7.95 0.7 0.02 0.1 0.04 100.0 9 9 5 4 0 BH16 74.1 0.42 9.50 5.12 0.06 2.39 3.3 2.45 2.5 0.02 100.0 1 4 7 0 BHI05-08 86.2 0.15 8.85 0.39 0.00 0.05 0.1 1.76 2.4 0.00 100.0 2 4 5 0 Diener et al. 67.7 1.23 16.33 9.18 0.05 5.29 0.1 0.23 0.2 0.01 100.4 (2008) 5 5 2 Table 5
1
BH08/09 BH16 Mineral Garnet Spinel Plagioclase Cordierite Ilmenite Biotite Magnetite Opx Garnet Pl Ksp Bi Ilm
SiO2 38.0087 0.0267 56.021 48.1176 0.111 36.7335 0.0301 48.0286 38.9958 56.913 62.9411 36.7335 0.0573 TiO2 0.0321 0.0072 0.0165 0.0136 24.851 4.5445 0.0002 0.1473 0.0291 0.0293 0.0002 4.5445 52.0257 Al2O3 21.6016 58.2173 25.0381 32.1824 0.081 13.3756 0.149 4.1087 22.5551 25.5857 18.3339 13.3756 0.0003 Cr2O3 0.0318 0.2352 0.0002 0.0175 0.082 0.0333 0.1316 0.028 0.0213 0.0259 0.0386 0.0333 0.0002 FeO 25.2729 17.9296 0.0002 2.9565 68.606 13.5784 88.9768 29.284 31.3297 0.0792 0.0234 13.5784 42.4871 MnO 0.6225 0.0002 0.0118 0.0002 0.089 0.0928 0.0001 0.2558 0.7681 0.0002 0.0002 0.0928 0.1748 MgO 10.625 9.7177 0.0026 11.7955 0.590 14.9539 0.0031 15.9912 7.3845 0.0003 0.0002 14.9539 1.0239 ZnO 0.029 10.4084 0.0834 0.0002 0.007 0.1118 0.0273 0.0058 0.0002 0.0002 0.0002 0.1118 0.0511 CaO 1.3998 0.0002 8.0888 0.0002 0.071 0.0124 0.0247 0.1497 1.2646 8.3487 0.5341 0.0124 0.025 Na2O 0.0355 0.3601 6.9225 0.0654 0.040 0.0056 0.0024 0.0114 0.0358 6.9137 1.3536 0.0056 0.0004 K2O 0.0001 0.0034 0.127 0.0001 0.065 9.9046 0.0013 0.0099 0.0077 0.1563 14.1545 9.9046 0.0001 V2O3 0.0002 0.0474 0.0303 0.0002 0.796 0.131 0.3999 0.0027 0.0002 0.131 0.2879 ZrO2 0.0325 0.0002 0.0121 0.0002 0.000 0.0021 0.0238 0.0002 0.0002 0.0021 0.0029 Total 97.69 96.95 96.35 95.1496 95.39 93.48 89.7703 98.0204 102.39 98.06 97.38 93.48 96.14 No. Oxygens 12 4 8 18 3 11 4 6 12 8 8 11.00 3.00 Si 2.973744264 0.0007584 2.607005788 4.9981211 0.004 2.8 0.001596 1.892123 2.977082 2.60254 2.974697 2.8003632 0.001482 Ti 0.001888937 0.0001538 0.00057752 0.0010625 0.407 0.261 7.98E-06 0.004365 0.001671 0.001008 7.11E-06 0.260573 1.012061 Al 1.991758202 1.9487132 1.373164607 3.9395928 0.003 1.202 0.009311 0.190759 2.029308 1.378838 1.021159 1.201698 9.14E-06 Cr 0.001966947 0.0052814 7.35811E-06 0.0014371 0.002 0.002 0.005516 0.000872 0.001286 0.000936 0.001442 0.002007 4.09E-06 Fe2+ 1.653403422 0.4258332 7.78259E-06 0.2567934 2.093 0.866 3.944934 0.964679 2.000011 0.003028 0.000925 0.865573 0.918877 Mn2+ 0.041247601 4.811E-06 0.000465063 1.759E-05 0.003 0.006 4.49E-06 0.008535 0.049663 7.75E-06 8.01E-06 0.005992 0.003829 Mg 1.239294203 0.4114851 0.00018038 1.8266025 0.032 1.7 0.000245 0.939194 0.840464 2.05E-05 1.41E-05 1.69954 0.03948 Zn 0.001675062 0.2182539 0.002865296 1.534E-05 0.000 0.006 0.001069 0.000169 1.13E-05 6.75E-06 6.98E-06 0.006292 0.000976 Ca 0.117329848 6.086E-06 0.403271151 2.226E-05 0.003 0.001 0.001403 0.006318 0.10343 0.409003 0.027043 0.001013 0.000693 Na 0.005384648 0.0198288 0.624543152 0.0131701 0.003 0.001 0.000247 0.000871 0.005299 0.612921 0.124024 0.000828 2.01E-05 K 9.97998E-06 0.0001232 0.007538829 1.325E-05 0.003 0.963 8.79E-05 0.000498 0.00075 0.009117 0.85332 0.963159 3.3E-06 V3+ 1.25449E-05 0.0010793 0.001130446 1.666E-05 0.023 0.008 0.016999 0 0 9.9E-05 7.58E-06 0.008006 0.00597 Zr 0.001239803 2.77E-06 0.000274552 1.013E-05 0.000 0 0.000615 0 0 4.46E-06 4.61E-06 7.81E-05 3.66E-05 Total Cations (S) 8 3 5 11 3 8 4 4 8 5 5 8 3 Xmg (mg/(fe+mg)) 0.42842162 0.4914321 0.958639093 0.8897144 0.015 0.663 6.21E-05 0.493307 0.295888 0.006708 0.01501 0.662559 0.041196 Xmg(divalent) 0.405933326 0.3898178 0.000443424 0.8879082 0.015 0.659 6.21E-05 0.489445 0.280755 4.96E-05 0.000503 0.659143 0.040961 X(Fe) (multi mineral) 0.57157838 0.5085679 0.041360907 0.1102856 0.985 0.337 0.999938 0.506693 0.704112 0.993292 0.98499 0.337441 0.958804 2
y(opx) 0.079 f(opx) 0.025
Table 6 3
Sample No. External Characteristics Internal textures/features Other distinguishing features 207Pb/206Pb age of CL domains BH12 100-350 μm; subhedral to anhedral; Two dominant types: • Weakly to moderately luminous homogenous Weakly luminescent cores: 1632±11 prismatic and stubby or ovoid shapes with 1) Subhedral, dark to weakly luminescent cores surrounded by rims or patches and lobes cross cut zoning. Ma subrounded crystal face terminations; thick, blurred zoning. • Strongly luminescent rims (20-40μm) common. Oscillatory Zoning: 1641.7±8.0 Ma Aspect ratios between 2:1 and 6:1. 2) Blurred, chaotic oscillatory zoned grains • Recrystallisation fronts also seen within the Luminescent rims: 1644±10 Ma interior of the grains. BH15 75um to 1.1mm;prismatic and stubby, or Three dominant zircon types: • Thick (20-60 μm) grey to strongly luminescent Homogenous cores: 1637±11 Ma elongate to tabular with sub rounded crystal 1) Blurred and convoluted oscillatory zoned grains rims on the majority of rims. Oscillatory zoning: 1632±15 Ma face terminations. The crystals are largely 2) Sector zoning preserved around oscillatory zoned or convoluted cores. • Interpreted as recrystallisation fronts which cross Luminescent rims: 1622.5±9.6 Ma wholly intact with minimal internal 3) Dark, mottled cores surrounded by ‘ghost zoning’. Cores are partly cut sector and oscillatory zoning. fracturing. adsorbed by homogenous weakly luminescent rims or occasionally ‘fir tree zoning’ within thickened rims surrounding cores. BH17 30- 450 μm; Length to width ratios 2:1 to Three dominant types: • Dark, rounded inclusions and multiple cores also Homogenous Cores: 1577±16 4:1; Elongate to tabular in shape with sub 1) Approximately half of the zircons are very weakly luminescent and appear in some of the larger zircons. Convoluted Cores: 1578±10 Ma rounded crystal face terminations; A small % homogenous, with no oscillatory zoning preserved. Blurred and patchy • Very occasionally, weakly luminescent rims were Oscillatory Zoning: 1601±17 Ma of angular fragments and stubby, prismatic zones of varying luminescence or small, anhedral xenocrystic cores are developed on the grains and these were Weakly luminescent rims: 1578±10 grains. occasionally preserved. Recognisable rims are rarely developed on these preferentially targeted for U-Pb analysis. Ma grains. 2) A small number of grains picked in this sample do preserve some oscillatory zoning, either as patches or xenocrystic cores within the crystal; or as zoned rims surrounding convoluted cores. 3) Chaotic, blurred internal textures are extremely common creating multiple domains of varying luminescence within a single crystal. BH19 50 and 200 um; Variable external The internal morphology of these zircons is extremely chaotic and diverse. • Strongly luminescent rims and recrystallised Convoluted Cores: 1621±12 Ma morphologies; anhedral to subhedral grains 1) Patchy domainal zoning, similar to that described by Corfu et al. 2007 is patches and lobes often cross cut sector zoned Luminescent rims: 1607±17 Ma usually prismatic or ovoid in shape; Length extremely common regions. to width ratios 2:1 to 4:1; Subrounded to 2) Homogenous, strongly luminescent grains. • Local recrystallisation is common around subangular crystal face terminations; Many 3) Some distorted oscillatory zoning present, but very rare. xenocrystic cores within the zircons. of the grains are angular fragments of larger • A number of the zircon crystals show evidence of grains. having undergone metamictization, including fragmented and cracked crystal structures with poor CL response. BH22 150 and 500 μm; Length to width ratios of Two dominant types: • Many grains also feature strongly luminescent between 2:1 and 5:1; Crystal face 1) Tabular, elongate zircons are extremely common . The majority of these recrystallisation fronts which cross cut internal Homogenous cores: 1597±11 Ma terminations are subrounded to rounded. zircons contain a very strongly luminescent centre which mirrors the same zoning and darker, homogeneous cores in some of Luminescent domains: 1592±19 Ma morphology as the external shape of the zircon. the crystals. Weakly luminescent rims: 1598.2±8.0 2) Weakly luminescent zircons, often completely homogenous or with • Luminescent rims are not seen in this type of patches of chaotic, convoluted sector zoning. A small number of these sample, with rims mainly taking the form of relict, zircons contain anhedral xenocrystic cores which themselves show blurred zoning or homogenous light grey zircon. oscillatory zoning, or convoluted zoning.
Table 8a
4
Sample No. External Characteristics Dominant internal textures Other distinguishing features 207Pb/206Pb age population BH08 50um and 250 μm; Aspect ratio between 3:1 Subangular elongate or subrounded spherical xenocrystic cores • A light grey or dark grey rim is a common Large peaks: 1756±8.5 Ma; and 2:1; Predominantly stubby to elongate; are a common feature in this rock. These cores tend to fit the feature on these grains, usually allowing for 1847.4±6.3 Ma (n=38, MSWD=0.46). Rounded to subrounded crystal faces characteristics of one of three categories; clear differentiation between growth zones. Smaller peaks: 1643±15 Ma; 1958±12 terminations; Small % grains are subangular 1) Low luminescence, homogenous cores with sub angular to sub Ma; 2149±21 Ma; 2255±16 Ma; fragments of larger grains. rounded boundaries. 2319±14; 2409±16 Ma; 2469±20 Ma; 2) Oscillatory zoned or partially zoned elongate to acicular 2870±23 Ma; xenocrystic cores. Youngest concordant grain: 1287 ±21 3) Strongly luminescent convoluted and patchy subrounded to Ma subangular cores. BH16 50-350 μm; Extremely variable external The external and internal characteristics of these zircon grains • Rims are a common feature in this sample morphologies; Elongate to acicular in shape were also extremely capricious. Grains usually fell into one of and vary in luminescence. Large peaks: 1652.6 ± 4.2 Ma; with subrounded to subangular crystal face three characteristic groups: • Detrital cores are readily identifiable by 1728±5.8 Ma terminations; ‘tear drop’ shaped with truncation between more clearly zoned cores Smaller peaks: 1576±22Ma; 1836±22 subrounded to rounded terminations; length 1) Oscillatory zoned xenocrystic cores. Zoning is usually and homogenous rims. Ma; 2320 ±24Ma; 2434±24Ma; 2003 to width ratios 3:1 to 5:1. convoluted or thickened. Thin (<10μm) to thick rims (20-40μm) ±19Ma; 2103±18Ma. Youngest are commonly bound these cores. Recrystallisation fronts truncate blurred concordant zircon: 1573±19Ma 2) Weakly luminescent homogenous grains with no oscillatory zoning. Not restricted to the crystal distinguishable core or rim. face boundaries, happens around inclusions or 3) Euhedral, broken fragments which feature chaotic internal centre of the grain. textures and are largely fractured and metamict. Highly variable internal luminescence within sector zoning or relic oscillatory zoning. I0508 50 and 300 μm;Length to width ratios 2:1 and 1) Oscillatory zoned cores, partially recrystallised resulting in • An extremely common feature of this Large broad peaks: 1593.7±20 Ma, 4:1; Subrounded to rounded crystal face thickened, blurred domains (Reference) sample is the appearance of dark black-brown, 1626.3± 14 Ma 1666±18 Ma terminations. Elongate to prismatic; Often 2) Homogenous, xenocrystic cores. Homogenous cores are either euhedral to subhedral inclusions. Smaller peaks: 1781 ±26 Ma ; metamict and corroded along some strongly luminescent or very weakly luminescent. Strongly • Rims of varying luminescence are also 2140±25 Ma; 2330±15 Ma; 2416 ±17 boundaries, resulting in irregular and abstract luminescent cores are occasionally surrounded by weakly common across the sample. Ma; 2488 ±24 Ma; 2573 ±18 Ma ; shapes; Smaller, ovoid grains are also luminescent, thin (~20 um) rims. In these grains fracturing often 2636 ±23 Ma; 2769 ±17 Ma frequent. propagates from the cores outwards to the rims. This could be Youngest concordant zircon: 1575 interpreted as expansion within the luminescent, U rich domains ±18 Ma resulting in cracking and fracturing into the adjacent, more brittle U poor domains
Table 8b
5
Sample no. No. of analyses Physical characteristics Internal features Textural locations BH08 29 analyses on 26 grains 20-50 μm, irregular shapes, subrounded. Some BSE imaging reveals small (<5 μm) domains of chemical Within garnet grains (G1). grains display a large number of pervasive zonation and distinct growth domains. Within garnet-ilmenite symplectites (G2). fractures and cracks, and are partly resorbed at Within matrix of sillimanite, quartz, oxides. grain boundaries Within retrograde orthoamphibole and sillimanite.
BH09 45 analyses on 41 grains 20 and 70 μm in size, typically subhedral to BSE imaging revealed some variation in monazite Within garnet grains (G1). anhedral irregular shaped grains chemistry but no distinctive growth zones (i.e. cores Within garnet-ilmenite symplectites (G2). and rims). Within matrix of sillimanite, quartz, oxides. Within retrograde orthoamphibole and sillimanite.
BH16 34 analyses on 30 grains Monazites are between 30 and 100μm in size and BSE imaging reveals that there is very little chemical Just over half of the grains ablated were located within are either well rounded (in garnets) or are cuspate, variation in the monazites. euhedral porphyroblasts of garnet irregular grains within the matrix of the rock. Within the matrix (quartz, k-feldspar, plagioclase, ilmenite) Matrix monazites are porous and patchy along the boundaries, suggesting alteration. Most grains are well preserved with very little fracturing.
BH10 40 analyses on 18 grains Monazites ranged from 50-350 um in size and Careful analysis of BSE images reveal that some Grains were picked and mounted in epoxy resin for were typically a distinct brownish-pink colour. monazites preserved multiple growth domains, which analysis. Grains are subhedral to anhedral fragments which are often preserved as very small (5-10um) patches or were highly varied in shape. zones on the edges of the crystals. No predictable pattern could be determined from the domains, and as such analyses were taken from homogenous areas within the monazites.
Table 9
6
Sample ΣREE (ppm) Location LREE (Smn/Lun) HREE (Lun/Smn) Ce/Ce* Eu/Eu* BH15 ~424–2950 Cores 0.55–40.7 11.09-60.69 1.35-11.2 0.17-0.49 Avg. = 7.90 Avg=24.84 Avg=4.61 Avg=0.31
Rims 0.4- 24.57 3.49-28.29 1.06-30.48 0.2-0.41 Avg= 10.37 Avg=23.37 Avg= 13.97 Avg=0.31
Rims (Red) 0.28-1.34 3.79-15.4 1.06-1.16 0.25-0.41 Avg=0.67 Avg=11.45 Avg=1.11 Avg=0.31
~504-5988 Cores (grey) 0.67-41.02 2.17- 49.14 1-51 0.06-0.14 Avg.=13.52 Avg=22.45 Avg= 9.22 Avg=0.07 BH17 Rims (red) 0.12-0.56 4.15-18.42 0.84-1 0.06-0.8 Avg=0.32 Avg= 11.71 Avg= 11.71 Avg=0.16
Rims 1.35- 9.84 13.36-34.36 1.93-23.01 0.06-0.13 Avg= 7.09 Avg=29.00 Avg= 9.22 Avg= 0.09
BH08 ~679-4655 Cores (red) 0.3-108 4-57 0.9-5.1 0.06-0.63 Avg=1.38 Avg=9.37 Avg= 1 Avg=0.38
Cores (Grey) 0.3-108 4-57 09-5.1 0.06-0.63 Avg= 36.24 Avg=24.45 Avg=3.81 Avg=0.14
Rims 1.7- 15 6-15 0.88-12.43 0.1-1.1 Avg= 11.24 Avg=11.24 Avg=4.35 Avg=0.25
BH16 ~34-3914 Cores (Grey) 0.56-33.56 10-59 1.06-7.23, 0.05-0.42 Avg=15.29 Avg=30.62 Avg=1.98 Avg=0.139
Cores (Red) 0.48-3.57 19.46-32 1-2.29 0.08-0.25 Avg=1.59 Avg=24 1.484 Avg=0.15
Rims (Blue) 0.39-107 3.06-4.32 0.98-1.4 0.03-0.08 =1.60 Avg=3.9 Avg=1.1 Avg=0.05 7
Rims (Black) 0.3-107 3.06-55.6 0.98-11.2 0.03-0.25 Avg=18.1 Avg=35.9 Avg=2.95 Avg=0.18
I0508 ~1138-6960 Cores 3.4-102.1 0.45-5.9 0.92-1.7 0.05-0.93 Avg=24.9 Avg=2.8 Avg=1.2 Avg=0.48
Rims 0.72-7.16 2.3-18.9 0.82-1.36 0.09-0.86 Avg=3.43 Avg= 3.43 Avg=1.16 Avg= 0.57
Table 11
Sample Sample N Hf176/Hf177 2 S.E. Lu176/Hf177 Yb176/Hf177 U/Pb AGE Hfi epsilon 1s T(DM) T(DM) crust Hf Chur (t) Hf DM (t) BH08 BH_12_43 0.28163937 6.14239E-05 0.00171071 0.100571566 1751 0.281583 -3.10 2.1 2.30 2.60 0.281670 0.281976 BH08 bh_8_10_32 0.281449684 4.87919E-05 0.000723114 0.045542523 1758 0.281426 -8.52 1.707716 2.50 2.93 0.281665 0.281971 BH08 bh_8_20_69 0.281520871 6.57634E-05 0.000965896 0.058808705 1839 0.281487 -4.49 2.30172 2.42 2.75 0.281614 0.281911 BH08 bh_8_22_78 0.281565713 3.63441E-05 0.000568194 0.034257008 1845 0.281546 -2.27 1.272044 2.34 2.62 0.281610 0.281907 BH08 bh_8_21_75 0.281376043 5.6424E-05 0.000601344 0.037340783 1864 0.281355 -8.62 1.97484 2.59 3.02 0.281598 0.281893 BH08 bh_8_1_1 0.281426028 3.29422E-05 0.000495591 0.03026702 1866 0.281408 -6.67 1.152976 2.52 2.90 0.281596 0.281891 BH08 bh_8_33_122 0.281518553 3.96368E-05 0.000880122 0.049929879 1871 0.281487 -3.76 1.387286 2.42 2.73 0.281593 0.281887 BH08 BH_34_127 0.28158098 3.79717E-05 0.000816147 0.054902531 1951 0.281551 0.32 1.3 2.33 2.55 0.281542 0.281828 BH08 bh_8_23_85 0.281544781 5.40476E-05 0.000974876 0.056863171 1974 0.281508 -0.67 1.891667 2.39 2.62 0.281527 0.281811 BH08 bh_8_7_22 0.281481433 6.09858E-05 0.00090483 0.057928506 2000 0.281447 -2.25 2.134502 2.47 2.74 0.281510 0.281792 BH08 BH_13_44 0.281285016 4.73098E-05 0.001039856 0.060752713 2116 0.281243 -6.84 1.7 2.75 3.10 0.281436 0.281705 BH08 BH_13_47 0.281490215 8.47165E-05 0.001237742 0.083875914 2156 0.281439 1.05 3.0 2.48 2.66 0.281410 0.281675 BH08 bh_8_27_104 0.281404085 7.14068E-05 0.000709819 0.042029759 2246 0.281374 0.78 2.499239 2.56 2.75 0.281352 0.281608 BH08 BH_15_51 0.281238832 6.39587E-05 0.000665625 0.03942299 2253 0.281210 -4.87 2.2 2.78 3.09 0.281347 0.281603 BH08 bh_8_27_102 0.281318577 4.45482E-05 0.00107883 0.067120909 2279 0.281272 -2.09 1.559186 2.71 2.94 0.281330 0.281584 BH08 BH_5_16 0.281237156 4.87238E-05 0.000367992 0.022068389 2281 0.281221 -3.84 1.7 2.77 3.05 0.281329 0.281582 BH08 bh_8_11_36 0.281051508 4.63435E-05 0.000984711 0.058871014 2399 0.281006 -8.76 1.622022 3.06 3.43 0.281253 0.281494 BH08 BH_4_12 0.281652594 5.70166E-05 0.00237925 0.155647555 2401 0.281544 10.38 2.0 2.33 2.29 0.281252 0.281492 BH08 bh_8_23_87 0.281246117 4.30991E-05 0.000517514 0.031397637 2440 0.281222 -0.15 1.508469 2.76 2.95 0.281226 0.281463 BH08 BH_8_26 0.281355339 5.04269E-05 0.001478432 0.088395584 2516 0.281284 3.82 1.8 2.68 2.77 0.281177 0.281406 BH08 BH_11_33 0.280973627 5.09466E-05 0.001162369 0.072059237 2868 0.280910 -1.36 1.8 3.18 3.35 0.280948 0.281141 BH16 BH_28_72 0.281668 6.01E-05 0.002473063 0.141138328 1610 0.281593 -5.93 2.1 2.31 2.66 0.28176 0.28208 8
BH16 BH_24_63 0.281668 7.57E-05 0.001685099 0.113226256 1637 0.281615 -4.52 2.6 2.26 2.6 0.281743 0.282061 BH16 BH_10_26 0.281757 6.59E-05 0.001642054 0.096065858 1646 0.281705 -1.13 2.3 2.14 2.4 0.281737 0.282054 BH16 BH_11_28 0.281742 4.69E-05 0.001794712 0.117661897 1654 0.281686 -1.64 1.6 2.16 2.44 0.281732 0.282048 BH16 BH_5_17 0.281727 5.45E-05 0.002213506 0.144423087 1671 0.281657 -2.27 1.9 2.21 2.49 0.281721 0.282035 BH16 bh_16_19_47 0.281678 5.01E-05 0.001830194 0.109945615 1671 0.28162 -3.57 1.752859 2.26 2.57 0.281721 0.282035 BH16 BH_20_55 0.28169 5.47E-05 0.002201918 0.145042181 1674 0.281621 -3.5 1.9 2.26 2.57 0.281719 0.282033 BH16 BH_2_5 0.281664 5.48E-05 0.002368957 0.156819404 1686 0.281589 -4.36 1.9 2.31 2.63 0.281711 0.282024 BH16 bh_16_30_73 0.281651 4.32E-05 0.00092957 0.058475546 1701 0.281622 -2.85 1.512393 2.24 2.55 0.281702 0.282013 BH16 BH_23_60 0.281699 3.90E-05 0.001634609 0.107401835 1709 0.281646 -1.81 1.4 2.22 2.49 0.281697 0.282007 BH16 BH_7_22 0.281709 5.33E-05 0.001329692 0.087763409 1721 0.281665 -0.84 1.9 2.18 2.44 0.281689 0.281998 BH16 BH_38_97 0.281307 5.48E-05 0.000299456 0.021710709 1922 0.281296 -9.4 1.9 2.67 3.11 0.28156 0.28185 BH16 BH_1_2 0.281284 4.66E-05 0.000704213 0.043831266 2103 0.281256 -6.68 1.6 2.73 3.08 0.281444 0.281715 BH16 BH_23_57 0.281327 4.72E-05 0.001326542 0.085015759 2105 0.281274 -6 1.7 2.71 3.04 0.281443 0.281714 BH16 bh_16_64_123 0.28143 4.96E-05 0.0010315 0.065843965 2140 0.281388 -1.16 1.734633 2.55 2.78 0.28142 0.281687 BH16 BH_56_118 0.281637 4.51E-05 0.001805661 0.119594803 2252 0.28156 7.53 1.6 2.31 2.35 0.281348 0.281604 BH16 BH_35_89 0.281318 3.83E-05 0.000825321 0.050267522 2315 0.281281 -0.92 1.3 2.69 2.9 0.281307 0.281557 BH16 BH_28_67 0.281189 5.15E-05 0.00100285 0.06706123 2401 0.281144 -3.84 1.8 2.88 3.14 0.281252 0.281492 BH16 BH_31_78 0.280996 4.89E-05 0.000883681 0.056482273 2589 0.280952 -6.31 1.7 3.13 3.43 0.28113 0.281351 I0508 bh_i_4_74 0.281555 3.74001E-05 0.000703034 0.046184751 2146 0.281526 3.91 1.309003 2.36 2.48 0.281416 0.281683 I0508 bh_i_25_58 0.281095 4.13073E-05 0.000729094 0.045298857 2547 0.281060 -3.45 1.445757 2.98 3.23 0.281157 0.281383 I0508 bh_i_27_69 0.281076 3.98693E-05 0.001001178 0.061205611 2635 0.281025 -2.64 1.395425 3.03 3.25 0.281100 0.281317 I0508 BH_I_1_2 0.281091 5.871E-05 0.000970167 0.060986805 2338 0.281048 -8.69 2.1 3.01 3.38 0.281292 0.281540 I0508 BH_I_1_6 0.281029 4.38113E-05 0.001629223 0.096565277 2301 0.280957 -12.76 1.5 3.14 3.59 0.281316 0.281567 I0508 BH_I_1_79 0.281549 4.65308E-05 0.00099698 0.061176633 1668 0.281518 -7.29 1.6 2.38 2.79 0.281723 0.282038 I0508 BH_I_4_74 0.281553 3.86885E-05 0.000689609 0.045546512 2146 0.281525 3.85 1.4 2.36 2.49 0.281416 0.281683 I0508 BH_I_7_19 0.281585 3.98588E-05 0.000823142 0.051776146 1640 0.281560 -6.43 1.4 2.32 2.72 0.281741 0.282058 I0508 BH_I_9_23 0.281583 4.29622E-05 0.001168216 0.075525423 2498 0.281527 12.03 1.5 2.35 2.27 0.281189 0.281420 I0508 BH_I_10_77 0.281156 4.20253E-05 0.001219989 0.078501087 2324.4 0.281102 -7.10 1.5 2.94 3.27 0.281301 0.281550 I0508 BH_I_10_79 0.281358 3.59895E-05 0.00225583 0.129977412 2309 0.281259 -1.86 1.3 2.74 2.95 0.281311 0.281561 I0508 BH_I_10_86 0.281287 4.45819E-05 0.001502241 0.099793879 2345 0.281219 -2.43 1.6 2.78 3.01 0.281288 0.281534 I0508 BH_I_11_33 0.281099 5.84106E-05 0.001109776 0.067163976 2416 0.281048 -6.90 2.0 3.01 3.33 0.281242 0.281481 I0508 BH_I_13_38 0.280918 4.89479E-05 0.001494262 0.093773436 2232 0.280854 -18.01 1.7 3.29 3.85 0.281361 0.281619 9
I0508 BH_I_14_40 0.281655 3.61913E-05 0.001322032 0.07686264 1748 0.281611 -2.16 1.3 2.26 2.54 0.281672 0.281979 I0508 BH_I_15_92 0.281512 4.13219E-05 0.0010074 0.06269722 2637 0.281461 12.91 1.4 2.44 2.33 0.281098 0.281315 I0508 BH_I_16_96 0.281596 6.87097E-05 0.000975857 0.061671336 1663 0.281565 -5.72 2.4 2.32 2.69 0.281726 0.282041 I0508 BH_I_19_46 0.280898 3.12665E-05 0.000678829 0.044646164 2769 0.280862 -5.36 1.1 3.24 3.51 0.281012 0.281216 I0508 BH_I_22_54 0.281559 4.66655E-05 0.00065603 0.044301477 1634 0.281539 -7.32 1.6 2.35 2.77 0.281745 0.282063 I0508 BH_I_22_55 0.28153 4.47326E-05 0.001096964 0.062159707 1575 0.281497 -10.11 1.6 2.42 2.89 0.281782 0.282106 I0508 BH_I_27_67 0.281171 9.6922E-05 0.001863615 0.116685756 2133 0.281095 -11.72 3.4 2.97 3.40 0.281425 0.281693 Table 12
Krishna Province North Dharwar Craton East Antarctica North China Craton References Australian Craton
U-Pb age εHf TDM (Ga.) U-Pb age (ca.) εH TDM U-Pb εHf TDM U-Pb age εHf TDM U-Pb age εHf TDM (ca.) Ma Ma f age (ca.) (ca.) Ma (ca.) Ma Ma 2870 -1.3 3.35 2850; 2883 2900- 0 to +5 3.2-3.5 Carson et al. (2002); Zhai & Santosh 2700 (2011) 2770 -5.3 3.51 2725 2741; 2790 2900- 0 to +5 3.2-3.5 Carson et al,. (2002); Zhai & Santosh 2700 (2011); Horie et al., (2011) 2640 - 3.2 2694 2658 - 2626; 2637 Rogers et al., (2007); Carson et al,. 2.64 2613 (2002); Bierlein et al., (2008) 2580 -4 3.3 2540 2550- 1.36 2.7- 2520-2580 2500- +4 to +9 2.7-2.4 Hokada et al., (2003); Jaynanda et al. 2560 to 2.9 2600 2000; Zhou et al. 2011; Druppel et al. 5* (2009) 2450 -1 3 2440-2485 2450; 2484 Carson et al. (2002) 2400 -6 3.3 2418 2387; 2410- 2400 +1 2.8 Asami et al., (2001); Zheng et al., 2430 (2004); Horie et al., (2011) 2330 -1 or 3 or 3.3 2317 2365 2380 Halls et al., (2007) -9 2252 7.5 2.3 2211-2252 2221- 2241 Zhao & Bennett (1994) 2209 2250 -2.5 2.9 2211-2252 2221- 2241; 2267 Horie et al., (2011) 2209 2150 2 2.6 2181- 2154; 2195 2116- -0.5 to 9.4 2.5-2.9 Suzuki et al. 2008; Yin et al 2011 2171 2151 10
2020 - 2.7 2038 Zhao & Bennett (1994) 2.25 1950 0 2.6 1971; 1979 1960 -0.5 to 9.4 2.5-2.9 Suzuki et al. 2008; Yin et al 2011; Horie et al., (2011) 1850 -5 2.8 1860 1817- -10 1.9-3 1824; 1850 1850 Murthy 1987, Bhaskar Rao 1995; 1890 to 1 Anand et al. 2003; Lanyon et al. (1993); Horie et al., (2011) 1750 -2 2.6 1750 1754 ± 16 1750- -4 to +7.5 2.4-2.3 & 2.9- Zhang et al., (2007) 1680 2.7 1650-1700 -3.5 2.6 1557 Owada et al., (2003) Table 1
21. Figures
Figure 9
2
Bonnie J. Henderson
Appendix I
18. Analytical procedures
18.1 Zircon geochronology: Sample preparation and LA-ICP-MS operating procedures
Zircon extraction and preparation was undertaken at the University of Adelaide. Samples chosen for zircon geochronology were crushed using a jaw crusher and then ground in a tungsten carbide mill for a period of 3-5 seconds. Samples were then sieved using a 75μm and
425μm in order to retain a size fraction between 75-425μm. Traditional panning techniques separated the zircon fraction from lighter minerals, and following this, magnetic grains were removed using conventional magnet techniques and Frantz Isodynamic separation. The remaining fraction was put through heavy liquid separation using methylene iodide (Density
~2.85 g/ml) in order to separate zircons from remaining lighter minerals such as quartz or feldspars. Approximately 200 zircon grains per sample were randomly handpicked and mounted in epoxy resin. The grains were then ground down to half their width. BH08 was processed in a different manner. Samples were crushed and put through separation techniques but no zircons were returned. The fines were sent to Minsep Laboratories in Denmark, WA where ~150 zircons were recovered.
Prior to analysis, epoxy mounts were imaged at Adelaide Microscopy, located on the
Adelaide University campus, using a Phillips XL20 SEM with attached Gatan cathodoluminescence (CL) detector. This technique allowed for the identification of internal chemical zonation, or domains within the zircon grains. A beam accelerating voltage of 12 kV, combined with a spot size of 7 were the parameters used to obtain these images.
U-Th-Pb analysis of zircons was conducted at Adelaide Microscopy using an Agilent 7500cs
ICPMS, coupled with a New Wave 213 nm Nd- YAG laser. Ablation was undertaken in helium atmosphere following similar methods to those prescribed by Payne et al. (2008;
2010). A beam diameter of between 25 and 30μm was used, as dictated by what was considered appropriate for the grain size. Other parameters used included a repetition rate of 5
Hz and laser intensity of 75%.
The total acquisition time for each analysis was 100 seconds, consisting of 25 seconds of background measurement, 5 seconds for beam and crystal stabilisation with the shutter closed and 70 seconds for sample ablation. Dwell times for isotope measurements were 10ms, 10ms,
15ms, 30ms and 10ms for 204Pb, 206Pb, 207Pb, 208Pb, 232Th and 238U respectively.
Common Pb (204) cannot be measured with the LA-ICPMS due to Hg interference with the
204 mass peak (Payne et al. 2008). However, 204Pb was monitored throughout all analyses in order to identify and subsequently omit analyses which displayed substantial amounts of common Pb.
18.2 Monazite geochronology: Sample preparation and LA-ICP-MS operating procedures
Insitu U-Pb analysis of monazites was also conducted at Adelaide Microscopy, also using the
Agilent 7500cs ICPMS coupled with the New Wave 213 nm Nd-YAG laser. A spot size of 15
μm, repetition rate of 5 Hz and laser intensity of 75% was used for all monazite analyses, with an exception for BH10 where the parameters were 5 Hz, 75% and a spot size of 20um. A forty second gas blank was measured prior to 60 seconds of monazite sample ablation.
Similarly to zircon analysis, the laser was fired for ten seconds with the shutter closed prior to ablation.
Analytical techniques for U-Pb isotopic dating of monazite grains follow those of Payne et al. (2008). A detailed explanation of the methods followed is included in Appendix 1. Insitu monazite grains were identified and imaged on thin sections for samples BH08, BH09 and
BH16, using the Phillips XL30 SEM with a Backscattered Electron detector (BSE). This technique allows for the textural relationship of the monazite grains with other minerals to be recorded. Monazite grains from sample BH10 were extracted and mounted as per the methods described in Section 7.1. The parameters used for imaging monazites were a beam intensity of
12 kV and a spot size of 5.
U-Pb fractionation was corrected using the documented standard Madel (Payne et al. 2008), in conjunction with the in-house standard 222 (Maidment 2005) which was used to monitor ongoing accuracy of the laser. Data reduction was completed using GLITTER software (E.
Van Achterbergh 2001). Conventional concordia plots and dischords were generated using
Isoplot/Ex 3.00. Errors shown on the concordia diagrams and quoted in the data tables are at the 2σ level. The weighted average 206Pb/238 U age for Madel is 516.2 ± 2.0 (n = 51, MSWD =
0.92), and the weighted average 206Pb/238U age for 222 is 455.6 ± 5.6 Ma (n = 16, MSWD =
1.6). Concordia diagrams, probability density plots and weighted average plots for samples
BH08, BH09, BH10 and BH16 are shown in Figures XXX.
18.3 Trace element (REEs) operating procedures and data reduction
Trace element analysis of zircon mounts used for geochronology was also performed at
Adelaide Microscopy using an Agilent 7500cs ICPMS equipped with a New Wave 213nm
Nd-YAG laser. Approximately 40 analysis locations were selected from concordant core and rim domains for each of the five samples. Zircon analyses were performed using a beam diameter of 50 um, repetition rate of 5Hz and a laser intensity of 75% for all samples but
BH15 where a beam diameter of 80um was used. Acquisition time for trace element data was
100 seconds in total, involving 30 seconds of background measurement, 10 seconds for beam and crystal stabilisation with the shutter closed, and 60 seconds for sample ablation. NIST
610 glass standard was used to calibrate the laser (Pearce et al. 2007), whereas internal calibration was conducted using measurements of 178Hf in zircon obtained via EPMA. Hf data was also obtained at Adelaide Microscopy using the same methodologies described in section
5 for mineral chemistry. Traverses across the selected domains were conducted in order to produce a representative Hf value for internal calibration. Data reduction was then completed using GLITTER software (Van Achterbergh et al. 2001). REE patterns are chrondrite normalised to values given by McDonough and Sun (1989). Chrondrite normalised spider diagrams were produced for results and are displayed in accordance to the CL domains targeted to identify any REE partitioning between individual domains.
18.4 Ti in zircon thermometry overview
The titanium content of zircon is now well documented as a potential indicator for zircon crystallisation temperature. Ti enters the zircon lattice in homovalent replacement of Zr4+ or
Si4+, and does not rely upon the availability of other charge compensating ions (Watson &
Harrison 2005). This study utilises the Ti-in-zircon thermometer of Watson and Harrison
(2005) and Watson and Ferry (2007). The thermometer was calibrated experimentally using the Ti contents of natural and synthetic zircons with known crystallisation temperatures, verified autonomously by independent geothermometers. Zircon is considered extremely retentive of its Ti chemical signature, and therefore is quite robust in terms of preserving a crystallisation temperature (Cherniak & Watson 2007). Ti diffuses considerably slower than
Pb, REEs and oxygen and should be retained under extreme geological conditions (e.g. high
P-T conditions, partial melting, and sedimentary processes) even when radiometric ages are lost (Cherniak & Watson 2001, 2007, Cherniak 2010).
Watson and Ferry (2007) revised the original Ti-in-zircon thermometer (Watson and Harrison
2005), recognising that the Ti content of zircon is dependent on the aSiO2 and aTiO2, as well as temperature. Consequently, new parameters were derived for the zircon thermometer allowing for it to be applied to rocks without quartz or rutile, or for those where the aSiO2 and aTiO2 are unknown (where a is activity). The revised thermometer was chosen for this study as the zircons analysed were crystallised in rocks where there is either; no rutile present, or the crystallisation conditions of the zircons are unknown (i.e. detrital zircons). The log-linear relationship between equilibrium Ti content (ppm), reciprocal temperature (K), and the activities of SiO2 and TiO2 are presented below:
Log (Ti zircon ppm) = (5.711 ±0.072) –(4800 ± 86)/ T(K)- log aSiO2 + aTiO2.
The equation above operates independently of pressure. The effect of pressure on the uptake of Ti in zircon has been assessed (Watson et al. 2006, Ferry & Watson 2007). For mid to lower crustal rocks, the effect on Ti uptake is very minimal. However, in rocks formed at very low pressures Ti uptake is increased, and conversely at very high pressures (eclogite facies)
Ti uptake is decreased. As such, in zircons where the crystallisation constraints are unknown, a ±1 Gpa uncertainty introduces an additional error of ~ 50C (Ferry & Watson 2007).
Additionally, using the thermometer on out-of-context zircons involves estimating the aTiO2.
However aTiO2 is to be considered to fall over a small range between 0.6 and 1 in silicic melts, and misrepresenting the activity of TiO2 will rarely underestimate crystallisation temperatures by more than ~50 C (Hayden & Watson 2007).
As has been shown, temperature range estimates provided by this study are largely based on the average Ti content and the 1 sigma detection errors for each analysis. The final estimates produced include the effects of these uncertainties, along with 2 sigma internal calibration errors of the thermometer, and the arbitrary pressure uncertainty of ±1 Gpa.
18.5 Lu-Hf operating procedures and data reduction
Zircon mounts prepared for U-Pb LA-ICPMS analysis for samples BH08, BH16 and I0508 were also used for insitu Lu/Hf isotopic studies undertaken with LA-MC-ICPMS at Waite campus (CSIRO), Adelaide. Methods follow that of Teale et al. (2011). Only zircon grains which produced U-Pb ages with concordance between 90-110% were selected. Ablation targeted the same CL domain as was used for U-Pb LA-ICPMS geochronology; most analyses were directly over the top of the previous ablation or adjacent to the previous analysis where the CL domain was large enough. Zircons were ablated with a New Wave UP-
193 Excimer laser (λ=193nm), where parameters for ablation were 4ns pulse length, 5 Hz and
2 a spot size 50 µm. Laser fluence (energy per unit area) was maintained at ~10 J/cm . Zircons were ablated in a helium atmosphere, which was then mixed with argon upstream of the ablation cell. Analyses used a dynamic measurement routine with: Ten 0.524 second integrations on 171Yb, 173Yb, 175Lu, 176Hf(+Lu+Yb), 177Hf, 178Hf, 179Hf and 180Hf; one 0.524 second integration on 160Gd, 163Dy, 164Dy, 165Ho, 166Er, 167Er, 168Er, 170Yb and 171Yb, and, one 0.524 second integration of Hf Oxides with masses ranging from 187 to
196 amu. Measurements were made using a Thermo-Scientific Neptune Multi Collector ICP-
MS equipped with Faraday detectors and 1012Ω amplifiers. An integration interval of 0.232 seconds was employed during analysis. An idle time of 1.5 seconds was included between each mass change to allow for magnet settling and to negate any potential effects of signal decay. This measurement cycle is repeated 15 times to provide a total maximum measurement time of 3.75 minutes including an off-peak baseline measurment. This dynamic measurement routine is utilised to allow for the monitoring of oxide formation rates and REE content of zircon and provide the option to correct for REE-oxide interferences as necessary. Hf oxide formation rates for all analytical sessions in this study were in the range 0.1-0.07%.
This study follows the interference and mass bias correction procedures recommended by
Woodhead et al. (2004). Mass bias on Hf was corrected using an exponential fractionation law with a stable 179Hf/177Hf ratio of 0.7325. Yb isobaric interference on 176HF was corrected for by direct measurement of Yb fractionation using measured 171Yb/173Yb with the Yb isotopic values of Segal et al. (2003). These values were verified by analysing JMC 745 Hf solutions doped up with varying levels of Yb with interferences up to 176Yb/177Hf = ∼0.5. Lu isobaric interference on 176Hf was corrected using a 176Lu/175Lu ratio of 0.02655 (Vervoort et al., 2004), under the assumption that the mass bias behaviour of Lu is the same as that of
Yb.
Set-up of the system prior to ablation sessions was conducted using analysis of
JMC475 Hf solution and an AMES Hf solution. Confirmation of accuracy of the technique for zircon analysis was monitored using a combination of the Plesovice, Mudtank and QGNG standards. The average value for Plesovice for the analytical session was 0.282479
(2SD=0.000022, n=27). This compares to the published value of 0.282482 +/- 0.000013
(2SD) by Slama et al. (2008).
18.5 Sample selection and overview of Thermocalc
Metapelitic rocks are not abundant in the Ongole Domain, often occurring only as ‘rafts’ within the dominant meta-igneous bodies. They are generally diatexitic granulites with pervasive garnetiferous leucosomes, quartzites or occasional calc-silicate gneisses (Mukhopadhyay and Basak 2009).
The samples chosen quantified metamorphic analysis were selected from two separate locations in the Ongole Domain, in order to place spatial constraints on thermal evolution of the Ongole Domain. The sample, BH16, preserves a diverse mineral assemblage, is garnet bearing and contains documented metamorphic minerals which can be used to constrain the thermodynamic conditions experienced by the rocks. For this approach to be appropriate, it is essential that the samples selected were considered to represent a state of ‘equilibrium’ reached within the rock (Powell and Holland 2010). Detailed petrographic analysis concluded that the metamorphic minerals were in textural equilibrium and fulfilled this condition.
The bulk composition of BH16 was obtained through from whole rock chemistry completed by Genalysis Ltd, Adelaide. The method used to acquire the bulk compositions was lithium metaborate fusion, and analysis by Inductively Couple Plasma (Atomic) Emission Spectrometry (ICP-AES) and ICP-MS. During this process the bulk rock powder is mixed with metaborate and fused in an induction furnace, before being dissolved and prepared for analysis by ICP-MS and ICP-AES (see Payne et al. 2010). To quantify the amount of FeO in the rocks, titration (wet chemistry) was also performed by Genalysis in Perth.
The main tool for determining P-T conditions in a metamorphic rock is the application of thermodynamics (Powell and Holland 2010). P-T pseudosections are considered to be the most powerful method available, as they allow for the calculation of the optimal metamorphic conditions for a specific bulk rock composition. Pseudosections also provide a visual tool which can be used as an insight into the P-T path followed by a rock.
A P-T pseudosection for sample BH08 was deliberated using the software program THERMOCALC following methods described by Powell and Holland (1988, 1998, 1994, 2010). THERMOCALC (v. 3.26) is based on an internally consistent dataset, and using a given compositional input (bulk rock composition), it searches for mineral reactions involving the stable mineral assemblage (Winter 2010). THERMOCALC considers the activities of the end members of minerals to be variable, allowing them to overlap and react accordingly with other independent subsets (Winter 2010). The program ultimately calculates the optimal P-T conditions by use of the least squares method (X2), a statistically robust process which varies the positions of the phase reactions in accordance with their uncertainties and correlations (Holland and Powell 1994).
Appendix II
Zircon geochronology data BH08 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
1_1 5.009 0.06655 0.31842 0.00407 0.861345 1866.3 19.79 1782 19.89 95 1_2 5.09595 0.07327 0.32537 0.00467 0.861345 1857.8 18.59 1815.9 22.72 98 1_3 5.21575 0.0718 0.33177 0.00458 0.861345 1864.6 18.24 1847 22.15 99 1_4 5.70455 0.08344 0.34774 0.00503 0.861345 1941 18.95 1923.8 24.08 99 1_5 4.29731 0.05951 0.29254 0.00402 0.861345 1741.2 18.88 1654.2 20.07 95 3_6 4.64071 0.06305 0.30809 0.00417 0.861345 1787 18.69 1731.3 20.55 97 3_7 4.92444 0.0681 0.3239 0.0045 0.861345 1803.9 18.38 1808.7 21.89 100 3_8 9.77958 0.13765 0.42006 0.00597 0.861345 2546.6 16.71 2260.7 27.12 89 3_9 6.26733 0.08023 0.32642 0.0042 0.861345 2218.1 17.49 1821 20.43 82 4_10 5.12523 0.07306 0.32732 0.0046 0.861345 1857.3 19.29 1825.4 22.34 98 4_11 5.12294 0.07049 0.33105 0.00459 0.861345 1836 18.22 1843.5 22.21 100 4_12 8.72598 0.12745 0.40862 0.00602 0.861345 2401.4 16.99 2208.6 27.56 92 4_13 8.76028 0.11612 0.41198 0.00551 0.861345 2393.4 16.98 2224 25.14 93 5_14 5.3578 0.07897 0.32454 0.00477 0.84748 1952.9 18.61 1811.9 23.24 93 5_15 4.93895 0.07188 0.31441 0.00455 0.84748 1863.6 18.78 1762.4 22.32 95 5_16 7.75248 0.11111 0.3892 0.00555 0.84748 2281.8 17.74 2119.1 25.77 93 5_17 4.63118 0.06345 0.29061 0.00387 0.84748 1890.3 19.6 1644.6 19.31 87 6_18 5.1983 0.08219 0.32703 0.0049 0.84748 1885 21.7 1824 23.81 97 6_19 5.03645 0.07441 0.33164 0.00471 0.84748 1802.2 20.43 1846.3 22.79 102 7_20 5.25989 0.07645 0.33623 0.00488 0.84748 1855.9 18.34 1868.5 23.55 101 7_21 4.65192 0.06797 0.31028 0.00453 0.84748 1778.7 18.5 1742.1 22.3 98 7_22 6.24288 0.09375 0.3667 0.00545 0.84748 2007.4 18.66 2013.8 25.71 100 7_23 5.02938 0.07735 0.32389 0.00479 0.84748 1842.6 20.77 1808.7 23.32 98 8_24 5.21732 0.07502 0.33902 0.0048 0.84748 1826.2 19.18 1881.9 23.1 103 8_25 3.92409 0.05763 0.28169 0.00413 0.84748 1643.7 18.98 1599.9 20.77 97 8_26 10.61188 0.15183 0.46399 0.00665 0.84748 2516.8 16.87 2457.2 29.28 98 9_27 5.25837 0.07571 0.33746 0.00487 0.885821 1848.5 18.13 1874.4 23.49 101 9_28 5.28765 0.07793 0.33864 0.00496 0.885821 1852.4 18.73 1880.1 23.91 101 10_29 5.20549 0.0759 0.33727 0.00491 0.885821 1831.4 18.44 1873.5 23.68 102 10_30 3.61507 0.05316 0.25529 0.00374 0.885821 1673.8 19.12 1465.7 19.18 88 10_31 4.40873 0.06464 0.2966 0.00436 0.885821 1762.8 18.29 1674.4 21.7 95 10_32 4.64716 0.06734 0.31337 0.00453 0.885821 1758.6 18.6 1757.2 22.24 100 11_33 16.24174 0.23589 0.57392 0.00837 0.885821 2868.6 16.49 2923.9 34.3 102 11_34 7.54457 0.10769 0.36989 0.00527 0.885821 2322.4 17.71 2028.9 24.81 87 11_35 16.22173 0.23531 0.57392 0.00837 0.885821 2866.6 16.46 2923.9 34.27 102 11_36 9.52365 0.13636 0.4462 0.00638 0.885821 2399.8 17.59 2378.3 28.44 99 11_37 5.16695 0.07973 0.30939 0.00476 0.885821 1973.1 18.65 1737.7 23.43 88 12_38 8.59957 0.12746 0.41782 0.00621 0.885821 2338 17.55 2250.6 28.24 96 12_39 7.82658 0.11691 0.39274 0.00576 0.885821 2282.6 19.32 2135.5 26.64 94 12_40 10.25928 0.14318 0.46509 0.00653 0.885821 2455.6 17.15 2462 28.75 100 12_41 3.38515 0.0514 0.24425 0.00366 0.885821 1634.1 20.09 1408.7 18.94 86 12_42 5.7654 0.09148 0.33697 0.0051 0.860161 2016.2 21.32 1872.1 24.57 93 12_43 4.60463 0.06451 0.31179 0.0044 0.860161 1751 18.39 1749.5 21.6 100 13_44 6.84375 0.09808 0.37786 0.0053 0.860161 2116.3 19.23 2066.3 24.77 98 13_45 3.37105 0.04971 0.24665 0.00359 0.860161 1607.8 19.77 1421.2 18.56 88 13_46 5.41552 0.07848 0.3413 0.00494 0.860161 1881.2 18.57 1892.9 23.74 101 13_47 7.76917 0.1102 0.41922 0.00593 0.860161 2156.5 18.18 2256.9 26.95 105 14_48 5.03906 0.07166 0.32602 0.00448 0.860161 1833.9 20.2 1819.1 21.77 99 14_49 4.19491 0.06043 0.29744 0.00431 0.860161 1666.2 18.84 1678.6 21.42 101 14_50 10.7337 0.16365 0.4328 0.00666 0.860161 2651.6 17.32 2318.3 29.94 87 15_51 7.89035 0.12324 0.40262 0.0061 0.860161 2253.6 20.25 2181.1 28.06 97 15_52 5.4836 0.0784 0.35628 0.00511 0.860161 1826.1 18.58 1964.5 24.31 108 15_53 5.28445 0.07694 0.34722 0.00509 0.860161 1805.8 18.57 1921.3 24.37 106 15_54 5.03827 0.07607 0.32936 0.00496 0.860161 1815.2 19.41 1835.3 24.05 101 15_55 4.08953 0.05826 0.27735 0.00402 0.860161 1748 18.17 1578 20.26 90 16_56 5.2353 0.07608 0.33937 0.00491 0.932426 1830.6 18.98 1883.7 23.65 103 16_57 4.9041 0.06997 0.32272 0.00468 0.932426 1803.2 18.02 1803 22.83 100 16_58 4.92066 0.06977 0.30666 0.00439 0.932426 1901.5 18.01 1724.2 21.65 91 18_59 9.13428 0.12883 0.45073 0.00645 0.932426 2311.2 17.08 2398.5 28.65 104 18_60 9.12342 0.12784 0.44907 0.00637 0.932426 2315.4 17.14 2391.1 28.33 103 19_61 4.38329 0.06196 0.29607 0.0041 0.932426 1755.1 19.71 1671.8 20.42 95 19_62 3.76753 0.05621 0.28145 0.00421 0.932426 1570 19.76 1598.7 21.17 102 19_63 6.63578 0.09062 0.37772 0.00521 0.932426 2062.3 17.53 2065.6 24.4 100 20_64 4.71118 0.06528 0.31713 0.00441 0.932426 1761.6 18.47 1775.7 21.6 101 20_65 4.00981 0.05716 0.28151 0.00403 0.932426 1684.7 18.79 1599 20.28 95 20_66 2.42163 0.03583 0.21194 0.00304 0.932426 1266.3 21.66 1239.1 16.15 98 20_67 5.07728 0.07216 0.32951 0.00467 0.932426 1828.4 18.71 1836 22.65 100 20_68 5.20415 0.07671 0.33676 0.0048 0.932426 1833.6 20.58 1871.1 23.14 102 20_69 5.03243 0.06929 0.32472 0.00451 0.932426 1839 18.13 1812.7 21.96 99 20_70 3.90291 0.05617 0.27971 0.00407 0.932426 1647.2 18.92 1589.9 20.48 97 20_71 4.33566 0.05711 0.2885 0.00381 0.842469 1783.1 18.21 1634 19.08 92 21_72 8.6567 0.11863 0.42247 0.0057 0.842469 2330.4 18.28 2271.7 25.81 97 21_73 5.6184 0.0821 0.33193 0.00482 0.842469 1996.5 18.85 1847.7 23.32 93 21_74 4.87391 0.07107 0.31309 0.00449 0.842469 1846.7 19.61 1755.9 22.02 95 21_75 5.25407 0.07681 0.33424 0.00478 0.842469 1864.4 19.73 1858.9 23.11 100 21_76 4.33319 0.06451 0.28828 0.00419 0.842469 1783.1 20.1 1632.9 20.99 92 21_77 3.77707 0.05025 0.26281 0.00349 0.842469 1701.1 18.69 1504.2 17.84 88 22_78 4.97386 0.07113 0.31985 0.00448 0.842469 1845 19.51 1789 21.88 97 22_79 3.91269 0.05542 0.28182 0.00397 0.842469 1637 19.25 1600.5 19.97 98 22_80 8.05348 0.11721 0.39291 0.00575 0.842469 2330.5 17.43 2136.3 26.61 92 22_81 4.65989 0.06746 0.28925 0.00416 0.842469 1908.6 18.68 1637.8 20.81 86 22_82 8.27632 0.11547 0.40054 0.00562 0.842469 2344.4 17.25 2171.5 25.87 93 22_83 5.1593 0.06832 0.33128 0.0042 0.842469 1847.1 20.15 1844.6 20.33 100 22_84 2.44631 0.03371 0.20669 0.00279 0.842469 1334.7 20.7 1211.2 14.9 91 23_85 5.97957 0.08352 0.35761 0.00492 0.867508 1974.9 18.74 1970.8 23.35 100 23_86 4.84249 0.06636 0.31745 0.00426 0.867508 1809.7 19.21 1777.3 20.86 98 23_87 10.34017 0.1628 0.47222 0.00703 0.867508 2442.8 20.8 2493.3 30.77 102 23_88 6.99088 0.11365 0.35984 0.00554 0.867508 2239.6 21 1981.4 26.29 88 23_89 5.34923 0.07715 0.33814 0.00478 0.867508 1875.7 18.97 1877.7 23.04 100 23_90 3.33593 0.0502 0.15713 0.00232 0.867508 2391.1 17.98 940.8 12.95 39 24_91 4.31305 0.06105 0.29558 0.00402 0.867508 1729.1 20.19 1669.4 20.01 97 24_92 5.88484 0.08489 0.34792 0.0049 0.867508 1995.5 18.93 1924.7 23.45 96 24_93 6.79177 0.09588 0.37076 0.00518 0.867508 2136.3 17.96 2033 24.38 95 24_94 5.63871 0.07645 0.33251 0.00446 0.867508 2000.2 18.25 1850.6 21.57 93 25_95 4.67498 0.07267 0.29382 0.00421 0.867508 1886.4 22.34 1660.6 21 88 25_96 4.42624 0.0646 0.28138 0.00395 0.867508 1865.9 19.92 1598.3 19.88 86 25_97 4.07122 0.06246 0.16508 0.00247 0.867508 2643.3 18.23 985 13.68 37 25_98 4.3757 0.067 0.296 0.00433 0.867508 1753 20.74 1671.4 21.52 95 25_99 4.30932 0.06857 0.28582 0.00433 0.848618 1790.8 21.56 1620.6 21.71 90 25_100 3.45828 0.05453 0.24541 0.00375 0.848618 1667.9 21.09 1414.8 19.4 85 27_101 5.67376 0.0793 0.34356 0.00478 0.848618 1953.9 18.22 1903.8 22.93 97 27_102 8.62051 0.11976 0.43354 0.00596 0.848618 2279.4 18 2321.7 26.81 102 27_103 7.25382 0.09813 0.39012 0.0051 0.848618 2163.4 19.2 2123.4 23.65 98 27_104 8.00295 0.11573 0.4103 0.0059 0.848618 2246.5 18.12 2216.3 26.98 99 27_105 4.83141 0.06547 0.31115 0.0042 0.848618 1843.1 18.65 1746.4 20.64 95 26_106 4.35342 0.05711 0.28114 0.00364 0.848618 1838.3 19.04 1597.1 18.3 87 20_107 9.81581 0.12823 0.44051 0.00579 0.848618 2474.1 17.04 2352.9 25.93 95 29_108 5.19215 0.06371 0.33483 0.00401 0.859265 1840.7 19.09 1861.8 19.34 101 29_109 5.42401 0.06316 0.33634 0.0039 0.859265 1911.8 18.07 1869 18.83 98 29_110 3.62828 0.04231 0.25748 0.00294 0.859265 1665.5 19.23 1477 15.06 89 29_111 10.07484 0.11714 0.45301 0.00527 0.859265 2470.6 16.85 2408.6 23.39 97 30111 8.13884 0.09646 0.41224 0.00483 0.859265 2267 17.69 2225.2 22.04 98 30_113 4.42703 0.05524 0.30204 0.00358 0.859265 1737.8 20.21 1701.4 17.74 98 30_114 4.9726 0.05955 0.32556 0.00379 0.859265 1813.3 19.18 1816.8 18.42 100 30_115 4.57923 0.05929 0.29786 0.00384 0.859265 1824.2 18.43 1680.7 19.07 92 30_116 5.80161 0.07404 0.35538 0.00429 0.859265 1932.7 20.11 1960.3 20.38 101 32_117 10.65248 0.13706 0.22086 0.0028 0.859265 3705.3 17.05 1286.4 14.79 35 32_118 4.99066 0.06257 0.32626 0.004 0.859265 1815.2 19.03 1820.2 19.42 100 32_119 4.4692 0.0563 0.30852 0.00384 0.859265 1715.6 18.91 1733.4 18.89 101 32_120 5.71782 0.07059 0.35601 0.00427 0.859265 1902.9 18.94 1963.2 20.31 103 32_121 4.14064 0.05401 0.28407 0.00366 0.865975 1726.9 18.9 1611.8 18.37 93 33_122 5.33452 0.06851 0.338 0.00419 0.865975 1871.4 19.43 1877.1 20.17 100 33_123 6.35825 0.08489 0.37458 0.00496 0.865975 2001.8 17.97 2050.9 23.28 102 34_124 5.10262 0.06405 0.32785 0.00404 0.865975 1846.4 18.7 1827.9 19.61 99 34_125 5.04214 0.06345 0.32669 0.00407 0.865975 1831.1 18.4 1822.3 19.78 100 34_126 4.5458 0.05739 0.30267 0.00378 0.865975 1781.5 18.65 1704.6 18.68 96 34_127 5.92707 0.0751 0.35911 0.0045 0.865975 1951.9 18.24 1977.9 21.34 101 36_128 5.32556 0.07458 0.33564 0.0045 0.865975 1881.3 19.98 1865.6 21.74 99 36_129 5.38022 0.0683 0.34231 0.00429 0.865975 1864.1 18.56 1897.8 20.58 102 36_130 4.63009 0.05816 0.3012 0.00375 0.865975 1823.9 18.51 1697.3 18.56 93 36_131 5.33255 0.06808 0.33522 0.00396 0.865975 1885.5 21.1 1863.6 19.14 99 37_132 5.35742 0.06842 0.34066 0.00427 0.865975 1865.2 18.82 1889.8 20.53 101 bh 08 5.009 0.06655 0.31842 0.00407 0.861345 1866.3 19.79 1782 19.89 95
BH12 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
1_1 bh12_1_1 3.91305 0.04949 0.28431 0.00352 1619.5 19.47 1613.1 17.69 100 1_2 bh12_1_2 4.08692 0.05049 0.29252 0.00361 1647.5 18.62 1654.1 18 100 1_3 bh12_2_3 3.91138 0.04847 0.28465 0.00352 1616.7 18.77 1614.7 17.64 100 1_4 bh12_4_4 3.91875 0.04902 0.2835 0.00351 1627.7 19.02 1609 17.63 99 1_5 bh12_4_5 4.0658 0.05035 0.29437 0.00364 1626.4 18.67 1663.3 18.12 102 3_6 bh12_4_6 4.62952 0.06983 0.31694 0.00411 1729.8 24.76 1774.8 20.13 103 3_7 bh12_14_7 3.92547 0.05005 0.2837 0.00354 1629.8 19.54 1610 17.75 99 3_8 bh12_14_8 3.94938 0.05054 0.28768 0.00359 1615.2 19.67 1629.9 17.97 101 3_9 bh12_16_9 4.19434 0.05205 0.30333 0.00376 1628.7 18.62 1707.8 18.6 105 4_10 bh12_17_10 4.14786 0.05216 0.29887 0.00372 1635.6 19 1685.7 18.46 103 4_11 bh12_19_11 4.07668 0.05071 0.29408 0.00365 1633.5 18.63 1661.9 18.19 102 4_12 BH12_14_12 3.90817 0.04965 0.28069 0.00352 1642.5 18.88 1594.8 17.71 97 4_13 BH12_21_13 4.08678 0.05229 0.29278 0.00368 1647.2 19.1 1655.4 18.34 100 5_14 BH12_21_14 4.05519 0.05192 0.29146 0.00366 1641.2 19.12 1648.8 18.28 100 5_15 BH12_24_15 4.14855 0.05289 0.29691 0.00373 1649.1 18.95 1676 18.53 102 5_16 BH12_24_16 4.44904 0.06161 0.31031 0.00398 1696.7 21.55 1742.2 19.56 103 5_17 BH12_30_17 3.94637 0.04997 0.2852 0.00358 1631 18.74 1617.5 17.94 99 6_18 BH12_30_18 4.06954 0.05181 0.28639 0.0036 1680.2 18.79 1623.5 18.02 97 6_19 BH12_37_19 4.17104 0.05326 0.29692 0.00373 1659 18.92 1676 18.55 101 7_20 BH12_37_20 3.9384 0.05007 0.28242 0.00355 1645.4 18.8 1603.5 17.83 97 7_21 BH12_38_21 4.09443 0.05214 0.29389 0.00369 1643.7 18.84 1660.9 18.4 101 7_22 BH12_38_22 4.16881 0.05363 0.29596 0.00373 1664 19.11 1671.3 18.55 100 7_23 BH12_05_23 3.90402 0.04893 0.28491 0.00357 1612.9 18.58 1616.1 17.92 100 8_24 BH12_06_24 3.87055 0.0498 0.27884 0.00352 1637 19.44 1585.5 17.73 97 8_25 BH12_06_25 4.06488 0.05134 0.29363 0.00369 1632 18.89 1659.7 18.37 102 8_26 BH12_16_26 3.87673 0.04822 0.28214 0.00353 1618.1 18.48 1602.1 17.75 99 9_27 bh12_4_27 5.08029 0.06441 0.31925 0.00397 1886.1 18.48 1786 19.38 95 9_28 bh12_4_28 4.15845 0.05299 0.29679 0.0037 1654 19.06 1675.4 18.39 101 10_29 bh12_22_29 3.38015 0.04255 0.24211 0.003 1647.1 18.8 1397.7 15.56 85 10_30 bh12_22_30 3.97943 0.05017 0.28608 0.00355 1640.5 18.8 1621.9 17.82 99 10_31 bh12_22_31 4.28462 0.05458 0.30673 0.00381 1648 19.22 1724.6 18.78 105 10_32 bh12_24_32 4.231 0.05395 0.30126 0.00374 1658.4 19.25 1697.6 18.5 102 11_33 bh12_29_33 4.20592 0.05377 0.29955 0.00372 1657.8 19.34 1689.1 18.45 102 11_34 bh12_31_34 4.02896 0.05156 0.28896 0.0036 1645.1 19.26 1636.3 18 99 11_35 bh12_33_35 4.03132 0.05239 0.28465 0.00355 1673.9 19.76 1614.7 17.83 96 11_36 bh12_33_36 4.06616 0.05236 0.28825 0.00361 1666.4 19.34 1632.8 18.07 98 11_37 bh12_33_37 3.97294 0.05074 0.28245 0.00353 1661.1 19.1 1603.7 17.75 97 12_38 bh12_38 4.17214 0.05293 0.29342 0.00369 1680.9 18.68 1658.6 18.37 99 12_39 bh12_36_39 4.54133 0.06144 0.30252 0.00406 1781.2 18.58 1703.8 20.11 96 12_40 bh12_38_40 3.80166 0.04819 0.26878 0.00337 1671.4 18.64 1534.6 17.14 92 12_41 bh12_38_41 3.86611 0.04914 0.27339 0.00343 1670.8 18.75 1558 17.38 93 12_42 bh12_39_42 4.10691 0.05192 0.29434 0.00368 1645.9 18.7 1663.2 18.35 101 12_43 bh12_39_43 3.76626 0.04776 0.26873 0.00337 1654.2 18.75 1534.3 17.11 93 13_44 bh12_39_44 3.97316 0.05212 0.28416 0.00359 1649.9 19.86 1612.3 18.02 98 13_45 bh12_42_45 4.01658 0.05196 0.29022 0.00366 1630.9 19.43 1642.6 18.26 101 13_46 bh12_44_46 3.99772 0.05073 0.28673 0.00359 1644.7 18.8 1625.2 18 99 13_47 bh12_45_47 4.16316 0.05354 0.29869 0.00375 1644 19.3 1684.8 18.61 102 14_48 bh12_45_48 4.1637 0.0542 0.29675 0.00375 1656.5 19.51 1675.2 18.62 101 14_49 bh12_46_49 4.00887 0.05182 0.29037 0.00367 1626.7 19.54 1643.4 18.34 101 14_50 bh12_46_50 3.93981 0.04988 0.28674 0.00362 1617.7 18.78 1625.2 18.12 100 15_51 bh12_46_51 4.01633 0.05103 0.29139 0.00369 1623.5 18.8 1648.5 18.42 102 15_52 bh12_46_52 3.99245 0.05085 0.29221 0.00371 1607.1 18.91 1652.6 18.5 103 15_53 bh12_49_53 3.97889 0.05025 0.29117 0.0037 1607.4 18.57 1647.4 18.46 102 15_54 bh12_49_54 4.0311 0.05114 0.29447 0.00367 1610.5 19.46 1663.8 18.29 103 15_55 bh12_51_55 4.22937 0.05576 0.30316 0.00391 1646 19.78 1707 19.32 104 16_56 bh12_51_56 3.99516 0.05165 0.29323 0.00376 1601.8 19.25 1657.7 18.77 103 16_57 2_57 3.89975 0.05292 0.28123 0.0038 1634.8 18.97 1597.6 19.12 98 16_58 3_58 3.90453 0.05263 0.28286 0.00382 1626.1 18.58 1605.8 19.21 99 18_59 3_59 3.79012 0.05128 0.27196 0.0036 1644.1 19.77 1550.7 18.22 94 18_60 4_60 3.86264 0.05188 0.2799 0.00375 1625.8 18.91 1590.9 18.87 98 19_61 4_61 3.60295 0.04858 0.26481 0.0036 1599.6 18.48 1514.4 18.35 95 19_62 4_62 3.62103 0.05013 0.2594 0.00361 1646.9 18.43 1486.8 18.47 90 19_63 10_63 3.84883 0.05227 0.27707 0.00373 1638.1 19.15 1576.6 18.82 96 20_64 10_64 3.12485 0.04009 0.22487 0.00288 1639.2 18.65 1307.5 15.14 80 20_65 10_65 3.05236 0.04617 0.22106 0.00293 1627.9 24.73 1287.5 15.49 79 20_66 10_66 3.84246 0.05234 0.27741 0.00377 1632.7 18.87 1578.3 19.01 97 20_67 10_67 3.6801 0.05068 0.2631 0.00351 1651.1 20.03 1505.7 17.92 91 20_68 11_68 3.48928 0.05201 0.20774 0.00315 1983.1 18.48 1216.8 16.83 61 20_69 11_69 4.12973 0.06182 0.2794 0.00382 1752.7 22.77 1588.3 19.22 91 20_70 11_70 3.61305 0.04929 0.2632 0.0036 1616.3 18.7 1506.2 18.37 93 20_71 11_71 3.63454 0.05208 0.25212 0.00345 1706.8 20.83 1449.4 17.75 85 21_72 13_72 3.99094 0.0561 0.28908 0.004 1627 19.61 1637 20.01 101 21_73 15_73 3.4275 0.04863 0.25373 0.00369 1587.5 18.32 1457.7 18.96 92 21_74 15_74 4.01113 0.05609 0.29026 0.00403 1628.4 19.05 1642.8 20.12 101 21_75 16_75 3.73836 0.05176 0.27338 0.0038 1609.2 18.67 1557.9 19.26 97 21_76 17_76 4.0606 0.05601 0.29291 0.004 1634.4 18.89 1656.1 19.96 101 21_77 18_77 4.02413 0.05545 0.29147 0.004 1626.9 18.76 1648.9 19.97 101 22_78 18_78 3.95582 0.05569 0.28673 0.00401 1625.6 19.14 1625.2 20.07 100 22_79 18_79 4.36107 0.06148 0.31508 0.00435 1631.5 19.52 1765.7 21.35 108 22_80 26_80 3.75651 0.05375 0.27062 0.00378 1636.8 19.87 1544 19.2 94 22_81 26_81 3.89394 0.05585 0.27675 0.00379 1661.7 20.68 1575 19.12 95 22_82 27_82 3.76418 0.05684 0.27205 0.00388 1630.8 21.76 1551.2 19.65 95 22_83 27_83 3.97996 0.05779 0.28161 0.00398 1670 20 1599.5 20 96 22_84 30_84 4.40244 0.06284 0.27576 0.00398 1892 17.81 1570 20.11 83 23_85 30_85 4.08378 0.06156 0.29134 0.00418 1654.3 21.34 1648.2 20.85 100 23_86 bh12_1_1 3.91305 0.04949 0.28431 0.00352 1619.5 19.47 1613.1 17.69 100 23_87 bh12_1_2 4.08692 0.05049 0.29252 0.00361 1647.5 18.62 1654.1 18 100 23_88 bh12_2_3 3.91138 0.04847 0.28465 0.00352 1616.7 18.77 1614.7 17.64 100 23_89 bh12_4_4 3.91875 0.04902 0.2835 0.00351 1627.7 19.02 1609 17.63 99 23_90 bh12_4_5 4.0658 0.05035 0.29437 0.00364 1626.4 18.67 1663.3 18.12 102 24_91 bh12_4_6 4.62952 0.06983 0.31694 0.00411 1729.8 24.76 1774.8 20.13 103 24_92 bh12_14_7 3.92547 0.05005 0.2837 0.00354 1629.8 19.54 1610 17.75 99 24_93 bh12_14_8 3.94938 0.05054 0.28768 0.00359 1615.2 19.67 1629.9 17.97 101 24_94 bh12_16_9 4.19434 0.05205 0.30333 0.00376 1628.7 18.62 1707.8 18.6 105 25_95 bh12_17_10 4.14786 0.05216 0.29887 0.00372 1635.6 19 1685.7 18.46 103 25_96 bh12_19_11 4.07668 0.05071 0.29408 0.00365 1633.5 18.63 1661.9 18.19 102 25_97 BH12_14_12 3.90817 0.04965 0.28069 0.00352 1642.5 18.88 1594.8 17.71 97 25_98 BH12_21_13 4.08678 0.05229 0.29278 0.00368 1647.2 19.1 1655.4 18.34 100 25_99 BH12_21_14 4.05519 0.05192 0.29146 0.00366 1641.2 19.12 1648.8 18.28 100 25_100 BH12_24_15 4.14855 0.05289 0.29691 0.00373 1649.1 18.95 1676 18.53 102 27_101 BH12_24_16 4.44904 0.06161 0.31031 0.00398 1696.7 21.55 1742.2 19.56 103 27_102 BH12_30_17 3.94637 0.04997 0.2852 0.00358 1631 18.74 1617.5 17.94 99 27_103 BH12_30_18 4.06954 0.05181 0.28639 0.0036 1680.2 18.79 1623.5 18.02 97 27_104 BH12_37_19 4.17104 0.05326 0.29692 0.00373 1659 18.92 1676 18.55 101 27_105 BH12_37_20 3.9384 0.05007 0.28242 0.00355 1645.4 18.8 1603.5 17.83 97 26_106 BH12_38_21 4.09443 0.05214 0.29389 0.00369 1643.7 18.84 1660.9 18.4 101 20_107 BH12_38_22 4.16881 0.05363 0.29596 0.00373 1664 19.11 1671.3 18.55 100 29_108 BH12_05_23 3.90402 0.04893 0.28491 0.00357 1612.9 18.58 1616.1 17.92 100 29_109 BH12_06_24 3.87055 0.0498 0.27884 0.00352 1637 19.44 1585.5 17.73 97 29_110 BH12_06_25 4.06488 0.05134 0.29363 0.00369 1632 18.89 1659.7 18.37 102 29_111 BH12_16_26 3.87673 0.04822 0.28214 0.00353 1618.1 18.48 1602.1 17.75 99 30111 bh12_4_27 5.08029 0.06441 0.31925 0.00397 1886.1 18.48 1786 19.38 95 30_113 bh12_4_28 4.15845 0.05299 0.29679 0.0037 1654 19.06 1675.4 18.39 101 30_114 bh12_22_29 3.38015 0.04255 0.24211 0.003 1647.1 18.8 1397.7 15.56 85 30_115 bh12_22_30 3.97943 0.05017 0.28608 0.00355 1640.5 18.8 1621.9 17.82 99 30_116 bh12_22_31 4.28462 0.05458 0.30673 0.00381 1648 19.22 1724.6 18.78 105 32_117 bh12_24_32 4.231 0.05395 0.30126 0.00374 1658.4 19.25 1697.6 18.5 102 32_118 bh12_29_33 4.20592 0.05377 0.29955 0.00372 1657.8 19.34 1689.1 18.45 102 32_119 bh12_31_34 4.02896 0.05156 0.28896 0.0036 1645.1 19.26 1636.3 18 99 32_120 bh12_33_35 4.03132 0.05239 0.28465 0.00355 1673.9 19.76 1614.7 17.83 96 32_121 bh12_33_36 4.06616 0.05236 0.28825 0.00361 1666.4 19.34 1632.8 18.07 98 33_122 bh12_33_37 3.97294 0.05074 0.28245 0.00353 1661.1 19.1 1603.7 17.75 97 33_123 bh12_38 4.17214 0.05293 0.29342 0.00369 1680.9 18.68 1658.6 18.37 99 34_124 bh12_36_39 4.54133 0.06144 0.30252 0.00406 1781.2 18.58 1703.8 20.11 96 34_125 bh12_38_40 3.80166 0.04819 0.26878 0.00337 1671.4 18.64 1534.6 17.14 92 34_126 bh12_38_41 3.86611 0.04914 0.27339 0.00343 1670.8 18.75 1558 17.38 93 34_127 bh12_39_42 4.10691 0.05192 0.29434 0.00368 1645.9 18.7 1663.2 18.35 101 36_128 bh12_39_43 3.76626 0.04776 0.26873 0.00337 1654.2 18.75 1534.3 17.11 93 36_129 bh12_39_44 3.97316 0.05212 0.28416 0.00359 1649.9 19.86 1612.3 18.02 98 36_130 bh12_42_45 4.01658 0.05196 0.29022 0.00366 1630.9 19.43 1642.6 18.26 101 36_131 bh12_44_46 3.99772 0.05073 0.28673 0.00359 1644.7 18.8 1625.2 18 99 37_132 bh12_45_47 4.16316 0.05354 0.29869 0.00375 1644 19.3 1684.8 18.61 102 bh 08 bh12_45_48 4.1637 0.0542 0.29675 0.00375 1656.5 19.51 1675.2 18.62 101
BH 15 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
15_1_1 3.84377 0.04194 0.2739 0.00297 0.993787 1655.8 18.75 1560.6 15 94 15_1_2 3.82007 0.04296 0.27841 0.00307 0.980529 1614.1 19.24 1583.4 15.49 98 15_2_3 3.75839 0.04587 0.27191 0.00298 0.897975 1627.9 22.15 1550.5 15.08 95 15_2_4 3.84304 0.04442 0.27118 0.00312 0.99539 1674.2 18.74 1546.8 15.84 92 15_2_5 3.63256 0.03961 0.26459 0.00291 0.991454 1615.5 18.37 1513.3 14.84 94 15_2_6 3.54317 0.04078 0.2594 0.00288 0.964644 1606.1 19.88 1486.8 14.74 93 15_3_7 3.60951 0.03972 0.26026 0.00286 0.998614 1634.6 18.69 1491.2 14.62 91 15_3_8 3.82671 0.04345 0.27644 0.00298 0.949404 1631.3 20.18 1573.4 15.06 96 15_3_9 3.76936 0.04223 0.27495 0.00308 0.99987 1613.2 18.75 1565.9 15.57 97 15_3_10 3.64103 0.04149 0.26599 0.00296 0.976579 1610.5 19.48 1520.4 15.09 94 15_4_11 3.70601 0.04118 0.26737 0.00298 0.996956 1634 18.65 1527.4 15.14 93 15_4_12 3.63195 0.04258 0.26512 0.00298 0.958756 1612.1 20.17 1516 15.19 94 15_4_13 3.58209 0.04027 0.26057 0.00296 0.989641 1618.9 18.39 1492.8 15.12 92 15_4_14 3.47709 0.04352 0.25867 0.00307 0.948242 1577 20.92 1483 15.74 94 15_5_15 3.73345 0.0447 0.26264 0.00312 0.992194 1680.9 19.02 1503.4 15.93 89 15_5_16 3.64999 0.04366 0.26359 0.00302 0.957825 1632.6 20.21 1508.2 15.38 92 15_5_17 3.66962 0.04509 0.25385 0.00316 0.987073 1712.8 18.44 1458.3 16.25 85 15_5_18 3.76224 0.04415 0.27456 0.00315 0.977663 1613.4 19.55 1563.9 15.92 97 15_6_19 3.54172 0.03945 0.25671 0.00287 0.996308 1625.9 18.47 1473 14.74 91 15_6_20 3.71995 0.05179 0.27391 0.00351 0.920429 1596.3 22.81 1560.6 17.74 98 15_6_21 3.77456 0.04241 0.26982 0.00304 0.997246 1651.8 18.47 1539.9 15.44 93 15_6_22 4.27254 0.05475 0.30101 0.00353 0.915157 1678.6 21.79 1696.3 17.48 101 15_7_23 3.80588 0.04365 0.27709 0.00316 0.994345 1617.7 18.82 1576.7 15.98 97 15_7_24 3.83189 0.04557 0.27925 0.00325 0.978643 1616.6 19.58 1587.6 16.36 98 15_8_25 3.87153 0.04574 0.28222 0.00334 0.998286 1615.4 18.59 1602.5 16.81 99 15_8_26 3.87532 0.0478 0.28298 0.00343 0.982693 1612.5 19.44 1606.4 17.25 100 15_9_27 4.0759 0.0489 0.29355 0.00354 0.994865 1638 18.53 1659.2 17.63 101 15_9_28 4.12882 0.04884 0.29816 0.00354 0.996313 1632.9 18.54 1682.2 17.56 103 15_9_29 3.9886 0.05051 0.29076 0.00357 0.969564 1615.4 19.94 1645.3 17.83 102 15_9_30 3.99503 0.04919 0.29002 0.00352 0.98573 1623 19.26 1641.6 17.58 101 15_12_31 3.55078 0.04113 0.25767 0.003 0.994896 1623.1 18.47 1477.9 15.36 91 15_12_32 4.00557 0.04972 0.29148 0.00361 0.997773 1618.3 18.93 1648.9 18.02 102 15_12_33 4.19301 0.05442 0.27817 0.00363 0.994572 1788.8 18.29 1582.1 18.31 88 15_13_34 3.959 0.05099 0.28662 0.0036 0.975206 1627.7 19.78 1624.6 18.06 100 15_14_35 4.04227 0.05088 0.29154 0.00367 0.999894 1635.1 18.59 1649.2 18.31 101 15_14_36 4.04014 0.05218 0.29407 0.00371 0.976822 1617.9 19.7 1661.8 18.47 103 15_15_37 4.19112 0.0546 0.28579 0.00373 0.998161 1738.5 18.34 1620.4 18.68 93 15_15_38 3.98169 0.05168 0.28489 0.00354 0.957351 1649.9 20.32 1615.9 17.75 98 15_15_39 4.11485 0.0518 0.29895 0.00376 0.999111 1621.7 18.55 1686.1 18.65 104 15_15_40 4.15954 0.04957 0.29884 0.00356 0.999626 1642 18.5 1685.6 17.68 103 15_16_41 4.23939 0.05336 0.29759 0.00372 0.993144 1685.3 18.69 1679.3 18.48 100 15_16_42 4.31599 0.05445 0.31117 0.00386 0.983269 1635.7 19.21 1746.5 18.99 107 15_16_43 4.06607 0.05131 0.29028 0.00364 0.993704 1654 18.73 1642.9 18.19 99 15_16_44 4.1355 0.05662 0.29763 0.00391 0.959529 1639 20.58 1679.5 19.41 102 15_17_45 4.65266 0.05939 0.28942 0.00367 0.993403 1904.9 18.3 1638.7 18.34 86 15_17_46 4.05359 0.05154 0.29337 0.0037 0.991931 1628.6 18.94 1658.4 18.42 102 15_17_47 4.1919 0.05277 0.30571 0.00372 0.966623 1614 19.99 1719.6 18.39 107 15_17_48 4.43795 0.05784 0.30357 0.00394 0.995844 1732.7 18.61 1709 19.48 99 15_17_49 4.34446 0.06752 0.3133 0.00414 0.850243 1635 25.79 1756.9 20.3 107 15_18_50 4.25012 0.05815 0.29048 0.00393 0.988844 1733.3 18.91 1643.9 19.62 95 15_18_51 4.49403 0.05657 0.30679 0.00386 0.99953 1736.2 18.34 1724.9 19.04 99 15_18_52 4.22771 0.05696 0.29518 0.00378 0.950474 1694.9 20.66 1667.3 18.82 98 15_18_53 4.37292 0.05696 0.30515 0.00384 0.966094 1695.6 19.92 1716.8 18.97 101 15_20_54 4.04062 0.04969 0.29314 0.00362 0.995835 1624.2 18.5 1657.2 18.02 102 15_22_55 3.9938 0.04823 0.28916 0.00348 0.996575 1627.5 18.73 1637.3 17.41 101 15_22_56 4.04739 0.0512 0.29489 0.00356 0.954322 1615.7 20.52 1665.9 17.7 103 15_23_57 4.19894 0.05085 0.30652 0.00372 0.997854 1612.9 18.49 1723.5 18.38 107 15_23_58 3.90621 0.04922 0.28542 0.0035 0.97319 1611.1 19.82 1618.6 17.54 100 15_25_59 3.8405 0.04596 0.28164 0.00339 0.99423 1604.2 18.52 1599.6 17.03 100 15_25_60 3.6819 0.04526 0.27195 0.0033 0.987148 1591.1 19.28 1550.7 16.75 97 15_25_61 3.82912 0.04599 0.27763 0.0033 0.989653 1625.2 19.05 1579.4 16.64 97 15_25_62 3.61491 0.04498 0.26591 0.0032 0.967149 1598.6 20.01 1520 16.31 95 15_30_63 3.7567 0.04722 0.26847 0.00339 0.995441 1652.5 18.82 1533 17.22 93 15_30_64 3.76088 0.04474 0.27225 0.00324 0.999607 1628.5 18.75 1552.2 16.4 95 15_31_65 3.82426 0.04456 0.27915 0.0033 0.985647 1612.8 18.31 1587.1 16.62 98 15_31_66 3.88143 0.04862 0.28902 0.00358 0.988853 1575.7 19.54 1636.6 17.93 104 15_32_67 4.01714 0.04712 0.29296 0.00349 0.984626 1614.8 18.37 1656.3 17.39 103 15_32_68 3.69593 0.04521 0.27279 0.00336 0.993116 1592.1 18.91 1555 17 98 15_32_69 3.71299 0.04239 0.26578 0.00306 0.991609 1648.8 18.36 1519.3 15.58 92 15_32_70 3.69079 0.04358 0.26707 0.00311 0.986205 1628.7 19.25 1525.9 15.83 94 15_35_71 3.80681 0.04446 0.27222 0.00314 0.987646 1650.3 19.07 1552.1 15.91 94 15_35_72 3.66981 0.04344 0.26502 0.00308 0.981806 1631.8 19.37 1515.5 15.71 93
BH 16 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
1_1 0.10651 0.00104 0.31532 0.00393 4.63076 1740.5 17.85 1754.8 10.11 102 1_2 0.1304 0.00137 0.37124 0.00465 6.67437 2103.3 18.28 2069.2 11.12 97 1_3 0.10077 0.00099 0.30939 0.00386 4.29853 1638.2 18.08 1693.1 9.99 106 1_4 0.10069 0.00098 0.30263 0.00378 4.20167 1636.9 17.9 1674.3 9.91 104 2_1 0.10345 0.00101 0.30288 0.00382 4.32031 1686.9 17.86 1697.2 10.06 101 2_2 0.10039 0.00098 0.32287 0.00405 4.46911 1631.3 18.12 1725.3 10.11 111 2_7 0.10092 0.00099 0.31551 0.00397 4.39015 1641.1 18.03 1710.5 10.07 108 3_8 0.10099 0.00098 0.30762 0.00388 4.2835 1642.4 17.97 1690.2 10.03 105 3_9 0.1014 0.00098 0.31018 0.00392 4.33638 1649.8 17.75 1700.3 10.01 106 3_10 0.10138 0.00099 0.30996 0.0039 4.3324 1649.5 17.96 1699.5 10.07 106 3_11 0.10022 0.00098 0.31213 0.00397 4.31274 1628.1 18.07 1695.8 10.13 108 3_12 0.10148 0.001 0.31952 0.00404 4.47035 1651.4 18.2 1725.5 10.23 108 4_13 0.10334 0.00102 0.32933 0.00421 4.69258 1684.9 18.03 1765.9 10.43 109 4_14 0.1025 0.00101 0.30028 0.00382 4.24337 1669.8 18.08 1682.5 10.25 101 4_15 0.09988 0.00099 0.2965 0.00405 4.08549 1621.8 18.41 1651.4 10.77 103 4_16 0.10526 0.00105 0.30237 0.00382 4.3879 1718.8 18.15 1710.1 10.33 99 5_17 0.10258 0.00101 0.29375 0.00374 4.15428 1671.3 18.13 1665.1 10.25 99 5_18 0.10388 0.00102 0.31756 0.00407 4.54802 1694.5 18.07 1739.8 10.45 105 5_19 0.10361 0.00102 0.31204 0.004 4.45757 1689.8 18.05 1723.1 10.41 104 7_20 0.10416 0.00102 0.31409 0.00402 4.51059 1699.5 18 1732.9 10.43 104 7_21 0.10479 0.00105 0.30974 0.00401 4.47499 1710.6 18.32 1726.3 10.61 102 7_22 0.1057 0.00107 0.31574 0.00408 4.60122 1726.5 18.41 1749.5 10.66 102 8_23 0.10144 0.00114 0.29618 0.00386 4.1422 1650.7 20.76 1662.7 11.12 101 9_24 0.11615 0.00119 0.32885 0.00425 5.26657 1897.8 18.3 1863.5 10.79 97 9_25 0.09892 0.00095 0.30173 0.00387 4.11529 1603.9 17.82 1657.3 9.99 106 10_26 0.10123 0.00097 0.28886 0.0037 4.03188 1646.9 17.7 1640.7 9.95 99 10_27 0.10362 0.001 0.30309 0.00389 4.33029 1690 17.77 1699.1 10.14 101 11_28 0.10163 0.00098 0.30503 0.00391 4.27398 1654.1 17.85 1688.4 10.12 104 11_29 0.10289 0.001 0.31844 0.00409 4.51713 1676.8 17.8 1734.1 10.23 106 12_30 0.09804 0.00097 0.30125 0.00387 4.07215 1587.3 18.36 1648.7 10.14 107 12_31 0.10019 0.00099 0.30106 0.00387 4.15864 1627.7 18.19 1665.9 10.16 104 13_32 0.09986 0.00097 0.3195 0.0041 4.39851 1621.4 18.06 1712.1 10.23 110 14_33 0.10037 0.001 0.32058 0.00412 4.43621 1631 18.35 1719.1 10.35 110 14_34 0.09941 0.00097 0.30064 0.00386 4.12029 1613.1 18.04 1658.3 10.1 105 15_35 0.09831 0.00098 0.30582 0.00393 4.14501 1592.4 18.45 1663.2 10.23 108 15_36 0.10067 0.00099 0.32866 0.00422 4.56117 1636.4 18.08 1742.2 10.33 112 15_37 0.09626 0.00094 0.28552 0.00364 3.78892 1552.9 18.21 1590.4 9.91 104 15_38 0.10599 0.00105 0.31529 0.00403 4.60655 1731.6 18.08 1750.5 10.46 102 15_39 0.10062 0.00099 0.31061 0.00396 4.30811 1635.5 18.15 1694.9 10.23 107 18_40 0.11816 0.0012 0.30671 0.00391 4.99573 1928.5 18.04 1818.6 10.66 89 18_41 0.10334 0.00104 0.31145 0.00397 4.43687 1685 18.38 1719.2 10.41 104 18_42 0.10345 0.00102 0.3138 0.00401 4.47479 1686.9 18.15 1726.3 10.35 104 18_43 0.1011 0.001 0.31193 0.00399 4.34716 1644.4 18.23 1702.4 10.29 106 18_44 0.0992 0.001 0.29184 0.00376 3.99047 1609.1 18.6 1632.3 10.25 103 19_45 0.10342 0.00107 0.31723 0.00398 4.52288 1686.4 19 1735.2 10.52 105 19_46 0.10132 0.00099 0.31294 0.00401 4.37082 1648.5 18.07 1706.8 10.3 106 19_47 0.10258 0.00102 0.30505 0.00391 4.31348 1671.4 18.21 1695.9 10.39 103 19_48 0.10163 0.00105 0.31134 0.00379 4.36202 1654.2 18.95 1705.2 10.14 106 19_49 0.10416 0.00106 0.28669 0.00367 4.11617 1699.5 18.67 1657.5 10.4 96 20_50 0.09947 0.001 0.31103 0.00401 4.26508 1614.3 18.66 1686.6 10.44 108 20_51 0.10539 0.00108 0.31542 0.00404 4.58274 1721.1 18.78 1746.1 10.68 103 20_52 0.10591 0.00116 0.31843 0.00411 4.6492 1730.1 19.91 1758.2 11.06 103 20_53 0.10168 0.00104 0.30092 0.00387 4.2177 1654.9 18.8 1677.5 10.47 102 20_54 0.09991 0.001 0.3078 0.00394 4.23936 1622.5 18.52 1681.7 10.35 107 20_55 0.10273 0.00102 0.29435 0.00376 4.16876 1674.1 18.29 1667.9 10.3 99 20_56 0.10242 0.00101 0.32239 0.00411 4.55168 1668.4 18.13 1740.5 10.35 108 23_57 0.13054 0.00131 0.37251 0.00475 6.70382 2105.3 17.49 2073.1 11.14 97 23_58 0.09948 0.00099 0.30128 0.00385 4.13156 1614.3 18.49 1660.6 10.29 105 23_59 0.10332 0.00107 0.31241 0.00399 4.44991 1684.6 19.01 1721.7 10.63 104 23_60 0.1047 0.00109 0.3139 0.00406 4.53062 1709 18.99 1736.6 10.66 103 23_61 0.10073 0.00102 0.29974 0.004 4.16076 1637.5 18.69 1666.3 10.78 103 24_62 0.10332 0.00102 0.30295 0.004 4.31492 1684.5 18.1 1696.2 10.66 101 24_63 0.10072 0.00099 0.29843 0.00395 4.14372 1637.4 18.23 1663 10.6 103 25_64 0.09863 0.00098 0.28732 0.00383 3.90667 1598.4 18.39 1615.1 10.6 102 27_65 0.10417 0.00103 0.3088 0.00409 4.43465 1699.7 18.1 1718.8 10.74 102 27_66 0.1018 0.00101 0.29848 0.00391 4.18922 1657.2 18.31 1671.9 10.61 102 28_67 0.15501 0.00155 0.41971 0.00555 8.96942 2401.9 16.87 2334.9 11.94 94 28_68 0.09819 0.00103 0.28227 0.00374 3.82103 1590 19.46 1597.2 10.76 101 28_69 0.10439 0.00104 0.3139 0.00417 4.51803 1703.7 18.27 1734.3 10.88 103 28_70 0.10454 0.00113 0.30544 0.00395 4.40256 1706.3 19.78 1712.8 10.98 101 28_71 0.101 0.00101 0.3009 0.00394 4.19046 1642.7 18.46 1672.2 10.65 103 28_72 0.09925 0.001 0.29262 0.00382 4.00433 1610 18.65 1635.1 10.55 103 30_73 0.10429 0.00105 0.30968 0.00413 4.45308 1701.9 18.42 1722.3 10.95 102 30_74 0.10237 0.0011 0.32263 0.00419 4.55396 1667.5 19.81 1740.9 11.1 108 30_75 0.10789 0.00112 0.32817 0.00425 4.88196 1764.1 18.84 1799.1 11.03 104 30_76 0.10135 0.00104 0.31019 0.00405 4.33521 1649.1 18.92 1700.1 10.81 106 30_77 0.10448 0.00106 0.30316 0.00405 4.36764 1705.3 18.58 1706.2 10.98 100 31_78 0.17322 0.00174 0.48028 0.00629 11.47229 2589 16.64 2562.3 12.08 98 31_79 0.10292 0.00105 0.30084 0.00383 4.26941 1677.4 18.73 1687.5 10.48 101 32_80 0.10044 0.00101 0.27624 0.00353 3.82588 1632.3 18.59 1598.2 10.24 96 32_81 0.1028 0.00107 0.31068 0.00398 4.40398 1675.4 19.06 1713.1 10.67 104 32_82 0.1015 0.00104 0.30835 0.00392 4.31532 1651.7 18.78 1696.3 10.47 105 33_83 0.10319 0.00105 0.31921 0.00412 4.54146 1682.2 18.69 1738.6 10.69 106 33_84 0.10518 0.00107 0.30847 0.00399 4.47341 1717.5 18.59 1726.1 10.66 101 33_85 0.10002 0.00101 0.29069 0.00369 4.00841 1624.4 18.61 1635.9 10.27 101 33_86 0.10232 0.00103 0.30681 0.00379 4.32784 1666.6 18.59 1698.7 10.19 104 34_87 0.09634 0.00101 0.24679 0.00312 3.27778 1554.3 19.53 1475.8 9.97 91 34_88 0.10209 0.00101 0.3303 0.00424 4.64882 1662.4 18.19 1758.1 10.55 111 35_89 0.14733 0.00147 0.43205 0.00557 8.77555 2315.1 17.01 2315 11.6 100 35_90 0.11011 0.00113 0.34408 0.00421 5.22309 1801.2 18.64 1856.4 10.51 106 35_91 0.10508 0.00105 0.32852 0.00416 4.75913 1715.7 18.3 1777.7 10.53 107 35_92 0.10387 0.00104 0.31671 0.00395 4.53553 1694.4 18.31 1737.5 10.3 105 36_93 0.10541 0.00109 0.32498 0.00407 4.72298 1721.5 18.86 1771.3 10.6 105 36_94 0.1014 0.00104 0.30214 0.00376 4.22398 1649.9 18.82 1678.7 10.25 103 37_95 0.10373 0.00114 0.30559 0.004 4.37031 1691.9 20.06 1706.7 11.11 102 37_96 0.10314 0.00105 0.30359 0.0039 4.31702 1681.5 18.69 1696.6 10.52 102 38_97 0.11779 0.00122 0.33038 0.0039 5.36462 1922.9 18.39 1879.2 10.25 96 38_98 0.10105 0.00103 0.29288 0.0035 4.07952 1643.5 18.77 1650.2 9.79 101 38_99 0.10281 0.00105 0.31355 0.00413 4.44485 1675.5 18.76 1720.7 10.88 105 38_100 0.10369 0.00104 0.31438 0.00403 4.49202 1691.1 18.43 1729.5 10.52 104 39_101 0.10277 0.00104 0.31818 0.00399 4.5066 1674.8 18.51 1732.2 10.38 106 39_102 0.10432 0.00111 0.33456 0.00414 4.81007 1702.3 19.4 1786.7 10.61 109 40_103 0.10184 0.00104 0.31266 0.00385 4.38854 1657.9 18.78 1710.2 10.22 106 40_104 0.10424 0.00104 0.31962 0.00396 4.59124 1700.9 18.28 1747.7 10.27 105 41_105 0.10464 0.00105 0.33651 0.00424 4.85359 1708 18.42 1794.2 10.56 109 41_106 0.10381 0.00104 0.31989 0.00419 4.57742 1693.3 18.43 1745.2 10.79 106 42_107 0.10219 0.00103 0.29635 0.00388 4.17475 1664.2 18.48 1669.1 10.65 101 43_108 0.10267 0.00104 0.29901 0.00378 4.23129 1673 18.59 1680.1 10.33 101 44_109 0.10146 0.00102 0.2961 0.00388 4.14142 1651 18.54 1662.5 10.6 101 44_110 0.10336 0.00103 0.3158 0.00423 4.50031 1685.3 18.34 1731 10.95 105 46_111 0.10261 0.00104 0.30672 0.00392 4.33822 1671.8 18.55 1700.7 10.46 103 49_112 0.10266 0.00102 0.31066 0.004 4.39528 1672.8 18.23 1711.5 10.45 104 52_113 0.10378 0.00105 0.30124 0.00384 4.30852 1692.7 18.53 1695 10.44 100 53_114 0.10371 0.00104 0.30045 0.0039 4.2947 1691.6 18.4 1692.3 10.56 100 54_115 0.10333 0.00103 0.31673 0.00402 4.51056 1684.9 18.31 1732.9 10.43 105 54_116 0.0973 0.00111 0.30021 0.00391 4.02601 1573 21.16 1639.5 11.08 108 56_117 0.09972 0.00099 0.33089 0.00426 4.54833 1618.9 18.31 1739.9 10.5 114 56_118 0.1421 0.00143 0.43704 0.00545 8.56062 2252.9 17.29 2292.4 11.27 104 56_119 0.10191 0.00101 0.34345 0.00446 4.82432 1659.2 18.26 1789.1 10.72 115 56_120 0.14956 0.00149 0.45718 0.00582 9.42493 2340.8 17.01 2380.3 11.54 104 59_121 0.1022 0.00105 0.33062 0.0042 4.65761 1664.4 18.89 1759.7 10.65 111 60_122 0.10182 0.00101 0.32354 0.00415 4.54133 1657.6 18.22 1738.6 10.48 109 64_123 0.1332 0.00137 0.35467 0.00442 6.51257 2140.5 17.84 2047.6 10.99 91 64_124 0.10187 0.00101 0.30051 0.00385 4.22018 1658.4 18.25 1678 10.34 102 65_125 0.09979 0.00098 0.30059 0.004 4.13456 1620.1 18.22 1661.2 10.58 105 16_1_126 0.10383 0.00104 0.29295 0.00393 4.19308 1693.7 18.35 1672.7 10.86 98 16_1_127 0.14332 0.00146 0.30499 0.00398 6.03461 2267.7 17.41 1980.9 11.29 76 16_2_128 0.1057 0.00106 0.30065 0.00411 4.37875 1726.6 18.32 1708.3 11.12 98 16_2_129 0.10093 0.001 0.28893 0.00397 4.0182 1641.3 18.31 1637.9 10.96 100 16_2_130 0.1 0.00101 0.28334 0.00358 3.90984 1624.2 18.76 1615.7 10.16 99 16_3_131 0.10444 0.00103 0.30864 0.00429 4.44109 1704.5 18.07 1720 11.26 102 16_3_132 0.10315 0.00101 0.30765 0.00429 4.37184 1681.5 18.03 1707 11.26 103 16_3_133 0.10332 0.00104 0.30244 0.00425 4.30578 1684.5 18.42 1694.5 11.4 101
BH17 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy 17_2_1 3.43103 0.04891 0.25938 0.00368 0.995264 1545 19.67 1486.7 18.86 96 17_2_2 3.86489 0.05509 0.28541 0.00404 0.993062 1589 19.69 1618.6 20.27 102 17_2_3 3.93053 0.056 0.28998 0.00416 0.993143 1591.2 19.11 1641.4 20.79 103 17_3_4 3.73345 0.05637 0.2759 0.00413 0.991427 1588.6 20.23 1570.7 20.86 99 17_3_5 3.77043 0.05445 0.28234 0.00407 0.998194 1563.7 19.72 1603.1 20.44 103 17_3_6 3.68441 0.05623 0.27693 0.00416 0.98429 1557 20.77 1575.9 20.98 101 17_4_7 3.43381 0.05106 0.25828 0.00386 0.994966 1555.9 19.61 1481 19.76 95 17_4_8 3.71687 0.05443 0.27797 0.00407 0.999852 1566.9 19.74 1581.1 20.51 101 17_5_9 3.82248 0.05618 0.28592 0.00422 0.995792 1566.8 19.42 1621.1 21.16 103 17_5_10 3.5255 0.05367 0.26845 0.00409 0.999197 1533.6 20.04 1532.9 20.79 100 17_5_11 3.40673 0.05199 0.26186 0.004 0.999059 1516.1 20.19 1499.4 20.42 99 17_5_12 3.83618 0.05621 0.28903 0.00429 0.987189 1554.1 19.11 1636.7 21.46 105 17_6_13 3.67307 0.05001 0.27438 0.00369 0.987748 1569.6 20.07 1563 18.67 100 17_9_14 3.60196 0.04909 0.26577 0.00359 0.991138 1592.9 19.98 1519.3 18.26 95 17_9_15 3.54224 0.04728 0.26585 0.00356 0.99675 1560.8 19.32 1519.7 18.14 97 17_10_16 3.92177 0.05395 0.28159 0.00377 0.973228 1643.7 20.51 1599.3 18.97 97 17_10_17 3.53718 0.04965 0.26135 0.00363 0.989514 1590.2 20.07 1496.8 18.56 94 17_11_18 3.7129 0.05193 0.27707 0.00388 0.998764 1571.9 19.5 1576.6 19.59 100 17_12_19 3.78961 0.05485 0.28214 0.00404 0.989315 1576.2 20.21 1602.1 20.3 102 17_12_20 3.8418 0.05235 0.28728 0.00394 0.993553 1567.5 19.15 1627.9 19.72 104 17_13_21 3.5639 0.05153 0.26752 0.00388 0.996917 1560.9 19.36 1528.2 19.76 98 17_15_22 3.83368 0.0559 0.28223 0.00409 0.993858 1596.9 19.82 1602.6 20.56 100 17_17_23 3.80718 0.05504 0.28557 0.0041 0.993107 1561.8 19.92 1619.4 20.58 104 17_17_24 3.88702 0.05572 0.28775 0.00414 0.996344 1585.8 19.41 1630.3 20.74 103 17_17_25 3.97809 0.0566 0.29738 0.00426 0.993217 1567.6 19.21 1678.3 21.16 107 17_18_26 3.92342 0.05589 0.29172 0.00419 0.991794 1577.3 19.09 1650.1 20.9 105 17_20_27 3.77879 0.05686 0.2795 0.0041 0.974873 1587.2 20.81 1588.9 20.65 100 17_20_28 3.9908 0.06073 0.29005 0.0044 0.996865 1620.2 19.82 1641.8 21.99 101 17_20_29 3.85723 0.05658 0.28178 0.00411 0.994361 1610.5 19.63 1600.3 20.67 99 17_20_30 4.11296 0.05953 0.30302 0.00441 0.994521 1594.7 19.06 1706.3 21.81 107 17_21_31 4.00071 0.05971 0.29217 0.00428 0.981518 1611.1 20.39 1652.4 21.35 103 17_21_32 3.72476 0.05651 0.27789 0.00414 0.981975 1571.3 20.54 1580.7 20.9 101 17_22_33 3.69812 0.05595 0.27517 0.00417 0.998353 1576.1 19.64 1567 21.07 99 17_22_34 3.73806 0.0549 0.27701 0.00406 0.99794 1583.9 19.49 1576.3 20.51 100 17_23_35 3.74109 0.05525 0.27729 0.00408 0.996304 1583.6 19.66 1577.7 20.58 100 17_23_36 3.75304 0.05428 0.28071 0.00402 0.990174 1566.5 19.78 1595 20.26 102 17_23_37 3.5414 0.0524 0.26417 0.00393 0.994597 1571.6 19.37 1511.2 20.02 96 17_26_38 3.81955 0.05659 0.27985 0.0041 0.988851 1605.2 20.07 1590.6 20.65 99 17_26_39 3.84868 0.05859 0.28638 0.00431 0.988605 1576.4 20.43 1623.4 21.59 103 17_28_40 3.8714 0.05476 0.28549 0.00412 0.980142 1593.3 18.34 1619 20.68 102 17_28_41 3.94767 0.05875 0.28671 0.00422 0.989014 1621.6 19.84 1625.1 21.13 100 17_30_42 3.87677 0.05739 0.2862 0.00423 0.9984 1591.1 19.38 1622.5 21.2 102 17_30_43 3.72721 0.05481 0.27582 0.00406 0.999023 1586.7 19.16 1570.3 20.53 99 17_31_44 3.81947 0.05848 0.27648 0.00414 0.977985 1627.9 20.45 1573.6 20.92 97 17_31_45 3.6635 0.05698 0.27525 0.00431 0.993291 1558.1 19.47 1567.4 21.81 101 17_31_46 3.45211 0.05277 0.2541 0.00354 0.911373 1596.7 23.58 1459.6 18.19 91 17_31_47 3.39103 0.05232 0.25824 0.00397 0.996394 1533 19.99 1480.8 20.33 97 17_34_48 4.04925 0.06035 0.29683 0.00445 0.994147 1604.5 18.88 1675.6 22.12 104 17_34_49 3.86195 0.05743 0.28686 0.00427 0.99902 1579.8 19.28 1625.8 21.37 103 17_34_50 4.05483 0.06101 0.30092 0.0045 0.993878 1581.5 19.7 1695.8 22.28 107 17_35_51 3.92311 0.05807 0.28831 0.00429 0.994772 1599.8 18.9 1633.1 21.49 102 17_35_52 3.87864 0.0578 0.28653 0.00427 0.999978 1590.1 19.19 1624.2 21.4 102 17_35_53 3.73263 0.05618 0.27436 0.00409 0.990457 1599.5 19.72 1562.9 20.68 98 17_35_54 3.67681 0.05851 0.27687 0.00437 0.991851 1554.1 20.28 1575.6 22.04 101
BH 19 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
19_10_25 3.74835 0.06911 0.27243 0.00377 0.75056 1621 32.85 1553.1 19.11 96 19_10_26 1.9016 0.02061 0.13277 0.00141 0.979852 1695 19.23 803.6 8 47 19_11_27 1.49286 0.01686 0.10732 0.00112 0.924057 1641 21.01 657.2 6.51 40 19_11_28 3.59039 0.06538 0.25826 0.00351 0.746357 1640.5 32.51 1481 18 90 19_11_29 2.81333 0.03256 0.20281 0.00234 0.996926 1636 18.83 1190.4 12.55 73 19_11_30 2.31247 0.03222 0.16562 0.00232 0.994659 1648.3 19.82 987.9 12.86 60 19_12_31 2.62623 0.02849 0.19333 0.00206 0.982219 1597.3 19.25 1139.4 11.14 71 19_12_32 3.96326 0.05059 0.27101 0.00343 0.991509 1733.3 19.1 1545.9 17.39 89 19_12_33 1.1103 0.0131 0.08135 0.00094 0.979353 1607.5 19.57 504.2 5.59 31 19_13_34 4.05737 0.07025 0.29309 0.00412 0.811885 1631.6 29.39 1657 20.52 102 19_14_35 3.37883 0.04366 0.24859 0.00322 0.997574 1597.1 19.1 1431.2 16.61 90 19_14_36 3.8013 0.05096 0.28446 0.00388 0.982849 1565.5 18.96 1613.8 19.47 103 19_14_37 2.31677 0.02571 0.1677 0.0018 0.967209 1628.5 19.68 999.4 9.93 61 19_15 2.74675 0.03714 0.20008 0.00273 0.990978 1615.7 19.11 1175.7 14.64 73 19_16_39 3.96297 0.05294 0.28648 0.00369 0.964204 1629.3 20.74 1623.9 18.49 100 19_16_40 3.75519 0.05955 0.27034 0.00357 0.832737 1636.2 27.06 1542.5 18.12 94 19_16_41 1.58294 0.02195 0.11201 0.00158 0.983037 1667.5 18.64 684.4 9.17 41 19_16_42 3.83672 0.0702 0.27195 0.00405 0.813934 1665 30.56 1550.7 20.52 93 19_16_43 4.07968 0.12594 0.28965 0.00497 0.555834 1663 57.92 1639.8 24.87 99 19_17_44 3.1747 0.04163 0.23119 0.00297 0.979679 1616.4 19.8 1340.8 15.56 83 19_17_45 0.93514 0.01395 0.06616 0.00095 0.962566 1671.3 21.12 413 5.75 25 19_17_46 3.85712 0.05054 0.28282 0.00362 0.976847 1603.4 20.05 1605.5 18.19 100 19_17_47 3.80831 0.06165 0.28096 0.00377 0.828888 1591.9 27.64 1596.2 18.96 100 19_17_48 2.9614 0.1008 0.21292 0.00414 0.571242 1641.6 63.99 1244.4 22.01 76 19_18_49 2.98359 0.04177 0.21907 0.00308 0.995767 1600.9 19.34 1277 16.27 80 19_18_50 3.9907 0.05451 0.29131 0.00395 0.992692 1612.2 19.45 1648.1 19.74 102 19_18_51 3.97637 0.05691 0.29179 0.00424 0.984932 1602.8 18.75 1650.5 21.17 103 19_18_52 3.93153 0.07892 0.28333 0.00418 0.734951 1636.3 35.16 1608.1 21.02 98 19_18_53 3.47684 0.05876 0.25024 0.00334 0.789755 1640.6 29.87 1439.7 17.25 88 19_18_54 0.8919 0.00921 0.06166 0.00061 0.958038 1714.9 19.96 385.7 3.71 22 19_19_55 3.49574 0.07184 0.25393 0.00381 0.730102 1624 37.12 1458.7 19.57 90 19_19_56 3.34331 0.03694 0.22307 0.00246 0.998099 1779.5 18.81 1298.1 12.96 73 19_2_1 3.82181 0.06045 0.28324 0.00445 0.993295 1584.4 20.47 1607.7 22.36 101 19_2_2 3.18744 0.04562 0.23131 0.00333 0.994176 1623.6 18.78 1341.4 17.44 83 19_3_3 3.66161 0.05344 0.26859 0.004 0.979996 1603.3 18.37 1533.6 20.34 96 19_3_4 3.84788 0.05851 0.27493 0.00414 0.990307 1652.1 20.15 1565.8 20.92 95 19_3_5 3.84433 0.05657 0.2817 0.00424 0.977657 1605.1 18.37 1599.9 21.33 100 19_4_6 1.07909 0.01585 0.06721 0.00101 0.977427 1902.4 17.84 419.3 6.09 22 19_4_7 3.82444 0.05812 0.26355 0.004 0.99871 1718.8 19.59 1508 20.39 88 19_4_8 3.89975 0.06834 0.28453 0.00449 0.900492 1613.1 26.25 1614.1 22.52 100 19_5_10 4.02182 0.06153 0.29522 0.00445 0.985258 1601.8 20.26 1667.6 22.14 104 19_5_11 4.23776 0.06394 0.31002 0.00465 0.994093 1608.1 19.69 1740.8 22.9 108 19_5_12 1.2128 0.01818 0.08776 0.00134 0.98174 1628.4 18.56 542.3 7.94 33 19_5_9 3.17225 0.05323 0.22936 0.00388 0.991916 1630.8 20.18 1331.2 20.33 82 19_6_13 1.1797 0.01776 0.09125 0.00138 0.995463 1503.4 19.6 562.9 8.16 37 19_6_14 4.00109 0.06285 0.28537 0.00432 0.963715 1655.3 21.52 1618.3 21.69 98 19_6_15 4.11184 0.06194 0.30061 0.00459 0.986565 1609.1 18.95 1694.3 22.77 105 19_7_16 3.72605 0.05521 0.26366 0.00399 0.97913 1669.7 18.33 1508.5 20.35 90 19_7_17 3.6943 0.05798 0.27241 0.00424 0.991738 1593.3 20.5 1553 21.47 97 19_7_18 1.37936 0.02046 0.09472 0.00143 0.982502 1725 18.4 583.4 8.41 34 19_7_19 1.80872 0.02683 0.12999 0.00196 0.983792 1641.1 18.49 787.8 11.2 48 19_8_20 3.94218 0.05971 0.2841 0.00432 0.996089 1636 19.38 1612 21.68 99 19_8_21 1.9176 0.02822 0.13488 0.00201 0.98753 1681.1 18.62 815.6 11.41 49 19_8_22 3.3637 0.05108 0.24844 0.00384 0.98248 1590.9 18.8 1430.4 19.84 90 19_8_23 4.21797 0.09135 0.25386 0.0046 0.836678 1963.9 33.2 1458.4 23.66 74 19_9_24 2.46582 0.03675 0.17799 0.00269 0.986142 1633.1 18.72 1056 14.72 65
BH 22 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
22_1_1 4.20216 0.06941 0.26113 0.00382 0.88563982 1906.9 25.41 1495.6 19.54 78 22_1_2 3.63795 0.05115 0.26648 0.00372 0.99286319 1606 19.6 1522.9 18.96 95 22_2_3 3.59537 0.05145 0.26599 0.00372 0.97731787 1587.4 20.51 1520.4 18.93 96 22_2_4 3.57006 0.05294 0.26585 0.00378 0.95884126 1575.2 21.57 1519.7 19.27 96 22_3_5 3.55692 0.05275 0.26542 0.00389 0.98825175 1571.6 20.03 1517.5 19.83 97 22_3_6 3.69462 0.05044 0.2699 0.00363 0.9851411 1610.9 19.84 1540.3 18.43 96 22_4_7 3.76045 0.06188 0.26333 0.00387 0.8931001 1689.5 25.39 1506.8 19.73 89 22_4_8 3.56946 0.05129 0.26555 0.00378 0.99063876 1576.8 19.92 1518.2 19.25 96 22_6_9 3.79433 0.05771 0.27067 0.0037 0.89876391 1655.5 24.37 1544.2 18.78 93 22_6_10 3.62213 0.05143 0.26727 0.00378 0.99606825 1592.2 19.59 1526.9 19.24 96 22_8_11 3.70044 0.05391 0.27534 0.00395 0.98471788 1576.6 20.29 1567.9 19.96 99 22_8_12 3.62184 0.05095 0.27048 0.0038 0.99869646 1569.8 19.52 1543.2 19.29 98 22_10_13 3.80105 0.05428 0.28078 0.00398 0.99261457 1590.2 19.54 1595.3 20.06 100 22_10_14 3.8416 0.05756 0.28163 0.00407 0.96451026 1604.4 21.2 1599.6 20.46 100 22_11_15 3.80237 0.05685 0.2804 0.00405 0.96605292 1593.4 21.13 1593.4 20.37 100 22_11_16 3.78955 0.05549 0.27972 0.00403 0.98390789 1591.6 20.17 1590 20.3 100 22_12_17 3.73617 0.05682 0.26788 0.00391 0.95975828 1645.7 21.47 1530 19.86 93 22_12_18 3.62012 0.0508 0.26797 0.00369 0.98129468 1586.2 20.2 1530.5 18.75 96 22_12_19 3.70007 0.05283 0.27502 0.00391 0.9957305 1578.7 19.44 1566.2 19.79 99 22_12_20 3.69775 0.05194 0.27239 0.00377 0.98533927 1595.5 19.82 1552.9 19.13 97 22_13_21 3.57032 0.05382 0.26363 0.00378 0.95117498 1591.1 21.84 1508.4 19.3 95 22_13_22 3.76461 0.05574 0.27722 0.00403 0.98182371 1595.9 20.23 1577.4 20.33 99 22_13_23 3.89119 0.05876 0.27424 0.00398 0.96106536 1677.5 21.11 1562.3 20.12 93 22_13_24 3.63849 0.05152 0.26821 0.00375 0.98741935 1594.2 19.85 1531.7 19.05 96 22_14_25 3.66793 0.05882 0.27202 0.00403 0.92384737 1582.9 23.64 1551.1 20.43 98 22_14_26 3.72152 0.05207 0.27374 0.0038 0.99215177 1598.2 19.49 1559.8 19.21 98 22_15_27 3.21237 0.04586 0.22899 0.00326 0.99722371 1656.6 19.05 1329.2 17.09 80 22_15_28 3.82248 0.05859 0.2818 0.00422 0.9769969 1594 20.54 1600.4 21.24 100 22_15_29 3.79948 0.05629 0.27818 0.00403 0.97784959 1606.9 20.17 1582.2 20.34 98 22_16_30 3.17377 0.04644 0.23002 0.00331 0.98343494 1625.8 19.88 1334.6 17.33 82 22_16_31 3.75394 0.05378 0.27596 0.00389 0.98394312 1599.5 19.78 1571 19.66 98 22_16_32 3.75621 0.0566 0.27529 0.00404 0.97392242 1605.1 20.45 1567.6 20.41 98 22_16_34 3.74719 0.05446 0.27588 0.00396 0.98764995 1596.5 19.62 1570.6 20.01 98 22_18_35 3.67811 0.0602 0.25232 0.00348 0.84266662 1727.8 27.05 1450.4 17.92 84 22_18_36 3.67344 0.05249 0.27145 0.00384 0.99000584 1589.6 19.36 1548.2 19.49 97 22_20_37 3.75671 0.05576 0.27258 0.0039 0.96395226 1623.8 20.77 1553.9 19.75 96 22_20_38 3.78995 0.05573 0.2766 0.004 0.98344993 1613 19.67 1574.2 20.21 98 22_20_39 3.4039 0.04887 0.24815 0.00353 0.99082026 1615 19.17 1428.9 18.24 88 22_20_40 3.80377 0.05595 0.27488 0.00397 0.98188703 1631.3 19.7 1565.5 20.07 96 22_21_41 3.73183 0.0544 0.27257 0.00394 0.99161051 1611.2 19.29 1553.8 19.94 96 22_21_42 3.18544 0.04976 0.22868 0.00349 0.97698141 1643.3 20.41 1327.6 18.29 81 22_22_43 3.94912 0.05855 0.28928 0.00422 0.98393741 1605.8 19.92 1637.9 21.08 102 22_22_44 3.75674 0.0552 0.27503 0.004 0.98981033 1607 19.67 1566.3 20.21 97 22_25_45 3.75539 0.05505 0.27631 0.00398 0.98261681 1597.5 19.9 1572.7 20.1 98 22_25_46 3.72377 0.06186 0.27297 0.00404 0.89092137 1604.4 25.46 1555.9 20.48 97 22_27_47 3.75771 0.05967 0.27515 0.00408 0.9338086 1606.4 22.93 1566.9 20.6 98 22_27_48 3.72959 0.0554 0.27625 0.00393 0.95772669 1585 21.46 1572.5 19.83 99 22_27_49 3.8299 0.05478 0.28158 0.00403 0.99938161 1598.8 18.94 1599.3 20.29 100 22_27_50 3.87653 0.05709 0.28282 0.00413 0.99156923 1613.2 19.62 1605.5 20.73 100 22_31_51 3.75013 0.05477 0.27425 0.00399 0.9961617 1608.7 19.27 1562.4 20.21 97 22_31_52 3.75785 0.05344 0.27553 0.00389 0.99278156 1604 19.52 1568.8 19.66 98 22_31_53 3.70073 0.05434 0.27319 0.00392 0.97721255 1591.3 20.46 1557 19.86 98 22_31_54 3.70489 0.05374 0.27111 0.00386 0.98156581 1607.6 20.06 1546.5 19.59 96 22_1_1 4.20216 0.06941 0.26113 0.00382 0.88563982 1906.9 25.41 1495.6 19.54 78 22_1_2 3.63795 0.05115 0.26648 0.00372 0.99286319 1606 19.6 1522.9 18.96 95 22_2_3 3.59537 0.05145 0.26599 0.00372 0.97731787 1587.4 20.51 1520.4 18.93 96 22_2_4 3.57006 0.05294 0.26585 0.00378 0.95884126 1575.2 21.57 1519.7 19.27 96 22_3_5 3.55692 0.05275 0.26542 0.00389 0.98825175 1571.6 20.03 1517.5 19.83 97 22_3_6 3.69462 0.05044 0.2699 0.00363 0.9851411 1610.9 19.84 1540.3 18.43 96 22_4_7 3.76045 0.06188 0.26333 0.00387 0.8931001 1689.5 25.39 1506.8 19.73 89 22_4_8 3.56946 0.05129 0.26555 0.00378 0.99063876 1576.8 19.92 1518.2 19.25 96 22_6_9 3.79433 0.05771 0.27067 0.0037 0.89876391 1655.5 24.37 1544.2 18.78 93 22_6_10 3.62213 0.05143 0.26727 0.00378 0.99606825 1592.2 19.59 1526.9 19.24 96 22_8_11 3.70044 0.05391 0.27534 0.00395 0.98471788 1576.6 20.29 1567.9 19.96 99 22_8_12 3.62184 0.05095 0.27048 0.0038 0.99869646 1569.8 19.52 1543.2 19.29 98 22_10_13 3.80105 0.05428 0.28078 0.00398 0.99261457 1590.2 19.54 1595.3 20.06 100 22_10_14 3.8416 0.05756 0.28163 0.00407 0.96451026 1604.4 21.2 1599.6 20.46 100 22_11_15 3.80237 0.05685 0.2804 0.00405 0.96605292 1593.4 21.13 1593.4 20.37 100 22_11_16 3.78955 0.05549 0.27972 0.00403 0.98390789 1591.6 20.17 1590 20.3 100 22_12_17 3.73617 0.05682 0.26788 0.00391 0.95975828 1645.7 21.47 1530 19.86 93 22_12_18 3.62012 0.0508 0.26797 0.00369 0.98129468 1586.2 20.2 1530.5 18.75 96 22_12_19 3.70007 0.05283 0.27502 0.00391 0.9957305 1578.7 19.44 1566.2 19.79 99 22_12_20 3.69775 0.05194 0.27239 0.00377 0.98533927 1595.5 19.82 1552.9 19.13 97 22_13_21 3.57032 0.05382 0.26363 0.00378 0.95117498 1591.1 21.84 1508.4 19.3 95 22_13_22 3.76461 0.05574 0.27722 0.00403 0.98182371 1595.9 20.23 1577.4 20.33 99 22_13_23 3.89119 0.05876 0.27424 0.00398 0.96106536 1677.5 21.11 1562.3 20.12 93 22_13_24 3.63849 0.05152 0.26821 0.00375 0.98741935 1594.2 19.85 1531.7 19.05 96 22_14_25 3.66793 0.05882 0.27202 0.00403 0.92384737 1582.9 23.64 1551.1 20.43 98 22_14_26 3.72152 0.05207 0.27374 0.0038 0.99215177 1598.2 19.49 1559.8 19.21 98
BH22 Spot No. Pb207/U235 σ1 Error Pb206/U238 σ1 Error Rho Pb207/Pb206 σ1 Error Pb206/U238 σ1 Error Concordancy
1_1 3.69773 0.04432 0.26887 0.00319 0.989883 1621.1 19.2 1535 16.21 95 1_2 8.59679 0.11802 0.41845 0.00641 0.8962 2338.9 17.78 2253.5 29.12 96 1_3 4.57619 0.05324 0.26518 0.00309 0.998427 2030.7 17.95 1516.3 15.74 75 1_6 5.17822 0.06453 0.3 0.00375 0.996945 2031.7 17.7 1691.3 18.58 83 I05_06 8.02951 0.08826 0.39814 0.00436 0.996267 2302.1 17.57 2160.5 20.1 94 I05_07 9.41219 0.12298 0.44043 0.00584 0.985389 2403.8 17.02 2352.5 26.12 98 I05_08 8.85314 0.11775 0.39577 0.00524 0.995462 2481.8 17.89 2149.5 24.18 87 I05_09 8.99692 0.10076 0.42124 0.0047 0.996263 2401.6 17.44 2266.1 21.33 94 I05_10 4.19749 0.04745 0.27657 0.00313 0.998866 1802.4 18.33 1574.1 15.82 87 I05_11 5.23529 0.06561 0.29636 0.00374 0.993064 2075 17.69 1673.3 18.62 81 I05_12 4.36189 0.05781 0.27807 0.00363 0.984973 1863 19.19 1581.6 18.32 85 I05_13 4.01282 0.04864 0.29447 0.00357 0.999808 1604.3 18.95 1663.8 17.76 104 I05_14 4.75657 0.06094 0.29364 0.00381 0.987413 1920.6 17.9 1659.7 18.99 86 I05_15 3.39271 0.04465 0.21433 0.00285 0.989721 1878.9 18.2 1251.9 15.12 67 I05_16 4.06941 0.04823 0.29886 0.00358 0.989397 1603.2 18.43 1685.6 17.78 105 I05_17 4.5905 0.05282 0.28756 0.00328 0.991304 1893.6 18.53 1629.3 16.42 86 I05_18 11.02588 0.13363 0.46058 0.00559 0.998583 2594.6 16.89 2442.1 24.68 94 I05_7_19 4.1678 0.05097 0.29956 0.0036 0.982677 1640.2 19.3 1689.1 17.85 103 I05_8_20 4.08778 0.04927 0.29832 0.00358 0.995648 1611.8 18.83 1683 17.78 104 I05_8_21 4.04637 0.04993 0.29266 0.00359 0.994112 1628.3 18.81 1654.8 17.89 102 I05_8_22 4.06079 0.0457 0.27996 0.00314 0.996616 1718 18.53 1591.2 15.83 93 I05_9_23 9.81765 0.12653 0.43879 0.00567 0.997378 2478.1 17.04 2345.2 25.4 95 I05_9_24 9.83526 0.11633 0.4343 0.00512 0.996722 2498.6 17.1 2325.1 23 93 I05_9_25 4.10723 0.05093 0.29633 0.00356 0.968835 1632.7 19.89 1673.1 17.68 102 I05_9_26 4.12165 0.04968 0.30249 0.00366 0.996186 1601.7 18.6 1703.6 18.11 106 I05_9_27 4.03217 0.05218 0.2917 0.00379 0.996007 1627.8 18.77 1650 18.89 101 I05_10_28 3.87458 0.04962 0.26847 0.00346 0.993692 1707.8 18.44 1533.1 17.6 90 I05_10_29 3.61162 0.0488 0.26753 0.00366 0.987664 1584.3 18.93 1528.2 18.62 96 I05_10_30 4.27499 0.0541 0.3082 0.0038 0.974291 1634.5 19.71 1731.8 18.74 106 I05_11_31 4.81412 0.06632 0.297 0.00367 0.896978 1918.1 22.04 1676.4 18.26 87 I05_11_32 7.68019 0.10186 0.36669 0.00496 0.980503 2367.7 16.97 2013.8 23.42 85 I05_11_33 9.26369 0.11139 0.42948 0.00505 0.977882 2416.3 18.04 2303.4 22.77 95 I05_12_34 6.40732 0.08524 0.34028 0.00459 0.986259 2184.3 17.3 1888 22.07 86 I05_12_35 4.08075 0.05203 0.2889 0.00373 0.987535 1668.6 18.41 1636 18.64 98 I05_12_36 4.07406 0.05347 0.30002 0.00399 0.98687 1595.4 18.47 1691.4 19.79 106 I05_13_37 4.0843 0.05239 0.2931 0.00376 0.999905 1643.4 18.79 1657 18.76 101 I05_13_38 6.73772 0.09199 0.34811 0.00486 0.97793 2232.1 17.42 1925.5 23.26 86 I05_13_39 8.26597 0.101 0.40455 0.00482 0.975096 2324.6 18.31 2190 22.12 94 I05_14_40 4.02498 0.05076 0.27292 0.00344 0.999459 1748.1 18.47 1555.6 17.41 89 I05_14_41 3.92403 0.04904 0.28283 0.00355 0.99567 1635.5 18.58 1605.6 17.82 98 I05_15_42 3.96078 0.05161 0.28962 0.00376 0.996337 1608.7 19.12 1639.6 18.82 102 I05_17_43 6.12045 0.0731 0.36304 0.00431 0.994005 1988.7 18.01 1996.6 20.4 100 I05_17_44 3.89847 0.04951 0.284 0.00365 0.988153 1615.6 18.42 1611.5 18.34 100 I05_17_45 4.0751 0.05073 0.29925 0.00375 0.993412 1600.8 18.49 1687.6 18.62 105 I05_19_46 14.81536 0.18793 0.55609 0.00711 0.992109 2769.3 16.68 2850.5 29.44 103 I05_19_47 9.90962 0.12499 0.45243 0.00578 0.987283 2443 16.86 2406 25.64 98 I05_19_48 4.11814 0.05328 0.30557 0.00405 0.976155 1581.5 18.35 1718.9 20 109 I05_20_49 4.05119 0.05097 0.30194 0.00387 0.981616 1573.1 18.42 1700.9 19.16 108 I05_20_50 4.06231 0.05052 0.29315 0.00371 0.982667 1633 18.26 1657.3 18.47 101 I05_21_51 4.16421 0.05217 0.3004 0.00383 0.982629 1633.9 18.28 1693.3 19 104 I05_21_52 3.87181 0.04561 0.27425 0.00321 0.993602 1668.1 18.94 1562.3 16.23 94 I05_21_53 8.48065 0.11612 0.40589 0.00571 0.973308 2363.2 17.25 2196.1 26.16 93 I05_22_54 3.84316 0.04856 0.27723 0.00352 0.995148 1634 18.88 1577.4 17.75 97 I05_22_55 3.70251 0.04998 0.27567 0.00384 0.969077 1575.1 18.5 1569.5 19.42 100 I05_25_56 3.87119 0.04806 0.27207 0.00343 0.98475 1682.4 18.29 1551.3 17.38 92 I05_25_57 6.55654 0.08926 0.35002 0.00485 0.982502 2175 17.89 1934.7 23.17 89
Analysis_# Pb207/Pb206 Pb206/U238 Pb207/U235 Pb207/Pb206 Pb206/U238 Pb207/U235 Pb204 Pb206 Pb207 U238 m1 0.09823 0.00105 0.26682 0.00367 3.61445 0.05048 1590.8 19.82 1524.7 18.68 1552.7 11.11 12 120643 12034 616459 98 m11 0.09874 0.00188 0.26383 0.00408 3.59256 0.07285 1600.4 35.16 1509.4 20.8 1547.9 16.11 0 7533 757 38959 97 m12 0.09865 0.00143 0.25856 0.00373 3.51744 0.05878 1598.8 26.82 1482.5 19.13 1531.1 13.21 0 19489 1948 102885 96 m12_2 0.09933 0.00127 0.2666 0.00377 3.65171 0.05671 1611.6 23.69 1523.5 19.2 1560.9 12.38 0 41506 4158 212984 97 m13 0.09876 0.00133 0.26428 0.00377 3.6 0.05741 1600.9 24.92 1511.7 19.24 1549.5 12.67 6 29670 2978 153518 97 m14 0.09396 0.00299 0.21395 0.00404 2.77268 0.08625 1507.4 58.86 1249.8 21.44 1348.2 23.21 0 4357 423 27834 89 m15 0.09858 0.00128 0.24401 0.00346 3.31834 0.0515 1597.4 24.03 1407.5 17.92 1485.4 12.11 2 26956 2721 150827 93 m16 0.09797 0.00117 0.26272 0.0037 3.54909 0.05294 1585.9 22.14 1503.8 18.86 1538.2 11.82 0 74692 7428 390730 97 m17 0.10622 0.00514 0.18547 0.00467 2.71922 0.12375 1735.5 86.12 1096.8 25.39 1333.7 33.78 14 1643 185 12028 77 m18 0.09803 0.00122 0.26913 0.00379 3.64089 0.05541 1587 23.14 1536.4 19.27 1558.5 12.12 10 39645 3962 201352 98 m2 0.09779 0.00162 0.23783 0.00355 3.20981 0.05874 1582.4 30.75 1375.4 18.47 1459.5 14.17 16 12451 1246 71643 92 m20 0.12414 0.00236 0.25627 0.00408 4.38749 0.08829 2016.5 33.39 1470.7 20.95 1710 16.64 45 11085 1405 59650 85 m21 0.09808 0.00136 0.2713 0.00394 3.65828 0.05905 1588 25.71 1547.4 19.96 1562.3 12.87 39 71215 7282 361884 98 m22 0.09804 0.0012 0.27038 0.00381 3.655 0.05518 1587.2 22.68 1542.7 19.35 1561.6 12.04 0 53885 5373 273515 98 m23 0.09787 0.00139 0.25939 0.00375 3.50438 0.05762 1583.9 26.25 1486.7 19.18 1528.2 12.99 0 21798 2187 115163 96 m24 0.28701 0.0053 0.35974 0.00624 14.23784 0.27016 3401.5 28.43 1980.9 29.58 2765.7 18 25 2068 603 7891 81 m25 0.11665 0.00201 0.20536 0.00305 3.30065 0.061 1905.5 30.64 1204 16.32 1481.2 14.4 10 6621 778 42973 78 m27 0.09237 0.0014 0.24359 0.00359 3.10342 0.05361 1475 28.59 1405.4 18.59 1433.5 13.27 0 15769 1498 89575 97 m28 0.09777 0.00179 0.24482 0.00378 3.30117 0.06511 1582.1 33.81 1411.7 19.6 1481.3 15.37 8 9126 916 51678 94 m29 0.09852 0.00114 0.25617 0.00362 3.47981 0.05143 1596.3 21.45 1470.2 18.55 1522.6 11.66 31 57677 5760 311980 95 m30 0.09784 0.00117 0.25805 0.00366 3.48099 0.05217 1583.4 22.13 1479.8 18.73 1522.9 11.82 0 37993 3781 203884 96 m4 0.28658 0.01522 0.33994 0.01262 13.42689 0.62772 3399.2 80.33 1886.4 60.74 2710.2 44.18 2 388 112 1557 80 m5 0.09728 0.00115 0.26849 0.00383 3.60076 0.05398 1572.7 22.03 1533.1 19.48 1549.7 11.91 0 49879 4969 259345 99 m5_2 0.09824 0.0012 0.27337 0.0039 3.70251 0.05648 1591 22.65 1557.9 19.75 1571.9 12.19 14 35389 3529 179965 99 m6 0.09799 0.00154 0.26655 0.00399 3.60033 0.06424 1586.2 29.1 1523.3 20.29 1549.6 14.18 0 13208 1313 69054 98 m6_2 0.09671 0.00119 0.27281 0.00394 3.63477 0.05589 1561.5 22.88 1555 19.94 1557.2 12.24 14 47724 4721 245766 100 m7 0.09821 0.0011 0.27215 0.00389 3.68283 0.05398 1590.4 20.85 1551.7 19.71 1567.7 11.7 5 72398 7292 374281 99 m8 0.10711 0.00215 0.24934 0.00398 3.68308 0.07774 1750.7 36.19 1435 20.55 1567.7 16.86 1 10188 1109 56528 90 m8_2 0.09771 0.00139 0.27752 0.00407 3.73833 0.06273 1580.9 26.42 1578.8 20.55 1579.6 13.44 2 8236 815 41422 100 Monazite BH08
Analysis_# Pb207/Pb206 Pb206/U238 Pb207/U235 Pb207/Pb206 Pb206/U238 Pb207/U235 Pb204 Pb206 Pb207 U238 09_10 0.0967 0.001 0.27532 0.00385 3.67039 0.05089 1561.5 19.24 1567.7 19.48 1565 11.06 13 204933 20486 1035137 100 09_11 0.10384 0.00159 0.2885 0.00429 4.12962 0.0719 1693.9 27.89 1634 21.45 1660.2 14.23 4 16216 1721 78007 104 09_12 0.09762 0.00107 0.28 0.00393 3.76764 0.05391 1579.1 20.3 1591.4 19.8 1585.9 11.48 0 84203 8393 417151 99 09_13 0.09836 0.0013 0.26699 0.00386 3.6201 0.05769 1593.2 24.52 1525.5 19.64 1554 12.68 17 33254 3343 173213 104 09_14 0.09718 0.00138 0.26874 0.00393 3.59984 0.0601 1570.6 26.37 1534.4 19.95 1549.5 13.27 28 21916 2161 113429 102 09_15 0.10025 0.00183 0.28143 0.0044 3.89142 0.0768 1628.7 33.64 1598.5 22.12 1611.9 15.94 0 17513 1830 86876 102 09_15_2 0.12029 0.00241 0.28892 0.00471 4.79098 0.10135 1960.5 35.36 1636.1 23.54 1783.3 17.77 42 8443 1037 40863 120 09_16 0.10016 0.00287 0.28174 0.00507 3.88985 0.11198 1627.1 52.41 1600.1 25.48 1611.6 23.25 8 3637 369 18019 102 09_16_2 0.09925 0.00111 0.27808 0.00394 3.80463 0.05583 1610.1 20.75 1581.7 19.87 1593.7 11.8 0 86215 8639 433134 102 09_17 0.09955 0.00117 0.27839 0.00397 3.82025 0.05736 1615.7 21.79 1583.2 20.03 1597 12.08 6 59784 6044 299980 102 09_19 0.10043 0.0017 0.26771 0.00409 3.70608 0.06969 1632 31.1 1529.2 20.79 1572.7 15.04 0 15146 1545 79227 107 09_2 0.09952 0.00112 0.27364 0.00389 3.75392 0.05536 1615.1 20.81 1559.2 19.69 1583 11.82 9 89019 8941 456003 104 M21 0.09687 0.00121 0.282 0.0041 3.76672 0.05859 1564.8 23.22 1601.4 20.61 1585.7 12.48 13 35452 3526 177485 98 M22 0.09696 0.00119 0.26736 0.00388 3.57459 0.05511 1566.5 22.86 1527.4 19.74 1543.9 12.23 18 38128 3804 201529 103 M23 0.09796 0.00138 0.28319 0.0042 3.82478 0.06402 1585.7 26.16 1607.4 21.12 1598 13.47 0 23265 2341 116140 99 M3 0.09913 0.00106 0.27213 0.0039 3.71927 0.05341 1607.8 19.86 1551.6 19.75 1575.5 11.49 9 104589 10722 544562 104 m4 0.09707 0.001 0.27819 0.00388 3.72364 0.0513 1568.5 19.1 1582.2 19.55 1576.5 11.03 20 154466 15495 769200 99 m5 0.09651 0.00113 0.27355 0.00387 3.64063 0.05347 1557.8 21.83 1558.8 19.6 1558.5 11.7 27 40254 4045 203612 100 m6 0.09903 0.00138 0.2736 0.00397 3.73642 0.0609 1606 25.79 1559 20.1 1579.2 13.06 6 18007 1847 90856 103 m6_2 0.10067 0.00162 0.2477 0.0037 3.43884 0.0614 1636.6 29.66 1426.6 19.11 1513.3 14.04 26 12045 1270 66984 115 m7 0.09646 0.00104 0.26905 0.00374 3.57879 0.05025 1556.7 20.17 1536 19.02 1544.8 11.14 0 76970 7682 393341 101 m8 0.09655 0.0013 0.27511 0.00394 3.66298 0.0582 1558.4 25.08 1566.7 19.93 1563.3 12.67 0 18858 1886 94030 99 m9 0.09634 0.00102 0.27563 0.0038 3.662 0.0504 1554.5 19.71 1569.3 19.21 1563.1 10.98 0 85741 8577 424685 99 M23 0.09476 0.00175 0.26115 0.00392 3.41243 0.06708 1523.4 34.35 1495.7 20.02 1507.3 15.44 0 9968 960 51166 102 M24 0.0982 0.0017 0.2701 0.004 3.6572 0.06835 1590.2 31.93 1541.3 20.3 1562.1 14.9 8 15719 1569 78030 103 M25 0.09765 0.00116 0.27488 0.00377 3.70112 0.05383 1579.7 21.97 1565.5 19.08 1571.6 11.63 5 71029 7051 346552 101 M26 0.0992 0.00153 0.26593 0.00383 3.63753 0.06254 1609.1 28.41 1520.1 19.52 1557.8 13.69 0 27376 2760 138096 106 M27 0.10484 0.00226 0.27896 0.00445 4.03288 0.08953 1711.6 39.13 1586.1 22.44 1640.9 18.06 12 7670 817 36892 108 M28 0.10018 0.00138 0.26261 0.0037 3.62754 0.05779 1627.4 25.31 1503.2 18.89 1555.6 12.68 0 34201 3481 174785 108 M29 0.09759 0.0015 0.25276 0.00364 3.40122 0.05854 1578.6 28.54 1452.7 18.73 1504.7 13.51 0 22507 2231 119538 109 M30 0.09641 0.00113 0.26922 0.00369 3.57906 0.05188 1555.9 21.85 1536.8 18.76 1544.9 11.5 40 61106 5983 304765 101 M31 0.09928 0.00138 0.26845 0.00379 3.67499 0.059 1610.7 25.64 1532.9 19.27 1566 12.82 0 38105 3841 190643 105 M32 0.09935 0.00124 0.27664 0.00384 3.7895 0.05705 1611.9 23.13 1574.4 19.38 1590.5 12.09 4 65165 6573 316447 102 M32_2 0.09751 0.0011 0.27689 0.00378 3.72267 0.05271 1577 20.87 1575.7 19.08 1576.3 11.33 0 96777 9579 469645 100 M33 0.09902 0.00118 0.27474 0.00373 3.75078 0.05347 1605.7 22.01 1564.8 18.87 1582.3 11.43 0 34279 3537 164724 103 M34 0.09833 0.00132 0.2657 0.00369 3.60161 0.05549 1592.7 24.96 1518.9 18.8 1549.9 12.24 0 20547 2116 102219 105 M35 0.09451 0.0019 0.27494 0.0042 3.58121 0.07433 1518.2 37.44 1565.8 21.25 1545.4 16.47 22 5456 547 26198 97 M36 0.0939 0.00104 0.26757 0.00359 3.46293 0.0468 1506.2 20.82 1528.4 18.26 1518.8 10.65 0 44155 4419 217113 99 M38 0.09436 0.00129 0.26469 0.00367 3.44184 0.05282 1515.3 25.55 1513.8 18.72 1514 12.07 11 15654 1592 77686 100 M39 0.0955 0.00341 0.24962 0.0049 3.28435 0.11335 1538 65.71 1436.5 25.26 1477.4 26.86 13 2314 239 12176 107 M40 0.09352 0.00172 0.25345 0.00374 3.26766 0.06295 1498.4 34.47 1456.2 19.22 1473.4 14.98 0 6492 643 33466 103 M41 0.09129 0.00144 0.2524 0.00357 3.17599 0.05406 1452.5 29.74 1450.8 18.36 1451.3 13.14 2 12515 1214 64510 100 M42 0.09425 0.00096 0.25944 0.00339 3.37112 0.04298 1513.2 19.19 1487 17.35 1497.7 9.98 11 119912 11995 598385 102 M43 0.09319 0.00107 0.2592 0.00346 3.3294 0.04528 1491.8 21.67 1485.7 17.69 1488 10.62 19 49629 4996 248367 100 Bh09
Analysis_# Pb207/Pb206 Pb206/U238 Pb207/U235 Pb207/Pb206 Pb206/U238 Pb207/U235 Pb204 Pb206 Pb207 U238 1_1 0.09353 0.00157 0.3057 0.00551 3.94201 0.08311 1498.6 31.51 1719.5 27.21 1622.3 17.08 19 30441 2883 169642 115 1_2 0.097 0.0012 0.33031 0.00571 4.42038 0.07936 1567.1 23.02 1839.9 27.68 1716.2 14.87 1 37537 3749 192631 117 1_3 0.09473 0.00122 0.32181 0.0056 4.20373 0.07638 1522.8 24.01 1798.5 27.3 1674.7 14.9 0 36113 3551 190597 118 1_4 0.09877 0.00116 0.32401 0.00555 4.41136 0.07806 1601.1 21.75 1809.3 27.01 1714.5 14.65 0 51916 5188 270580 113 1_5 0.098 0.00115 0.32692 0.0056 4.42053 0.07844 1586.5 21.71 1823.5 27.21 1716.2 14.69 3 60190 5950 311321 115 1_6 0.09905 0.00123 0.32687 0.00567 4.46373 0.08035 1606.3 22.94 1823.2 27.54 1724.3 14.93 3 45233 4608 235171 114 1_7 0.09863 0.00123 0.32057 0.00556 4.35874 0.07901 1598.3 23.12 1792.5 27.13 1704.6 14.97 0 52764 5312 279625 112 1_8 0.09791 0.00112 0.30711 0.00523 4.14896 0.07179 1584.7 21.15 1726.5 25.82 1664 14.16 0 49322 4959 270456 109 1_9 0.09769 0.00147 0.3048 0.00541 4.10725 0.08204 1580.5 27.94 1715.1 26.75 1655.7 16.31 0 34447 3381 192677 109 1_10 0.099 0.00131 0.31074 0.00542 4.24171 0.07779 1605.4 24.47 1744.4 26.66 1682.1 15.07 14 28046 2891 153044 109 2_11 0.09717 0.00113 0.29515 0.00493 3.95002 0.06871 1570.5 21.6 1667.2 24.56 1624 14.09 1 42900 4167 240060 106 2_12 0.09941 0.00152 0.32599 0.00559 4.45875 0.08682 1613.1 28.25 1818.9 27.17 1723.3 16.15 0 31618 3168 158414 113 2_13 0.09888 0.0013 0.30598 0.00515 4.16775 0.07618 1603.1 24.34 1720.9 25.45 1667.7 14.97 6 75864 7469 407224 107 2_14 0.09915 0.0017 0.31808 0.00557 4.32591 0.08812 1608.3 31.71 1780.4 27.24 1698.3 16.8 2 26020 2701 133108 111 2_15 0.0997 0.00131 0.30844 0.00518 4.22767 0.07634 1618.4 24.31 1733 25.5 1679.4 14.83 11 57358 5760 303755 107 2_16 0.0997 0.00117 0.3154 0.00525 4.33348 0.07509 1618.5 21.72 1767.2 25.71 1699.8 14.3 6 79008 7908 410870 109 2_17 0.09975 0.00125 0.30757 0.00515 4.2222 0.07487 1619.4 23.05 1728.7 25.38 1678.3 14.56 12 56790 5691 302783 107 2_18 0.09331 0.00126 0.25202 0.00426 3.23839 0.05977 1494.2 25.29 1448.9 21.94 1466.4 14.32 0 41679 3894 272270 97 3_19 0.10008 0.00133 0.30097 0.0051 4.14819 0.07594 1625.5 24.5 1696.1 25.26 1663.9 14.98 9 36225 3642 198335 104 3_20 0.09935 0.00125 0.31179 0.00525 4.26679 0.07643 1611.9 23.35 1749.5 25.79 1687 14.73 0 36755 3666 194195 109 3_21 0.09946 0.00143 0.31153 0.0053 4.26562 0.08027 1613.9 26.48 1748.2 26.03 1686.8 15.48 0 42447 4268 222873 108 3_22 0.09907 0.00122 0.31351 0.0054 4.28269 0.07691 1606.8 22.7 1757.9 26.52 1690 14.78 4 42608 4301 229974 109 3_23 0.09876 0.00118 0.31084 0.00534 4.23281 0.0751 1600.9 22.07 1744.8 26.27 1680.4 14.57 6 49834 5019 271211 109 3_24 0.09881 0.00118 0.31236 0.00538 4.25426 0.07646 1601.9 22.14 1752.3 26.45 1684.6 14.78 0 48176 4789 261980 109 3_25 0.09898 0.00127 0.31448 0.00543 4.293 0.07824 1605 23.7 1762.7 26.63 1692 15.01 1 39873 4027 213866 110 3_26 0.09898 0.00114 0.31024 0.00534 4.23379 0.07534 1605.1 21.36 1741.9 26.29 1680.6 14.62 3 46984 4671 257862 109 3_27 0.09844 0.00112 0.29518 0.00509 4.00634 0.07116 1594.8 21.14 1667.3 25.32 1635.5 14.43 1 50823 5021 293742 105 3_28 0.09885 0.00125 0.31237 0.00539 4.25552 0.0776 1602.5 23.47 1752.3 26.5 1684.8 14.99 1 29096 2916 157427 109 3_29 0.09881 0.00122 0.31606 0.00547 4.30574 0.07845 1601.8 22.78 1770.5 26.82 1694.5 15.01 5 27668 2749 149012 111 3_30 0.09871 0.00127 0.31526 0.00546 4.29014 0.07901 1599.9 23.86 1766.5 26.78 1691.5 15.17 12 23598 2356 126758 110 3_31 0.09902 0.00138 0.28138 0.00492 3.8396 0.07311 1605.7 25.7 1598.3 24.73 1601.1 15.34 0 21377 2139 128652 100 3_32 0.09902 0.00129 0.29942 0.0052 4.087 0.07586 1605.7 24.05 1688.4 25.82 1651.7 15.14 14 21719 2168 123172 105 3_33 0.09903 0.00136 0.32685 0.00572 4.46149 0.08453 1605.9 25.44 1823.1 27.78 1723.8 15.72 0 25153 2527 130512 114 4_34 0.09769 0.00129 0.31017 0.0053 4.1792 0.07678 1580.4 24.58 1741.5 26.09 1669.9 15.05 0 20270 2006 108769 110 4_35 0.09088 0.00143 0.24867 0.00434 3.11651 0.06179 1443.9 29.69 1431.6 22.4 1436.8 15.24 0 21655 2029 144806 99 4_36 0.09685 0.00149 0.31006 0.00542 4.13709 0.08154 1564.2 28.53 1741 26.68 1661.7 16.12 9 29517 2915 158888 111 4_37 0.09929 0.00159 0.33359 0.0059 4.56491 0.09201 1610.9 29.49 1855.7 28.5 1742.9 16.79 21 24803 2515 124438 115 4_38 0.09875 0.00135 0.32855 0.00566 4.47279 0.08309 1600.7 25.23 1831.4 27.44 1725.9 15.42 0 42580 4289 216186 114 4_39 0.09331 0.00145 0.31472 0.0055 4.05003 0.08022 1494.3 29.08 1763.9 26.99 1644.3 16.13 0 31494 3006 166911 118 4_40 0.09681 0.00153 0.32993 0.0058 4.40278 0.08793 1563.5 29.41 1838.1 28.11 1712.9 16.53 0 27734 2756 140134 118 BH10
Analysis_# Pb207/Pb206 Pb206/U238 Pb207/U235 Pb207/Pb206 Pb206/U238 Pb207/U235 Pb204 Pb206 Pb207 U238 37_23 0.09717 0.00099 0.27272 0.00387 3.65347 0.05116 1570.4 18.91 1554.6 19.62 1561.3 11.16 18 163450 16365 847411 99 39_24 0.09859 0.00112 0.2833 0.00408 3.85051 0.05687 1597.6 21 1607.9 20.48 1603.4 11.91 14 41727 4238 208411 101 39_25 0.09744 0.00106 0.26393 0.00378 3.54588 0.05136 1575.8 20.21 1509.9 19.27 1537.5 11.47 13 69878 6998 374631 96 43_28 0.09757 0.00097 0.2551 0.00362 3.43154 0.04761 1578.2 18.47 1464.7 18.59 1511.6 10.91 25 326122 32796 1809627 93 47_30 0.09861 0.00099 0.26202 0.00373 3.5618 0.04947 1598.1 18.62 1500.2 19.07 1541.1 11.01 78 206419 21193 1117502 94 47_31 0.0993 0.00102 0.27449 0.00392 3.75759 0.05303 1610.9 19.07 1563.6 19.81 1583.7 11.32 36 115868 11877 598488 97 55_32 0.09956 0.00118 0.27539 0.004 3.78018 0.05725 1615.9 21.84 1568.1 20.19 1588.5 12.16 22 36579 3743 188513 97 55_32_2 0.09984 0.00115 0.27251 0.00395 3.75082 0.05587 1621.2 21.25 1553.6 20 1582.3 11.94 37 38359 3966 200066 96 63_33_2 0.09326 0.00137 0.16783 0.00251 2.15793 0.03704 1493.2 27.48 1000.1 13.84 1167.6 11.91 0 15515 1487 131406 67 63_33 0.09349 0.00134 0.22776 0.0034 2.935 0.04953 1497.8 26.85 1322.7 17.86 1391 12.78 5 15623 1517 97573 88 8_7 0.09835 0.00109 0.27876 0.00403 3.77908 0.05527 1593.1 20.53 1585.1 20.3 1588.3 11.74 7 54231 5528 276947 99 8_7_2 0.10119 0.00113 0.28017 0.00404 3.90836 0.05754 1646 20.51 1592.2 20.35 1615.4 11.9 22 47944 4983 243302 97 41_27 0.10331 0.0011 0.29824 0.00427 4.24835 0.06124 1684.4 19.46 1682.6 21.22 1683.4 11.85 24 104067 10989 495755 100 47_29 0.09749 0.00098 0.25767 0.00367 3.46377 0.04872 1576.7 18.73 1477.9 18.83 1519 11.08 2 282811 28239 1560277 94 64_34 0.10407 0.00146 0.27056 0.00403 3.88214 0.06502 1697.9 25.63 1543.6 20.46 1610 13.52 0 27977 2965 146794 91 7_4 0.10284 0.00113 0.28779 0.00414 4.08078 0.05997 1676 20.21 1630.5 20.72 1650.5 11.98 51 85161 8917 420273 97 7_5 0.09891 0.001 0.26558 0.00379 3.62207 0.05124 1603.7 18.71 1518.3 19.31 1554.4 11.26 10 401167 40413 2150582 95 8_6 0.09829 0.00113 0.28153 0.00408 3.81522 0.05746 1591.9 21.35 1599.1 20.5 1596 12.12 0 63573 6353 321339 100 11_8 0.09793 0.00099 0.26854 0.00385 3.62585 0.05138 1585 18.86 1533.4 19.55 1555.2 11.28 25 210259 21085 1117406 97 11_9 0.09674 0.00098 0.24606 0.00352 3.28194 0.04658 1562.2 18.87 1418.1 18.21 1476.8 11.05 20 310336 30569 1799064 91 m10 0.10089 0.00199 0.28021 0.00468 3.89922 0.08373 1640.5 36.1 1592.4 23.55 1613.5 17.35 3 9967 1029 52679 97 m10_2 0.1062 0.00167 0.3869 0.00619 5.66599 0.10433 1735.1 28.53 2108.4 28.76 1926.2 15.89 2 14299 1572 54947 122 m11 0.09847 0.00103 0.26259 0.00392 3.56716 0.05288 1595.3 19.32 1503.1 20.04 1542.3 11.76 4 113497 11537 641773 94 m12 0.11891 0.00754 0.3882 0.01337 6.36854 0.38037 1939.9 109.3 2114.5 62.09 2027.9 52.41 0 687 85 2635 109 m12_2 0.09767 0.00144 0.27038 0.00422 3.64438 0.06436 1580.2 27.29 1542.7 21.44 1559.3 14.07 0 13050 1318 71536 98 m13 0.09776 0.00108 0.2724 0.00411 3.67385 0.05574 1581.7 20.47 1553 20.82 1565.7 12.11 26 64371 6547 351988 98 m15 0.09663 0.00104 0.26634 0.004 3.55141 0.05316 1560.1 20.01 1522.2 20.38 1538.7 11.86 0 71201 7170 397619 98 m17 0.09863 0.0014 0.25888 0.00407 3.5225 0.06095 1598.4 26.25 1484.1 20.84 1532.3 13.69 0 25019 2589 144961 93 m17_2 0.09657 0.00152 0.25051 0.00398 3.33903 0.06159 1558.8 29.31 1441.1 20.54 1490.2 14.41 16 27045 2720 160940 92 m18 0.1002 0.00191 0.28296 0.00462 3.92397 0.08181 1627.8 35.01 1606.3 23.22 1618.6 16.87 13 14481 1487 74582 99 m19 0.13413 0.01397 0.49318 0.02832 9.12494 0.88536 2152.7 171.36 2584.4 122.25 2350.6 88.79 13 291 41 885 120 m22 0.09606 0.0014 0.28798 0.00456 3.81874 0.06718 1548.9 27.17 1631.4 22.82 1596.7 14.16 0 28875 2929 150710 105 m22_2 0.10025 0.00115 0.28944 0.00446 4.00441 0.06195 1628.8 21.17 1638.7 22.32 1635.1 12.57 38 54116 5776 282865 101 BH16