U–Pb zircon geochronology in the western part of the Rayner Complex, East Antarctica

Abstract

U-Pb zircon geochronology was applied to nine metasedimentary samples collected from Mt. Yuzhnaya, Condon Hills, and Mt. Lira in the inland region of the Rayner Complex of western Enderby Land, East Antarctica, in order to define the eastern limits of the western Rayner Complex that underwent the Pan-African metamorphism and to evaluate potential source areas of metasedimentary rocks. Condon Hills and Mt. Lira revealed metamorphic ages of~894 and~934 Ma, respectively, which are consistent with previously reported metamorphism in association with Rayner Structural Episode (RSE). Mt. Yuzhnaya samples affected by the RSE contain zircon grains rejuvenated during 590-570 Ma, which indicates that the Pan-African reworking can be extended up to Mt. Yuzhnaya. On the other hand, the Condon Hills samples include Archean detritus, and the age peaks from 3850 to 2491 Ma are the oldest components in the Rayner Complex of western Enderby Land. There is no evidence of reworked Napier Complex rocks in the studied Rayner samples.

Tectonothermal evolution of a collisional orogen in the Khammam region, southeastern India: insights from structures, phase equilibria modeling and U–Th–(total) Pb monazite geochronology

“…These authors also postulated that the formation of the Ongole Domain occurred in the near vicinity of the Napier Complex during Late Paleoproterozoic to Early Mesoproterozoic (Henderson et al 2014). This inference is based on the sporadically preserved similar ages in the Rayner-Napier complex on account of felsic magmatism and UHT metamorphism (Kelly et al 2002;Halpin et al 2005Halpin et al , 2013Horie et al 2016). Therefore, our new data from the Khammam region support that the Neoarchean components in the Ongole Domain were possibly derived from the Rayner-Napier Complex of East Antarctica.…”

The impact of the Pan-African-aged tectonothermal event on high-grade rocks at Mount Brown, East Antarctica

“…The recent reports of zircon age records of c . 590–500 Ma in limited outcrops in the Enderby, Wilhelm II and Queen Mary lands indicate that the western and eastern parts of the Rayner Complex were also reworked during the Pan-African-aged event (Mikhalsky et al 2015, Horie et al 2016, Daczko et al 2018, this paper). However, the metamorphic grade of Pan-African-aged reworking varies between different areas or terranes, from granulite facies in the Rayner Complex in Prydz Bay (760–860°C and 6–7 kbar; Fitzsimons 1996, Carson et al 1997) and the northern Prince Charles Mountains (800–870°C and 5.5–6.5 kbar; Morrissey et al 2016), to upper amphibolite facies in the Lambert Terrane (650–700°C and 6–7 kbar; Boger & Wilson 2005), lower amphibolite facies in the Ruker Terrane (565–640°C and 4–5.2 kbar; Phillips et al 2007) and the Fisher Terrane (550–615°C and 2.5–4.0 kbar; Van Leeuwen et al 2019) and greenschist facies in a subglacial Archean block south-east of the Vestfold Hills (chloritoid grade; our unpublished data).…”

“…The available data suggest that the Pan-African-aged tectonothermal event affected the vast outcrops in the Prince Charles Mountains-Prydz Bay region (Liu et al 2013). The recent reports of zircon age records of c. 590-500 Ma in limited outcrops in the Enderby, Wilhelm II and Queen Mary lands indicate that the western and eastern parts of the Rayner Complex were also reworked during the Pan-African-aged event (Mikhalsky et al 2015, Horie et al 2016, Daczko et al 2018. However, the metamorphic grade of Pan-African-aged reworking varies between different areas or terranes, from granulite facies in the Rayner Complex in Prydz Bay (760-860°C and 6-7 kbar; Fitzsimons 1996, Carson et al 1997 Phillips et al 2007) and the Fisher Terrane (550-615°C and 2.5-4.0 kbar; Van Leeuwen et al 2019) and greenschist facies in a subglacial Archean block south-east of the Vestfold Hills (chloritoid grade; our unpublished data).…”

Nanoscale features revealed by a multiscale characterisation of discordant monazite highlight mobility mechanisms of Th and Pb

“…The monazite host that lacks Pb*-bearing nanophases has been dated by atom probe at 1.02 ±0.26 Ga (Turuani et al 2022), corresponding within error to the lower intercept of the discordia formed by the total monazite dataset, at 1.09-1.05 Ga (ID-TIMS and LA-ICP-MS respectively; Black et al 1984, Turuani et al 2022. This age reflects the amphibolite facies retrogression associated with reworking during the Rayner Structural Episode (Black et al, 1983(Black et al, , 1987Kelly et al 2000Kelly et al , 2002Halpin et al 2005;Horie et al 2016), which induced resetting of the U-Th-Pb chronometers at the nanoscale in monazite (Turuani et al 2022). Some Pb*-bearing nanophases have an isotopic signature corresponding to Pb* formed between 2.44 ±0.04 and 1.02 ±0.26 Ga and isolated as nanoreservoirs at ca.…”

“…Later localized upright mylonitic shear zones (Sheraton et al 1980;Black et al 1983aBlack et al , b, 1987Sandiford and Wilson 1983;Sandiford 1985) are inferred to be related to the ca. 1 Ga Rayner Structural Episode (Kelly et al 2000(Kelly et al , 2002Halpin et al 2005;Horie et al 2016) which also caused spatially focused and variable retrogression of rocks under amphibolite conditions. Localized pegmatites intruded the basement near Zircon Point at ca.…”