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Accurately defining the peak ages and timescales of high‐temperature metamorphism is fundamental to unravelling tectonic dynamics. However, metamorphic constraints are frequently hampered by a large spread of zircon U–Pb ages without explicit textural relationships. Integrated garnet and zircon petrochronology may clarify ambiguous ages retrieved from ancient high‐temperature metamorphic rocks. There is a long‐standing debate on the interpretation of the spread of zircon ages from c. 2.5–1.8 Ga for the granulites of the North China Craton. In order to clarify the timing and duration of (ultra)high‐temperature metamorphism in the North China Craton, we investigated a mafic granulite and the adjoining gneiss from the Yinshan Block of the North China Craton using zircon and titanite U–Pb geochronology combined with garnet Lu–Hf and Sm–Nd geochronology. Pseudosection modelling and conventional thermobarometric calculations constrain the peak metamorphic conditions to be ~1.0 GPa and ~850°C. The near‐complete lack of major‐element zoning in garnet, aside from ~2 μm diffusion profiles at crystal rims, suggests complete re‐equilibration at peak temperatures followed by fast cooling from high temperatures. The Lu–Hf garnet age of 1870 ± 4 Ma and Sm–Nd age of 1870 ± 7 Ma, determined on the same garnet fractions, are indistinguishable from the zircon U–Pb age of 1866 ± 11 Ma obtained from zircon that grew contemporaneously with garnet, evidenced by the chemical equilibrium of coexisting garnet and zircon, and are additionally consistent with a titanite U–Pb age of 1876 ± 7 Ma. We interpret this close agreement of ages, within uncertainty, coupled to the existence of flat Sm–Nd–Hf profiles in garnet that also has well‐preserved Lu zoning, to reflect a short‐lived high‐temperature metamorphic event that was terminated by rapid exhumation and cooling. The short‐lived (<4 Myr) high‐temperature metamorphism may be generated in the lowermost parts of the crust through magmatic underplating/intraplating during extension that follows collision of the Ordos and the Yinshan Blocks. [ABSTRACT FROM AUTHOR]

The recognition of the Indosinian Orogeny in the South China block has been controversial and difficult because of strong weathering and thick cover. High temperature (HT) and high pressure (HP) metamorphic rocks related to this orogeny were considered to be absent from this orogenic belt until the recent discovery of eclogite and granulite facies meta–igneous rocks, occurring as lenses within the meta–sedimentary rocks of the Badu Complex. However, metamorphic state of these meta–sedimentary rocks is still not clear. Besides, there have been no geochronological data of HT pelitic granulites previously reported from the Badu Complex. This paper presents petrographic characteristics and zircon geochronological results on the newly discovered kyanite garnet gneiss, pyroxene garnet gneiss and the HT pelitic granulites (sillimanite garnet gneiss). Mineral assemblages are garnet + sillimanite + ternary feldspar + plagioclase + quartz + biotite for the HT pelitic granulite, kyanite + ternary feldspar + garnet + sillimanite + plagioclase + quartz + biotite for the kyanite garnet gneiss, and garnet + biotite + pyroxene + plagioclase + ternary feldspar + quartz for the pyroxene garnet gneiss, respectively. Decompressional coronas around garnet grains can be observed in all these pelitic rocks. Typical granulite facies mineral assemblages and reaction textures suggest that these rocks experienced HP granulite facies metamorphism and overprinted decompression along a clockwise P–T loop. Results from integrated U–Pb dating and REE analysis indicate the growth of metamorphic zircons from depleted heavy REE sources (100–50 chondrite) compared with detrital zircons derived from granitic sources (typically > 1000 chondrite). Metamorphic zircons in HP granulite exhibit no or subdued negative Eu anomalies, which perhaps indicate zircon overgrowth under eclogite facies conditions. The zircon overgrowth ages range from 250 to 235 Ma, suggesting that HP granulite (eclogite) to granulite facies metamorphism of these supracrustal rocks occurred in the Early–Middle Triassic. Based on the presence of HP granulite facies pelitic rocks, it is inferred that significant underthrusting was involved during the Indosinian Orogeny which introduced these supracrustal rocks to lower crustal levels. [ABSTRACT FROM AUTHOR]

New localities of granulite in the Bamble lithotectonic domain of south Norway illustrate localized distribution of granulite facies rocks in an amphibolite facies gneiss terrain. U–Pb zircon SIMS data constrain the magmatic age of the protoliths to be both 1545 ± 7 to 1542 ± 5 Ma and 1149 ± 8 Ma. They provide a robust date of 1139 ± 11 Ma for metamorphic zircon, supporting available estimates for early-Sveconorwegian metamorphism in Bamble. P–T modeling using Grt + Opx ± Cpx + Pl + Bt + Qz-assemblages yields pressures up to 1.15 GPa and T > 850°C. Clinopyroxene-free granulite assemblages are preserved in low-strain lenses, while high-strain granulite shows crystallization of clinopyroxene. The replacement of orthopyroxene by amphibole illustrates hydration and reequilibration at amphibolite facies. The new findings in Bamble show that granulite-facies rocks occur unevenly distributed in high-grade metamorphic terrains and that relationship between granulite and amphibolite facies is complex and irregular. It suggests that factors as fluid availability, deformation and whole-rock composition are important for metamorphic evolution in addition to pressure and temperature gradients. [ABSTRACT FROM AUTHOR]

• Two-stage clock wise P-T evolution of UHT sapphirine granulites in Madurai block. • U-Pb zircon-monazite-rutile-apatite geochronology record heating/cooling episodes. • Evidence for long-lived Neoproterozoic UHT orogeny and subsequent slow cooling. • Identification of Kambam UHT belt as an important tectonic boundary within SGT. The Precambrian granulite terrane of south India is known for the preservation of regional-scale high to ultrahigh-temperature (HT-UHT) metamorphic rocks. In the Madurai block, the largest crustal block in the terrane, a significant proportion of these HT-UHT rocks occur along a narrow belt referred to as the Kambam ultrahigh-temperature belt. Understanding the P-T-t evolution of these HT-UHT granulites is vital in decoding the spatial and temporal evolution of the Madurai block in relation to other crustal blocks. Here we present the petrology, mineral chemistry, phase equilibrium modelling, and accessory mineral (zircon, monazite, rutile and apatite) geochronological and geochemical data for a hitherto unreported sapphirine granulite from the Kambam ultrahigh-temperature belt. Combined mineral reaction and phase equilibrium modelling indicate extreme P-T conditions up to 1130 °C at 11 kbar. The geometry of the P-T path is clockwise with initial isothermal decompression followed by near isobaric cooling. LA-ICPMS U-Pb geochronological studies on accessory phases report two distinct thermal events: (i) Paleoproterozoic high-T event and associated crustal anatexis at ∼2.5 Ga from zircons and (ii) Neoproterozoic UHT event at ∼550 Ma from monazites. The monazite ages suggest a 50–60 Ma prolonged thermal event, attributed to Ediacaran-Cambrian collisional orogenesis. Additional metamorphic pulses are also identified, demonstrating the polydeformed crustal evolution history of the terrane. U-Pb age dating of rutile and apatite in the sample provide ages of ∼458 Ma and ∼392 Ma and cooling rates of ∼6 °C/Ma and ∼0.3–2 °C/Ma respectively. This suggests a complex history of slow cooling followed by ultraslow cooling. The results bring forth the significance of the Kambam ultrahigh-temperature belt in understanding the tectonothermal evolution of Madurai block and provide additional evidence for long-lived Neoproterozoic UHT orogenesis in south India. [ABSTRACT FROM AUTHOR]

[Display omitted] • UHT granulite rocks were identified in the Madurai block, Lingappanayakannur area, South India. • These metamorphic rocks have undergone a decompressional event. • P-T pseudosections based on the NCKFMASHTO system are indicative of UHT metamorphism. • The UHT metamorphism was caused by the continent-continent collision. Madurai block in South India stands as an excellent example of ultrahigh temperature metamorphic terranes being studied globally to understand the extreme thermal capacities of crustal rocks and the processes that cause these extreme thermal environments. The granulites of the Madurai block were subjected to extreme crustal metamorphism during the Late Neoproterozoic, as evidenced by the texture of the sapphirine + quartz association registered as peak metamorphic assemblage. The metamorphic zircon from sapphirine-granulites produces a U-Pb age of 546.5 ± 7.8 Ma which is interpreted as a global Pan-African crustal evolution event and the dominant zircon population indicates multiple sources of Neoarchean to Paleoproterozoic age in the southern Madurai block. Decompression textures other than orthopyroxene-cordierite ± sapphirine symplectites are indicative of retrograde / exhumation in the granulites metamorphic cycle. P–T pseudosections have been constructed for sapphirine-granulites in relation to the NCKFMASHTO system (Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 –SiO 2 -H 2 O-TiO 2 -O 2) using Perple_X software (version 6). The limitations in the interpretation of mineral reactions and the metamorphic history provided by pseudosection modelling for mineral proportions suggest that the peak metamorphic temperature is ~960 °C and pressure is ~9.2 kbar. [ABSTRACT FROM AUTHOR]