Zircon U-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon U-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of U-Pb age. Three methods have been proposed to link zircon U-Pb age to metamorphic conditions: (i) internal structure; (ii) trace element feature; (iii) mineral inclusion composition. Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances, with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks. Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore, interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.

Genesis of zircon and its constraints on interpretation of U-Pb age

https://www.geol.umd.edu/~rudnick/PDF/Gao_2003_EPSL.pdf

Re-Os evidence for replacement of ancient mantle lithosphere beneath the North China Craton

Stable isotope geochemistry of ultrahigh pressure metamorphic rocks from the Dabie–Sulu orogen in China: implications for geodynamics and fluid regime

Tectonic evolution of a composite collision orogen: An overview on the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt in central China

Determining the depth to which continental lithosphere can be subducted into the mantle at convergent plate boundaries is of importance for understanding the long-term growth of supercontinents as well as the dynamic processes that shape such margins. Recent discoveries of coesite and diamond in regional ultrahigh-pressure (UHP) metamorphic rocks has demonstrated that continental material can be subducted to depths of at least 120 km (ref. 1), and subduction to depths of 150-300 km has been inferred from garnet peridotites in orogenic UHP belts based on several indirect observations. But continental subduction to such depths is difficult to trace directly in natural UHP metamorphic crustal rocks by conventional mineralogical and petrological methods because of extensive late-stage recrystallization and the lack of a suitable pressure indicator. It has been predicted from experimental work, however, that solid-state dissolution of pyroxene should occur in garnet at depths greater than 150 km (refs 6-8). Here we report the observation of high concentrations of clinopyroxene, rutile and apatite exsolutions in garnet within eclogites from Yangkou in the Sulu UHP metamorphic belt, China. We interpret these data as resulting from the high-pressure formation of pyroxene solid solutions in subducted continental material. Appropriate conditions for the Na2O concentrations and octahedral silicon observed in these samples are met at depths greater than 200 km.

The possible subduction of continental material to depths greater than 200 km

Large areal extent of ultrahigh-pressure metamorphism in the Sulu ultrahigh-pressure terrane of East China: new implications from coesite and omphacite inclusions in zircon of granitic gneiss

Mineral inclusions in zircon from gneisses in the ultrahigh‐pressure (UHP) zone of the Dabie Mountains, China, are studied by using laser Raman spectrophotometry. We identified numerous mineral inclusions including coesite, quartz, clinopyroxene, phengite, barite, anhydrite, and feldspar. Coesite is found to occur as zircon‐hosted inclusions in all types of gneisses, indicating that these gneisses had shared the ultrahigh‐pressure metamorphic history with the UHP eclogite blocks that reside in them. The occurrence of barite and anhydrite probably implies the existence of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontC...

https://www.jstor.org/stable/10.1086/320796

Mineral Inclusions in Zircon from Gneisses in the Ultrahigh‐Pressure Zone of the Dabie Mountains, China

Sm–Nd geochronology and petrography of garnet pyroxene granulites in the northern Sulu region of China and their geotectonic implication

A transitional eclogite- to high pressure granulite-facies overprint on coesite eclogite at Taohang in the Sulu ultrahigh-pressure terrane, Eastern China

Seismic tomography is used to determine three-dimensional velocity structure of the Dabie-Sulu orogen in eastern China. The high resolution image of the P-waves velocity structure is obtained for the uppermost mantle to a depth of at least 150 km, along the latitudes of 30°–38°N and longitudes of 114°–122°E. Results of this inversion reveal a slab-like high velocity anomaly under this orogen in the depth from Moho discontinuity to at least 110 km. It may represent a remnant of the subducted Yangtze block during the period of Triassic continent-continent collision.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000GL012187

Bolin Cong

Papers

Large areal extent of ultrahigh-pressure metamorphism in the Sulu ultrahigh-pressure terrane of East China: new implications from coesite and omphacite inclusions in zircon of granitic gneiss

Mineral Inclusions in Zircon from Gneisses in the Ultrahigh‐Pressure Zone of the Dabie Mountains, China

Sm–Nd geochronology and petrography of garnet pyroxene granulites in the northern Sulu region of China and their geotectonic implication

A transitional eclogite- to high pressure granulite-facies overprint on coesite eclogite at Taohang in the Sulu ultrahigh-pressure terrane, Eastern China

Slab‐like high velocity anomaly in the uppermost mantle beneath the Dabie‐Sulu Orogen