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Although lawsonite eclogite is predicted to be common at depth of ~ 45–300 km in subduction zones, it is rarely exposed at Earth's surface. In this study, we identified a lawsonite (pseudomorph)-bearing eclogite in Yuka terrane, North Qaidam UHPM belt. It is mainly composed of garnet, amphibole, clinozoisite, quartz and rutile with minor omphacite relics and talc. Petrographic investigation identified abundant rectangular- or rhombic- shaped mineral aggregates composed of polycrystalline clinozoisite or polyphase clinozoisite + paragonite ± phengite ± quartz and clinozoisite + amphibole ± quartz ± Na-rich plagioclase occurring in garnet porphyroblasts. The peculiar shape, mineral assemblages and reconstructed compositions of these aggregates show that they are pseudomorphs after lawsonite. Phase equilibrium modeling predicts that the lawsonite (pseudomorph)-bearing eclogite experienced a clockwise P–T evolution with a peak stage at 570 °C, 27 kbar, near the quartz–coesite transition boundary. Geochemical data show that the lawsonite (pseudomorph)-bearing eclogite has a MORB-like affinity with flat Chondrite–normalized rare earth element (REE) distribution patterns. Zircons from this sample have similar δ 18 O values (5.38 ± 0.10‰) with the normal mantle (5.3 ± 0.3‰), indicating that the protolith of the lawsonite (pseudomorph)-bearing eclogite is derived directly from mantle rock without continental crust contamination. The MORB-like character and zircon O isotopic composition of the lawsonite (pseudomorph)-bearing eclogite indicate that its protolith is likely to be an oceanic crustal slice. SIMS and LA–ICP–MS zircon U–Pb dating yielded a 436–438 Ma eclogite-facies metamorphic age for the lawsonite (pseudomorph)-bearing eclogite, similar to the continental subduction age of the North Qaidam UHPM belt, but did not obtain its protolith age. These data indicate that the protolith of the lawsonite (pseudomorph)-bearing eclogite may be either a piece of Proterozoic ocean that was emplaced in the active continental margin of the Qaidam block during the amalgamation of the Rodinia supercontinent, or the early Paleozoic oceanic crust in the transition zone between the Qilian Ocean and the Qaidam block. [ABSTRACT FROM AUTHOR]

• A clockwise P–T path was established for Chachahe eclogites in North Qaidam UHP belt, NW China. • The Chachahe eclogites experienced a 1.92 Ga metamorphic event prior to eclogitization at ∼ 450 Ma. • Overriding plate material can enter subduction channel via tectonic erosion and be carried to mantle depths of ≥ 85 km. Although numerical modelling and marine seismic data show that overriding plate material can enter subduction channel and even recycle to mantle, and finally contribute to mantle heterogeneity and arc magmas, protoliths of the majority of high pressure (HP) and ultrahigh pressure (UHP) metamorphic rocks on the earth's surface originate from the subducting plate. Whether overriding plate material can enter subduction channel and their fate in subduction channel remain enigmas. The North Qaidam UHP Metamorphic Belt (NQUB), located in northwestern China, was formed by north-dipping subduction of the Qaidam Block beneath the Quanji block in the Early Paleozoic. In this paper, we report that some eclogites in Chachahe area, NQUB experienced a 1.92 Ga low-grade metamorphism prior to eclogitization at ∼ 450 Ma. This Paleoproterozoic metamorphic event is not reported in the subducted Qaidam Block but widespread in the overriding Quanji Block, indicating that protoliths of Chachahe eclogites originated from the overriding plate. A clockwise P–T path from 12 kbar/520 °C to near UHP conditions of 25.5 kbar/690 °C, followed by isothermal decompression, was estimated for the Early Paleozoic metamorphism using a combination of garnet major and trace element zoning, phase equilibrium modelling and thermobarometry. This P–T path pattern is similar to other eclogites in this area, protoliths of which originated from the subducted plate. These results clearly show that overriding plate material can enter subduction channel and be carried to mantle depths of at least 85 km and exhume fast along subduction channel with other slices from subducted slab. [ABSTRACT FROM AUTHOR]

The lack of long-term air-stable and solution-processed n-doping methods for printed single-walled carbon nanotube (SWCNT) thin film transistors (TFTs) limits their integrations into printed complementary metal-oxide-semiconductor (CMOS) circuits. In this paper, a new chemically modified epoxy amine ink was developed as the chemical dopant and encapsulant to enable the uniform n-type SWCNT-TFTs with long-term air stability (6 months). The epoxy amine inks were dropped onto the printed p-type TFT device channels in a single-step solution process. As a result, printed top-contact n-type SWCNT-TFTs were obtained with well-balanced electrical chararcteristics comparable to their p-type counterparts. The matched p-type and n-type SWCNT-TFTs were thus integrated into the printed CMOS inverters and NAND gates, which have both achieved proper logic operation at supply voltages below 1 V. In particular, the CMOS inverters could operate with V DD down to 0.3V with associated peak power consumption of 0.06 μW, showing full rail-to-rail output swings with voltage gains up to 22, trip voltages of ∼V DD /2, and maximum noise margin of 0.42 V at V DD = 1.1 V (∼76.4% of V DD /2). Furthermore, the static characteristics of CMOS inverters could be maintained for 3 months with negligible changes, proving the feasibility of this long-term air-stable n-doping method. A novel epoxy-amine ink was developed as the chemical dopant and encapsulant to enable the uniform and long-term air-stable n-type SWCNT-TFTs, which showed well-balanced electrical properties comparable to their p-type counterparts. These matched p-type and n-type SWCNT-TFTs could be intergrated into the high air-stable and good-performance printed CMOS inverters and NAND gates. The CMOS inverters could operate with V DD down to 0.3 V with associated peak power consumption of 0.06 μW, showing full rail-to-rail output swings with voltage gains up to 22, trip voltages of ∼V DD /2, and maximum noise margin of 0.42 V at V DD = 1.1 V (∼76.4% of V DD /2). In addition, the NAND gates can work well without any voltage loss at input voltages of 1 V. Image 1 [ABSTRACT FROM AUTHOR]