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Numerous lenses of eclogite occur in a belt of augen orthogneisses in the Gubaoquan area in the southern Beishan orogen, an eastern extension of the Tianshan orogen. With detailed petrological data and phase relations, modelled in the system NCFMASHTO with THERMOCALC THERMOCALC, a quantitative P-T path was estimated and defined a clockwise P-T path that showed a near isothermal decompression from eclogite facies (>15.5 kbar, 700-800°C, omphacite + garnet) to high-pressure granulite facies (12-14 kbar, 700-750°C, clinopyroxene + sodic plagioclase symplectitic intergrowths around omphacite), low-pressure granulite facies (8-9.5 kbar, 700°C, orthopyroxene + clinopyroxene + plagioclase symplectites and coronas surrounding garnet) and amphibolite facies (5-7 kbar, 600-700°C, hornblende + plagioclase symplectites). The major and trace elements and Sm-Nd isotopic data suggest that most of the Beishan eclogite samples had a protolith of oceanic crust with geochemical characteristics of an enriched or normal mid-ocean ridge basalt. The U-Pb dating of the Beishan eclogites indicates an Ordovician age of c. 467 Ma for the eclogite facies metamorphism. An 39 Ar ⁄ 40 Ar age of c. 430 Ma for biotite from the augen gneiss corresponds to the time of retrograde metamorphism. The combined data from geological setting, bulk composition, clockwise P-T path and geochronology support a model in which the Beishan eclogites started as oceanic crust in the Palaeoasian Ocean, which was subducted to eclogite depths in the Ordovician and exhumed in the Silurian. The eclogite-bearing gneiss belt marks the position of a high-pressure Ordovician suture zone, and the calculated clockwise P-T path defines the progression from subduction to exhumation.

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The Xiadong mafic-ultramafic complex lies in the central part of the Middle Tianshan Massif (MTM), along the southern margin of the Central Asian Orogenic Belt (CAOB). This complex is composed of dunite, hornblende (Hbl) clinopyroxenite, hornblendite, and Hbl gabbro. These rocks are characterized by adcumulated textures and variable alteration. Orthopyroxene is an extremely rare mineral in all rock units and plagioclase is absent in dunite and Hbl clinopyroxenite. Hbl, Fe-chromite, and Cr-magnetite are common phases. Olivines have forsterite (Fo) contents ranging from 92.3 to 96.6. Clinopyroxenes are Ca-rich, Ti-poor diopsides, and mostly altered to tremolites or actinolites. Chromites display low TiO 2 and Al 2 O 3 contents and high Cr# and Fe 2+ /(Fe 2+ + Mg) values. Primary and secondary Hbls show wide compositional variations. These petrological and mineralogical features as well as mineral chemistry are comparable to typical Alaskan-type complexes worldwide, which are widely considered to have formed above subduction zones. The chemistry of clinopyroxene and chromite supports an arc plate-tectonic origin for the Xiadong complex. Its confirmation as an Alaskan-type complex implies that the MTM, with Precambrian basement, was probably a continental arc during oceanic plate underflow and further supports the hypothesis of southward subduction of the Palaeozoic Junggar Ocean.

Over 1400 electron probe and 700 ion probe microanalyses were performed on eleven mineral separates to evaluate their potential as reference materials for in situ Li isotopic determination. Our results suggest the homogenous distributions of major elements, Li and its isotopes for each sample. Hence, these samples are suitable to be used as reference materials for in situ measurements of Li abundance and Li isotopes by secondary ion mass spectrometry (SIMS) or laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). These samples have the advantage of mitigating probable matrix effects during calibration owing to the wide range of compositions. The effect of composition on the δ7Li of olivine measured by SIMS is a linear function of composition, with δ7Li increasing by 1.0‰ for each mole per cent decrease in forsterite component.

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