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Potassium (K)-rich mafic rocks are viewed as being derived from partial melting of an enriched mantle source, but it is controversial about which processes cause the mantle enrichment. The Fushui intrusive complex is the largest early Paleozoic K-rich intrusive complex in the eastern Qinling orogen. Therefore, detailed studies on the Fushui complex can contribute not only to understanding of the petrogenesis of K-rich mafic rocks, but also to unraveling the Paleozoic evolution of the Qinling orogen. In this study, we provide an integrated investigation of in situ zircon U–Pb dating and Hf–O isotopes, in combination with whole-rock major and trace elements, as well as Sr–Nd–Hf isotopes, for the Fushui intrusive complex. In situ zircon secondary ion mass spectrometry (SIMS) / laser ablation induction coupled plasma mass spectrometry (LA-ICPMS) U–Pb dating reveals that different rock types of the Fushui complex have identical formation ages of 488–484 Ma. The Fushui complex belongs to the shoshonitic series, and is characterized by extreme large ion lithophile element (LILE, e.g., Ba, U, Th and Sr) and Pb enrichment and depletion of high field-strength elements (HFSEs, e.g. Nb, Ta, Zr, Hf, P and Ti). It shows high initial Sr isotopic ratios (0.7100–0.7151), negative whole-rock e Nd(t) (−3.97 to −5.68) and negative to slight positive whole-rock (−2.24 to 2.38) and zircon (−2.85 to 0.34) e Hf(t) values, as well as high zircon δ18O values (6.86 ± 0.13 ‰). The Hf–Nd isotopic systems are decoupled with positive Δe Hf values (3.85–5.37). These geochemical features indicate that the mantle source has incorporated subducted zircon–barren oceanic sediments. A simple two-end-members mixing model constrains the amount of subducted sediments in the Fushui mantle source to 5–8 %. The Fushui complex originated from 1 to 6 % equilibrium melting of a phlogopite-bearing garnet lherzolite by non-modal melting. As shoshonitic magmas have been discovered in modern nascent arcs, we suggest that the generation of the Fushui complex was induced by the subduction of the Paleotethyan Ocean, when it jumped from the northern to the southern boundary of the North Qinling microcontinent.

To investigate the molecular chaperone function of trigger factor (TF) and its relationship with isomerase activity in vivo, the assisted folding of adenylate kinase (AK) by TF in Escherichia coli was examined by measuring the amounts of soluble AK produced during co-expression. When the mutant of chicken AK, P17G, is expressed in plasmid pBVAK, 95% of the protein is found in inclusion bodies. Co-expression of AK with TF was achieved using a plasmid pBVAT that allowed expression of TF and AK in the same plasmid under separate control. Co-expression with TF resulted in an increase in the amount of soluble AK, with a higher increase when TF was expressed at higher levels in the cell. Co-expression of AK with the two TF mutants, Y221G and F233Y, in which peptidyl-prolyl cis/trans isomerase activity was 1% of wild-type, gave the same results as wild-type TF. This provides in vivo evidence that the molecular chaperone activity of TF is distinct from its isomerase activity.