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• The Lawu volcanic rocks and associated porphyries have a closely comagmatic relation. • The mantle domains were metasomatized by Paleo-Tethyan oceanic marine sediments. • The porphyry-volcanic system has similar H 2 O but lower fO 2 of than Yulong deposit. Generally, porphyry Cu deposits are associated with the comagmatic porphyry (or subvolcanic)-volcanic systems of high magmatic H 2 O-fO 2 conditions. The volcanic rocks, as the counterpart of the porphyries, thus can provide some significant insights into the fertility of the porphyries to some extent. For this reason, we have used the Lawu volcanic rocks and spatial-temporal closely-related porphyries in the newly discovered porphyry Cu prospects (e.g., Seli, Zongguo, Mamupu) in the southern segment of the Yulong intracontinental porphyry Cu belt to illustrate the relationship between the porphyries and volcanic rocks, petrogenesis of the volcanic rocks, and then to evaluate the ore potential of the porphyries based on the magmatic H 2 O-fO 2 conditions. Both the Lawu volcanic rocks and Seli-Zonguo-Mamupu porphyries are shoshonitic and metaluminous, and have similar REE patterns, and Sr-Nd-Hf isotopic compositions, which suggest a comagmatic relation between the volcanic rocks and porphyries. An episodic magmatism model is proposed to explain the slightly younger age (~36–35 Ma) and less evolved nature of volcanic rocks than the porphyries. The Lawu volcanic rocks of mainly intermediate composition (SiO 2 = 54.25–64.68 wt%) have high K 2 O (4.75–5.94 wt%) and high K 2 O/Na 2 O ratios (1.69–2.00), broadly similar to the coeval Yulong fertile granitic porphyries and the Nangqian mafic lavas. The (87Sr/86Sr) i and ε Nd (t) values, uniform zircon ε Hf (t) and δ18O values, and lack of inherited zircons of the Lawu volcanic rocks don't support their formation by mixing between the mantle-derived Nangqian mafic lavas and crust-derived Yulong felsic porphyries or assimilation and fractional crystallization (AFC) of mafic magmas. They are characterized by high Ba/Th, Ba/La and listric-shaped normalized rare earth element profile with significantly negative Nb-Ta-Ti anomalies, and have high initial 87Sr/86Sr ratios (0.7071–0.7079) and low ε Nd (t) values (−5.71 to −3.05), and low zircon ε Hf (t) (−1.53 to 4.09) and clearly high δ18O values (6.67–8.42‰), suggesting that, they were probably formed by fractional crystallization (FC) of mantle-derived mafic magmas and originated from mantle domains modified by significant amount of H 2 O-rich marine sediments of the Paleo-Tethyan oceanic slab. Magmatic H 2 O contents calculated from deepest-crystallized amphiboles indicate that, the Lawu volcanic rocks and Zongguo porphyries have initial magmatic H 2 O contents as high as the Yulong fertile porphyries and typical porphyry Cu systems worldwide (commonly >4 wt% H 2 O). Magmatic fO 2 (ΔFMQ) of the Lawu volcanic rocks (0.6–1.3, ave. 0.9 ± 0.1) and the Zongguo porphyries (0.9–1.7, ave. 1.4 ± 0.2) are clearly lower than the fertile porphyries in the giant Yulong deposit (ΔFMQ = 1.6–3.3, ave. 2.3 ± 0.5) and typical porphyry Cu deposits in the world (commonly ΔFMQ > 2). The slightly lower magmatic H 2 O contents and slightly higher magmatic fO 2 of the Zongguo porphyries than the Lawu volcanic rocks were ascribed to variable degassing during magmatic evolution. These suggest that, in spite of the high magmatic H 2 O contents, the comagmatic porphyries (at least the Zongguo porphyries) of the Lawu volcanic rocks in the southern segment of the Yulong porphyry Cu belt are unlikely to produce large-scale porphyry Cu mineralization like the giant Yulong deposit, due to the low magmatic fO 2 conditions. [ABSTRACT FROM AUTHOR]

The giant sediment-hosted Jinding zinc-lead deposit is located in the Lanping Basin, northwestern Yunnan Province, China. The genesis of the deposit has long been debated and the sources of the ore-forming fluids and metals are controversial. This study presents rare earth element (REE) and noble gas isotope data that constrain the origins of the ore fluids and the heat source driving the hydrothermal circulation. The early-stage sulfides are enriched in light REEs and have high ∑REE values (30.8–94.8 ppm) and weakly negative Eu (δEu 0.85–0.89) and Ce anomalies (δCe 0.84–0.95), suggesting that the fluids were likely derived from dissolution of Upper Triassic marine carbonates with input of REEs from aluminosilicate rocks in the basin. In contrast, the late-stage sulfides have irregular REE patterns, generally low ∑REE values (0.24–10.8 ppm) and positive Eu (δEu 1.22–10.9) and weakly negative Ce anomalies (δCe 0.53–0.90), which suggest that the ore-forming fluids interacted with evaporite minerals. The 3 He/ 4 He (0.01–0.04 R a ) and 40 Ar/ 36 Ar values (301–340) of the ore-forming fluids indicate crustal and atmospheric origins for these noble gases. These findings are in agreement with the published fluid inclusion microthermometry data and the results of H, O, C, S, Pb and Sr isotope studies. Our data, in combination with published results, support a two-stage hydrothermal mineralization model, involving early-stage basinal brines and late-stage meteoric water that acquired metals and heat from crustal sources. [ABSTRACT FROM AUTHOR]

• High-Mg volcanic rocks in the Nangqian basin are slightly older than the counterparts from the Dali district. • Underneath the Nangqian basin is a juvenile, isotopically "depleted" garnet-dominant SCLM. • The SCLM was metasomatized by Palaeozoic oceanic slab subduction and Cenozoic continental subduction. • The SCLM underneath Dali was only metasomatized by the Neoproterozoic oceanic subduction. • Different compositions of high-Mg volcanic rocks from Nangqian and Dali were due to heterogeneous mantle sources. Cenozoic (∼40–30 Ma) high-Mg potassic volcanic rocks are abundant in the Jinshajiang–Ailaoshan magmatic belt that stretches from eastern Tibet to western Yunnan. The petrogenesis and compositional variation of the mantle source of these rocks are poorly known. In this paper, we obtained U-Pb zircon ages and whole-rock major and trace element and Sr-Nd-Pb-Hf isotopic data for these volcanic rocks from the Nangqian basin in the Eastern Qiangtang block, eastern Tibet. High-Mg volcanic rocks in Nangqian are potassic trachybasalts, shoshonites and latites and contain 6.49–10.54 wt% MgO, 48.04–56.89 wt% SiO 2 and 3.36–4.14 wt% K 2 O, with K 2 O/Na 2 O ratios of 0.94–1.24. Zircon U-Pb dating shows that they are slightly older (40–38 Ma) than their counterparts (37–32 Ma) from the Dali district, western Yunnan. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and have significantly negative Nb-Ta-Ti anomalies. Isotopically, they have primitive mantle-like 87Sr/86Sr ratios (0.7050–0.7055) and εNd(t) values of −1.06 to +0.10 and restricted ranges of 206Pb/204Pb (18.63–18.71), 207Pb/204Pb (15.52–15.57) and 208Pb/204Pb ratios (38.42–38.59). Zircon εHf(t) values vary from +4.1 to +9.4 and are thus decoupled from their whole-rock Nd isotope ratios. Previous studies have shown that Cenozoic high-Mg potassic volcanic rocks in the Dali district have more enriched Sr-Nd-Pb-Hf isotopic compositions, higher LILE/HFSE (high field strength elements) and LILE/LREE ratios but less enrichment in LREE than the counterparts from the Nangqian basin. Geochemical differences between high-Mg volcanic rocks from these two locations can be explained by different mantle sources caused by different metasomatic processes. Underneath the Nangqian basin, a juvenile, isotopically "depleted", and garnet-bearing lithospheric mantle was metasomatized by Paleozoic and Cenozoic subduction, whereas an ancient (probably as old as Neoproterozoic), fertilized, and spinel facies-dominated lithospheric mantle was metasomatized by Neoproterozoic subduction underneath the Dali district. [ABSTRACT FROM AUTHOR]