The genesis of continental collision-related porphyry Cu deposits (PCDs) remains controversial. The most common hypothesis links their genesis with magmas derived from subduction-modified arc lithosphere. However, it is unclear whether a genetic linkage exists between collision-and subduction-related PCDs. Here, we studied Jurassic subduction-related Cu-Au and Miocene collision-related Cu-Mo porphyry deposits in south Tibet. The Jurassic PCDs occur only in the western segment of the Jurassic arc, which has depleted mantle-like isotopic compositions [e.g., (87 Sr/ 86 Sr) i = 0.7041-0.7048; e Nd(t) as high as 7.5, and e Hf(t) as high as 18]. By contrast, no Jurassic PCDs have been found in the eastern arc segment, which is isotopically less juvenile [e.g., (87 Sr/ 86 Sr) i = 0.7041-0.7063, e Nd(t) < 4.5, and e Hf(t) ≤ 12]. These results imply that incorporation of crustal components during underplating of Jurassic magma induced copper accumulation as sulfides at the base of the eastern Jurassic arc, inhibiting PCD formation at this time. Miocene PCDs are spatially confined to the Jurassic arc, and the giant Miocene PCDs cluster in its eastern segment where no Jurassic PCDs occur. This suggests that the arc segment barren for subduction-related PCDs could be fertile for collision-related PCDs. Miocene ore-forming porphyries have young Hf model ages and Sr-Nd-Hf isotopic compositions overlapping with those of the Jurassic rocks in the eastern segment, whereas contemporaneous barren porphyries outside the Jurassic arc have abundant zircon inheritance and crustlike Sr-Nd-Hf isotopic compositions. These data suggest that remelting of the lower crustal sulfide-bearing Cu-rich Jurassic cumulates, triggered by Cenozoic crustal thickening and/or subsequent slab break-off, led to the formation of giant Miocene PCDs. The spatial overlap and complementary metal endowment between subduction-and collision-related magmas may be used to evaluate the mineral potential for such deposits in other orogenic belts.

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Background: Antiretroviral therapy (ART) demonstrates high efficacy in reducing the risk of HIV transmission to sexual partners. However, it is not clear if the use of pre-exposure prophylaxis (PrEP) in HIV-1-serodiscordant couples is necessary during natural conception when the HIV-positive partner exhibits a suppressed viral load. The purpose of this study was to assess the role of PrEP during natural conception in this population. Methods: A retrospective, multicenter study was conducted in a cohort of HIV-1-serodiscordant couples (positive man, negative woman) with childbearing desires. HIV-positive male partners were treated with ART and achieved viral suppression for more than half a year. The HIV-negative female partners were either treated with PrEP or not treated with PrEP, and outcomes were compared between the two treatment groups. Results: Of 246 HIV-1-serodiscordant couples in whom the HIV-positive partner achieved viral suppression, 104 seronegative women were treated with PrEP during natural conception and 142 seronegative women were not treated with PrEP. There were 410 condom-less sexual acts in couples treated with PrEP and 615 condom-less sexual acts in couples not treated with PrEP. We observed no instances of HIV transmission in HIV-1-serodiscordant couples with or without the use of PrEP during the process of natural conception. Conclusions: Our results show that PrEP had minimal influence in reducing the risk of HIV transmission during natural conception in HIV-1-serodiscordant couples with a stably suppressed viral load. Thus, it may be an acceptable option for HIV-negative partners to not use PrEP during the process of natural conception if the HIV-positive partner has achieved viral suppression for more than half a year.

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