Abstract
The Duobaoshan Cu (Mo) deposit is one of the oldest super large porphyry deposits in the eastern part of the Central Asian orogenic belt. Although ore-forming processes have been extensively concerned, the post-mineralization ore preservation state was poorly focused on. In order to improve the ability of prospecting forecast, it is necessary to consider both deposit formation and deposit preservation. Here, we reported apatite fission track (AFT) data for the Duobaoshan porphyry copper deposits in the belt to reveal the cooling and exhumation history and evaluate ore preservation. The results show that the rapid cooling of the ore-hosting rock body occurred later than the surrounding rock body. The rapid cooling of the surrounding granodiorite occurred between 82 and 72 Ma, with the exhumation depth of 2.33–3.11 km and the exhumation rate of 0.25 mm/a, whereas the ore-hosting granodiorite porphyry was rapid cooling between 71.8 and 50.2 Ma, with the exhumation depth of 2.99–3.86 km and the exhumation rate of 0.22 mm/a. This differential exhumation and cooling event provide favorable geological conditions for the preservation of the ore body.
Highlights
Porphyry Cu (Mo) deposits are distributed in rocks formed in different periods from the Archean to the present, but mainly formed in the Meso–Cenozoic, and are spatially concentrated in three tectonic metallogenic regions: the Pacific belt, the Tethys region and the Central Asian–Mongolian– Hinggan region
The apatite fission track (AFT) ages of the six samples range between 50.2 ± 3.0 and 76.0 ± 3.8 Model Age (Ma)
Samples DB01 and DB120 were collected from the surrounding rock and yielded AFT ages of 71.8 ± 3.5 Ma and 76.0 ± 3.8 Ma, respectively
Summary
Porphyry Cu (Mo) deposits are distributed in rocks formed in different periods from the Archean to the present, but mainly formed in the Meso–Cenozoic, and are spatially concentrated in three tectonic metallogenic regions: the Pacific belt, the Tethys region and the Central Asian–Mongolian– Hinggan region. More than half of the 25 largest known porphyry copper deposits, formed during three periods: the Paleocene–Eocene, Eocene–Oligocene, and middle Miocene–Pliocene [1]. The Miocene porphyry copper deposits such as the Zhunuo deposit in the Gangdese belt of southern Tibet, the post-mineralization granite porphyry yielded a zircon U-Pb age of 12.0 ± 0.2 Ma and molybdenite Re-Os isotopic data indicate mineralization likely occurred from 14.8 ± 0.1 Ma to 13.5 ± 0.1 Ma [2]. Most porphyry deposits formed before the Mesozoic have been destroyed or even exhumated completely. The porphyry Cu (Mo) deposits that formed before the Mesozoic are mainly located in the Central Asian– Mongolian–Hinggan Paleozoic Orogenic Belt, and the Duobaoshan porphyry Cu (Mo) deposit is one such deposit. The Duobaoshan deposit is a classic porphyry Cu (Mo) deposit that formed in an early
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