Abstract:

The petrogenicmetallogenic events developed in Jiawula PbZnAg deposit and their relationships have been highly controversial. This paper reports the SHRIMP zircon U Pb geochronology of the Jiawula oreforming quartzporphyry(JQP) and the late metallogenic dioriticporphyrite(JDP), and their geochemical characteristics. JQP was formed at about 129±4.8 Ma and JDP at about 124±2.5 Ma. Therefore, it is reseanable to consider that the Jiawula Pb Zn Ag mineralization should be occurred during 129124 Ma, i.e. the end of Early Cretaceous. The JQP rocks show high Si, K and low Ca, and belong to subalkaline series in the TAS diagram, to CA series in the diagram of SiO2TFeO/MgO, and to high potassium calc alkalic series in the diagram of SiO2 K2O, enriched in LILE, depleted in HFSE, and having low Sr and high Yb concentrations. The JQP rocks show high Si, K and low Ca, and belong to subalkaline series in the TAS diagram and to TH series in the diagram of SiO2 TFeO/MgO, enriched in LILE, depleted in HFSE, and having low Sr and high Yb concentrations. The geochemical characteristics indicate that the JQP rocks are formed in continental volcanic arc setting with magma derived from crustal melting and the JDP rocks are formed in active continental margin arc setting with magma derived from mantle melting. So this paper suggests that the JQP, JDP magmatism and Pb Zn Ag mineralization in Jiawula all are the products of transformation of MongoliaOkhotsk Ocean from subduction to continenl continent collision at Early Cretaceous time. The Pb Zn Ag deposit in Jiawula should be formed by the post supereruption metallogenesis.

Key words: Jiawula Pb Zn Ag deposit, quartz porphyry, dioritic porphyrite, geochronology, post supereruption metallogenesis