Genesis of the stratiform Zhenzigou PbZn deposit in the North China Craton: RbSr and COSPb isotope constraints

Zhenzigou PbZn deposit is a typical deposit as its development of stratiform PbZn ore body, along with the veined ore body. Because of its complicated mineralization process, a great deal of debate exists about its main metallogenic epoch, ore-forming material source and metallogenic mechanism. After intensive study, this paper obtains bullet points as follows:•This study got the RbSr isochron age of sphalerite(1798 ± 8 Ma) from stratiform PbZn ore body for the first time. We consider that this age represents the ending age for the stratiform PbZn ores of Zhenzigou deposit;•This study explained the source of ore-forming materials about stratiform PbZn ore body, veined PbZn ore body, wallrocks and related magmatite in Zhenzigou deposit based on comprehensive analysis about C-O-S-Pb isotope data;•This study proposed a genetic model for the deposit: a. Rift and depression stage; b. Sedimentary mineralization period; c. Metamorphic transformed period; d: Triassic alkaline magmatism period resulted in second epigenetic (remobilized) mineralization and the veined ores formed in this stage.

Isotopes (RbSr, C, O, S, and Pb) were investigated from the Zhenzigou PbZn deposit in the Qingchengzi mineral field (QMF) of the North China Craton as an aid to determine the genesis of stratiform PbZn deposits in the Liao-Ji Rift. A step-dissolution RbSr age of 1798 ± 8 Ma with 206Pb/204Pb ratios of 17.7477–17.8527 were obtained from sphalerite. Sulfur isotopic ratios for pyrite (5–14.4‰), sphalerite (2.4–8.6‰), and galena (− 0.3–8.6‰) from Zhenzigou have a narrower range than those from the host Paleoproterozoic Dashiqiao Formation, and granite in the area. Calcite and limestone from ore and wallrocks at the deposit have similar C and O isotope compositions, with δ13CPDB ranging from − 6.0 to − 2.3‰ and δ18OSMOW from 9.8 to 13.7‰, which are similar to those of carbonatite and the mantle.Comprehensive analysis of the Pb isotopic composition of the sulfide from the Zhenzigou deposit and PbZn deposits in adjacent area show that the Pb originated from the upper crust and mixed with Pb from the mantle. Sulfur isotopes from Zhenzigou deposit indicate that the mineralization has a volcanic eruption source. The δ13CPDB and δ18OSMOW values indicate that the CO2 originated from a mixed mantle, marine carbonate and organic source.Combined with the study of regional metallogenic background, this paper proposes that deposition of stratiform PbZn mineralization in the QMF began ca. 2052 Ma during development of the Liaoji Rift. The mineralization extended to ca. 1798 Ma prior to deformation associated with the Lvliang Movement, which dismembered the stratiform PbZn mineralization. The veined mineralization in the region cross-cuts the stratiform deposits and represents remobilized and redeposited deposits associated with the emplacement of Triassic plutons such as the Xinling and Shuangdinggou granites.

Graphical abstractThe mineralization process of Zhenzigou PbZn deposits can be divided into four stages based on this study: a. Rift and depression stage of ancient continent: the early stage of extensional tectonics was accompanied by mantle upwelling, crustal thinning and large-scale bimodal volcanic activities; b. Sedimentary mineralization period: transgression increased and the lithosphere became more stable at the end of extension in the Liaoji Rift, which was proper for deposition of the Liaohe Group accompanied by volcanism associated various mineral deposits, and the stratiform lead-zinc initially formed (2052–1798 Ma); c. Metamorphic transformed period: an intensive tectonic-magma-metamorphism event by ca 1798 Ma during the “Lvliang Movement” destroyed the syngenetic stratiform PbZn ores; d: Triassic alkaline magmatism (225–140 Ma) resulted in second epigenetic (remobilized) mineralization and the veined ores formed in this stage.Figure optionsDownload full-size imageDownload as PowerPoint slide