Key Ore-controlling Factors of the Skarn Type High-grade Iron Deposits in North China Craton:Constraints from Stratigraphy
The key ore-controlling factors of the skarn high-grade iron deposits in North China Craton(NCC)is a challenging topic and largely restrict the ore-prospecting directions in the future and make relevant study breakthroughs impossible.Based on the distribution pattern of typical orebodies in NCC and stratigraphy,we determined the key ore-controlling factors and their restriction mechanism.The large scale of orebodies of typi-cal skarn high-grade iron deposits in NCC are closely related to the surrounding rock series(e.g.,karst layers,gypsum beds)and they are mainly distributed in the middle Carboniferous Fengfeng Formation,the lower Majia-gou formation,and the upper Majiagou Formation,which are located in the karst stratum above gypsum.The key controlling factors from stratigraphy on the mineralization of skarn type high-grade iron deposits are mainly manifested in four aspects:the vertical distribution of karst stratum restricts the favorable space for the emplace-ment of iron-rich orebodies;the unconformity surface controls the development of the karst system,affecting the scale of high-grade iron orebodies;the sequence stratigraphy affects the karst stages,constraining the distribu-tion of karst layers and high-grade iron orebodies;the gypsum salt layer indicates the bottom boundary of the strongly phased karstification,limiting the favorable lower bound for hosting the high-grade iron orebodies.Consequently,the ore-prospecting model for the skarn type high-grade iron deposits in NCC was established,and seven potential mineralization spatial segments,including three major ones,were recommended in the stud-y.The key ore-prospecting and research directions were suggested at end of the study.
key ore-controlling factorhigh-grade iron depositskarnstratigraphyNorth China Craton