Ore-controlling structures of the Qingchengzi Pb-Zn-Au-Ag orefield, northeastern China and significance for deep ore prospecting: Revealed from gravity and magnetic anomalies

Abstract

Located in the middle of Liaodong Rift, the Qingchengzi orefield is an important Pb-Zn-Ag-Au polymetallic mining area in Northeast China. The Pb-Zn-Au-Ag mineralization mainly occurs in the Liaohe Group strata and is closely related to Indosinian and Yanshanian magmatic intrusive bodies. Currently the Qingchengzi orefield is poorly explored at depths greater than 1500 m, with no large deep concealed gold deposit being discovered yet. This study focused on delineating deep concealed ore-controlling structures from the local gravity and aeromagnetic anomalies in different wavelet orders acquired by the application of discrete wavelet transform (DWT), and evaluating their potential for undiscovered gold-rich polymetallic mineralization in the Qingchengzi orefield. We started from summarizing the characteristics of gravity and magnetic anomalies corresponding to the ore-controlling structures obtained from surface geology, exploration profiles and drilling results. Under the guidance of the correspondence, we interpreted the structural control factors of the tectonic-magmatic metallogenic system for the whole Qingchengzi orefield, such as faults, strata, magmatic bodies and mineralized alteration belts. Based on the spatial relationship between the known deposits and structural factors interpreted from gravity and magnetic anomalies, it is concluded that the gold-rich polymetallic deposits and mineralization are controlled by five major deep regional faults (two in the NE direction and three in the NW direction). Moreover, the borders of the Indosinian and Yanshanian concealed magmatic intrusions, as well as the intersections of deep regional faults are more favorable for the deposition of gold-rich polymetallic minerals. A NNE-trending concealed structure was found in the middle of our study area, connecting the Shuangdinggou, Qingchengzi, Xinling and Gujiagou intrusions, serving as a possible channel for magmatic activities in the Indosinian. The forward modeling results on the gravity and magnetic data of profile L1 indicates that the Liaohe Group strata and the possible Mesozoic concealed intrusion lies beneath the Paleoproterozoic Dadingzi granite. This finding supplements the traditional understanding that the Paleoproterozoic Dadingzi granite is the deepest boundary for ore prospecting, and provides new thoughts searching for deep-seated ore bodies for the Xiaotongjiapuzi ore deposits.