Magnetotelluric Sounding For The Influence Of Subduction Of The Pacific Plate On Mineralization In The Eastern Part Of South China

Influenced by the subduction of the Pacific Plate,the South China Block underwent explosive mineralization in the Mesozoic,and a series of important ore concentration areas and metallogenic belts,such as the Middle-Lower Yangtze River metallogenic belt(MLY)and the Wuyishan metallogenic belt(WMB).Among them,the MLY was formed in the Yanshanian period,and is composed of a series of iron,copper,gold,lead,zinc and Polymetallic deposit metallogenic series.The ore-controlling structure of the MLY is controlled by the Yangtze fault zone and belongs to the mantle uplift zone.Mantle-derived materials play a dominant role in its metallogenic process.The WMB was formed in the Indo-Yanshan period,and consists of a series of series of niobium,tantalum,tin,gold,silver and Polymetallic deposit metallogenic series.The metallogenic tectonic background of the WMB is the structural metamorphic belt in the South China orogenic belt.The ore-forming rocks are related to Indosinian metamorphic granite and Yanshanian granite,and mainly crust-derived materials are involved in diagenesis and mineralization.Therefore,the mineral type of the WMB is crustal,while the mineral type of the MLY is mantle.To study the deep electrical structures and metallogenic types of the MLY and WMB,691 magnetotelluric(MT)stations in the eastern part of South China were employed to obtain a lithospheric 3-D electrical structure model.Combine 3-D electrical structure model with relevant geological and geophysical data to explain it.The electrical structure of the crust in eastern South China is generally characterized by high-resistivity.In the upper mantle part of South China,the eastern Yangtze Block is characterized by low-resistivity anomalies,the Cathaysia Block and the Jiangnan orogenic belt are characterized by high-resistivity,but there is a clear NE-SW-oriented low-resistivity band,which may indicate asthenosphere material Upwell along the weak fracture location.The results show a wide range of low-resistivity anomalies in the upper mantle of the MLY.Moreover,the anomalies bodies have the same trend as the metallogenic belt,which may be the upwelling asthenosphereic materials.The low-resistivity anomaly of the upper mantle of the MLY showed a spatial distribution characteristic that gradually became shallower from south to north,it shows that the hot material in asthenosphere is upwelling from south to north.There may be a corresponding relationship between the time distribution of mineralization activities gradually changing from south to north.According to the 3-D electrical structure model,there are low-resistivity anomalies deep in the WMB,but the scale is relatively small.It is presumed to be the ascending channel of asthenosphere material in the WMB,and the ore-bearing asthenospheric material invaded the lower crust through the migration channel of the fault zone or fault.After the asthenosphere material melts with the material in the lower crust,it intrudes into the upper crust through deep faults and metasomatizes with ore-forming elements to form a new crust.The metallogenic elements in the WMB are mainly crust-derived materials,and a small amount of mantle-derived materials are involved.Eventually,mantle-derived materials in the vicinity of Wuyi Mountain form copper,gold and other polymetallic deposits,while crust-derived materials form tungsten,rare earth and other mineral deposits.The deep metallogenic mechanism and magmatic activity of the MLY and the WMB may be affected by the subduction of the Pacific plate.