The Metallegenic Regularity Of The Jinqingding Gold Deposit Field And Ore Prospecting, In Rushan, Shandong Province

This study focused on certain problems in urgent need of solving in the Rushan ore field, particularly in the Jinqingding gold deposit, using analyses of the ore fluid geochemistry, and aims to obtain some new findings in the mineral resource occurrence and ore prospecting. The major achievements are summarized as follows:1. On the basis of temporal and spatial analyses in relation to ore deposits or mineralized localities, ore-controlling structures and magmatic intrusions, the emplacement of igneous bodies was believed to have been caused by tectonics, and specifically, the ore-controlling structures were originated from the episodical magmatic intrusion of Mesozoic age. The jointing belt of NS-orientated ore-controlling faults with the marginal structures of Mesozoic granitoids led to gold metallogeny and controlled the plunging attitude of orebodies, which exclusively dips toward the younger intrusion and has no bearing on some normal, reversed and sinistral or dextral strike-slipping faults.2. Some daughter minerals in high-salinity fluid inclusions were discovered in the Jugezhuang intrusion. This fact, combined with the REE characteristics of gold deposits and Mesozoic magmatic rocks and also based on relevant temporal and spatial analyses, suggests that the Jugezhuang and Shitouquan intrusions in the Kunyushan batholith complexes were responsible for gold veining and controlled the occurrence of large to medium size gold deposits.3. The contour map in products of the orebody width multiplied by Au grade for Orebody II of the Jinqinding gold deposit was made in the light of structural and latest exploration data, indicating that the occurrence of the chief reef for Orebody II was primarily connected to attitude changes of the pertinent fault plane. It was distributed in echelon, plunged toward northeast and was shaped by both north- and south-dipping fractures. Quantitative analyses of Au and associated commodities, such as correlation coefficients and spatial distribution, show that two concentration ceters are present in Orebody II.4. Detailed studies of structures in the Jinqingding ore field revealed that gold veins traced both NNE- or NNW-orientated and NE- or NNE-trending fault systems at a deep level, and their down-going development, alternatively, followed two fractures that dip southwards and northwards, respectively. Rich and thick reefs were mostly related to NWW- or SEE-dipping faults, whereas the NEE- or SWW-dipping ones mainly resulted in low-grade veins or pinch-out. This suggests that the ore-controlling faults in the ore field were dominated by sinistral compressional-shearing ones at ealier stages and by dextral ones at latter stages, which corresponds to the regional stress field.5. Earlier ore fluids are marked by the magmatic origin while latter ones were mainly derived from meteor waters, as suggested by fluid inclusion geochemistry. Ore fluids apparently differ from non-mineralized ones in decrepitation curve, which are identified by moderate to lower peaks within the temperature range from 150° to 300°C. Moreover, the abundance of fluid inclusions closely correlate with gold grades, and ore-forming materialswere conspicuously derived from two distinct sources, i.e., having the mixture characteristics of mantle- and crust- substances.6. Eventually, based on synthetic analyses, this study established the metallogenetic model of ore fluids and proposed several prospect areas at different confidence levels. The Jinqingding and Sanjia gold deposits are of favorable structures and intensive hydrothermal activities. A notable improvement in gold production may be expected through exporing the deep targets of those two deposits. Needless to say, further work is also necessary to achieve that goal.