COPPER (GOLD) AND NONMETAL DEPOSITS HOSTED IN MESOZOIC SHOSHONITE ANDK-RICH CALC-ALKALINE SERIES FROM LISHUI IN THE LOWER YANGTZE REGION, CHINA

The early Cretaceous volcanic sequences from the Lishui Basin in the L ower Yangtze region may be subdivided into K-rich calc-alkaline and sh oshonite series. Geochemically, typical features of the shoshonite ser ies are high total alkali, K2O/Na2O ratio, Al2O3, Fe2O3/FeO ratio, lar ge ion lithophile elements (Rb, Ba, Tn, U, LREE) and low TiO2 and Fe c ontents. In contrast, K-rich calc alkaline series have lower K2O, Na2O and Fe2O3/FeO ratio, but are rich in Fe and Sr.The copper (gold) depo sits are associated with the shoshonite series and occur within the Gu anshan caldera, as a hydrothermal infill vein type with low to moderat e temperatures of formation. Silicification and pyritization are in cl ose relationship with Au mineralization. delta(34)S values for sulfide are -5.42 to 5.66 parts per thousand and delta(18)O values of quartz range from 8.52 to 18.53 parts per thousand. The thermoluminescent cha racteristics of gangue quartz are considered as a possible exploration indicator of Au mineralization. A large Sr deposit is hosted in high- K andesitic volcaniclastic rocks of the K-rich calc-alkaline series at Aijingshan in the Lishui Basin. The deposit is a hydrothermal vein ty pe with low to moderate formation temperatures and contains mainly cel estite with lesser kaolinite, calcite, quartz and pyrite. delta(34)S v alues of celestite and associated pyrite are 20.9 to 28.5 parts per th ousand and 7.2 to 9.5 parts per thousand respectively. The anomalies o utlined by geochemical and biochemical exploration have provided an im portant prospecting criterion for Sr deposits. The germanium (iron) de posits are hosted in fluviolacustrine sedimentary rocks which were for med in periods of volcanic inactivity. The superimposed Ge, Mn and Fe primary anomalies are an effective criterion for Ge minerarization. Th e large Jiashan bentonite deposit is hosted in volcano-sedimentary roc ks in the northern margin of the Lishui Basin,and is an alteration pro duct of these rocks. Then are 97 bentonite ore bodies in the mining ar ea in which 70 are Na-bentonites. The Na-bentonite ore bodies extend a bout 750-2400 m along strike, with 400-1200 m wide and 1-30 m thick. T he pH values and Na contents of groundwaters stored in the ore beds of bentonites in the area may be useful in exploring for the Na-bentonit e deposits buried by the Ca-bentonite.