Volcanic Characteristics And Their Prospecting Significance Of Fanshan In Pinghe, Fujian Province

Fanshan is located in the volcanic rock coverage area of Pinghe County in the eastof Fujian province. This area, together with the famous Zijinshan copper (gold)deposit, belongs to the Shanghang-Yunxiao NW-trending alunite and copper-goldpolymetallic ore belt. There are good regional metallogenic geological conditions andsimilar geological background in both of the two areas, with strong mineralization andalteration. Based on the studying of volcanic characteristics and ore-controllingelements of Fanshan, The contrasting approaches of geological metallogeniccondition is employed to carry out prospecting potential of the size Fanshan region. Inaddition, the author Attempts to provide any important evidences for the next phase ofexploration work.Fanshan volcanic edifice is an important part of the Ouliao Volcanic ring assembly.The petrologic feature indicates that Fanshan volcanic edifice is consisted of thecenter invasion phase, the internal effusive phase, the internal outbreak phase，theexternal effusive phase, the external eruption phase and the external sedimentaryphase from the center to the periphery of the volcano. The volcanics of Fanshan arehigh-K calc-alkaline rhyolite series, and contain high SiO2(>72.87%) and K2O(>3.66%) contents. These ignimbrites show enrichment of large ion lithophileelements (Cs、Rb、Ba、Th、U) and depletion of high field-strength elements (Ta、Nb、Sr、Ti). They show relatively high total REE contents and LREE/HREE ratios.The geochemical characteristics of the volcanics are analyzed to reveal their tectonicenvironment, and the results indicate that Fanshan volcanics formed in the extensionaltectonic subduction orogeny after the collision of plates. The major elementcharacteristics are similar with the continental crust remelting granites in the southeastcoast of China. in addition, the REE also indicates its crustal origin.LA-ICP-MS zircon dating results imply that these ignimbrites formed at the age of137.9~141.7Ma, namely the Late Jurassic-Early Cretaceous. In addition, anotherlater volcanic activity happened in the late Early Cretaceous (109.18±0.62Ma). Thecomparative study approaches are employed to find that the geological setting in Fanshan and Zijinshan areas are similar. Both of the two areas located in the junctionof NE and NW-trending regional structural, and have the same ore controllingstructures. in addition, the rock characteristics, mineralization and alteration types,and the geochemical field future are similar each other. At last we can conclude thatthe Fanshan area have favorable Metallogenic geological conditions and hugeprospecting potential, and is an advantage location to seek for epithermal, porphyrycopper-gold polymetallic ores.