A Studyon Metallogenetic Regularity And Prognosis Of Concealed Ore Body In Southern Great Xing'an Range, Northeastern China

Located at the eastern segment of the Central Asia Orogenic Belt,the southern Great Xing'an Range?SGXR?is situated in a superposition area caused by the Paleo-Asia tectonic-metallogenic domain and the Western Paleo-Pacific tectonic–metallogenic domain.The SGXR is one of the most important areas of nonferrous metal mineral resources and also contains signicant amounts of fluorite resources.However,some key issues such as metallogenic regularity and metallogenic prediction related to fluorite deposits remain ambiguous.Herein,based on a systematic investigationof representative fluorite deposits in the SGXR,we integrate regional relevant geological,geochronological,geophysical and geochemical information to evaluate the ore-forming processes.Finally,metallogenic prediction is carried out within the study area.This work obtained the following achievements and innovations:1.Fluorite deposits in the SGXR,which share similar geologic features,are mainly of structure-related hydrothermal vein-type.It is no selectivity for fluorite mineralization to wall rocks.Ore bodied are mainly controlled by NNE-trending structures and commonly occur as veins and lenses.Ore mineralogy of fluorite deposits are composed essentially of fluorite and quartz.Wall rock alterations are dominated by sets of medium-low temperature hydrothermal alterations.2.The Sm-Nd isochron age of fluorites from Shuitou deposit is 132±11 Ma,and the calcites from the Sandaoyingzi deposit yield a Sm-Nd isochron age of 136.5±4.3 Ma,indicating that the major mineralization stage occurred during early Cretaceous?137-132 Ma?.The widespread fluorite vein systems in the SGXR are closely link to the period of tectonic transfer in northeast Asian which is characterized by the transformation from NNE-trending contraction to NNE-trending extension during the early Cretaceous.Subsequent regional extension and lithosphere thinning occurred,which triggered widespread fluorite mineralization in this region.3.Homogenization temperatures and salinities of the fluid inclusions mainly range from160 to 240°C and 0.86 to 0.891 g/cm³,respectively.The calculated densities show average value of⁰.88 g/cm³.Laser Raman spectra show that both the vapor and liquid compositions of the inclusions are dominated by H₂O.The C-H-O isotopic features suggest that the ore-forming fluids are of meteoric water origin.Furthermore,Latitude effect on?D values of the fluorite deposits in the Eastern China was mentioned in this contribution.The ore-forming fluids can be mainly attributed to NaCl-H₂O system with moderate to low temperature,low salinity and low density.There is no evidence for post-magmatic hydrothermal fluid.The ore-forming fluid shows a meteoric water source,with water-rock reaction as the main mechanism for fluorite precipitation.4.The individual orebodies in this region exhibits a well-developed vertical zonation.Vertically,the orebodies can be divided into four parts:uppermost,upper,central,and lower.The nature of the orebodies?such as mineralization feature,ore fabric,wall rock alteration,ore grade?show a regular change pattern from top to bottom.The recognition of vertical zonation could be effectively applied for fluorite resources exploration5.Based on the study of metallogenic regularity and prospecting criteria,combined with comprehensive exploration methods,we make a prediction of concealed ore bodied in the Shuitou and Xiaobeigou fluorite deposit and yield significant results.Great exploration potential?large scale?exists in thesetarget areas.