| North Guandong Nanling metallogenic belt is one of the most important area of tungsten tin polymetallic ore belt.Four large-sized deposits,5 medium-sized deposits,and more than 30 small deposits and mineralized bodies are found there.The area is dominated by quartz vein type wolframite mineralization.In recent years,a large scale of tungsten mineralization was found in the altered pluton deep in Hongling deposit.Hongling and Yaoling tungsten deposits both have two members that quartz vein wolframite mineralization developed at the upper part while skarn type scheelite mineralization developed at the lower part.Clearly to understand this two member structure,has an important significance for the deep prediction of northern Guangdong quartz vein type Shirenzhang,Mei Ziwo,Jubankeng deposits.The concentrated distribution of tungsten tin polymetallic deposits and various types of mineralization have made the northern Guangdong an ideal site for the study of tungsten and tin mineralization.The large-scale mineralization in Nanling region occurred in the Yanshan period,and the main body formed roughly in two time periods,respectively,ca.159 Ma and 138 Ma.The study of ore deposits is important to solve the problems closely related to metallogenic prognosis,so as to meet the needs of prospecting prediction,and become an important issue of practical significance and scientific research value.Because of the differences of object,means and method,the understanding of the relationship between rock mass and mineralization,the main source and proportion of ore-forming fluid is quite different.It is key of the study of this kind of deposit that how to link the exposed granite or tungsten tin mineralized granite with quartz vein type tungsten tin mineralization,and to analyze the relationship between them and their mineralization difference.Through in-depth study of the relationship between regional granite and tungsten tin mineralization,it has positive guiding significance to guide the prospecting of the northern Guangdong region.In recent years,more and more scholars have studied the plutons related to tungsten mineralization.It is believed that began from the disseminated wolframite scheelite in magma,through greisen veins by magmatic liquid differentiation,to pegmatite shell,then quartz vein,which reflects the evolution from magma to magmatic hydrothermal period.With the change of different mineralization types,the mineral assemblages and structures have changed systematically,corresponding with changes of chemical composition and fluid inclusion properties.The magmatic stage,transition stage,and hydrothermal stage are commonly exist in quartz vein type and greisen tungsten deposits.Magma ot hydrothermal evolution process is continuous,and between the two stage developed intermediate transition fluid.The characteristics of this continuous evolution are well represented in skarn type tungsten deposits.Through the study of the geological characteristics,mineralization chronology,fluid inclusions,O-H-S-Pb isotopes,the major-trace elements changes during alteration process,and primary halo in drills,the features of geological body,ore-forming contact structure and mineralization indicator of Hongling rock-alteration type sheelite and quartz-vein type wolframite deposit were confirmed.Based on the data of production and scientific research,the prospecting geological model of Hongling tungsten mine is set up.The main conclusions are as follows:1.characteristics of metallogenic geological bodies,metallogenic structural planes and mineralization indicator:After systematically studying the characteristics of fine grained muscovite granite in the third and fourth stages of Hongling tungsten mine,we combined the two stages.We found that liquid differentiation has important significance to mineralization.Liquid differentiation is a role in magmatism and hydrothermal activity,which resulted in further enrichment of metallogenic elements of the third stage pluton.Both the zircon U-Pb age of granite and molybdenite Re-Os age of quartz vein type tungsten deposit are consistent within the experimental error range.This result indicates that diagenesis and mineralization should belong to the same tectonic period,and may have genetic relationship.The shape of rock type tungsten ore is controlled by the third stages of rock mass shape.Combined with multi-element isotope comparison,it is determined that the ore-forming geological body of Hongling tungsten mine is the third stage medium to fine grained muscovite granite.The rock-type tungsten ore is controlled by the top contact zone of the third stage rock,and the lower interface is basically limited to the liquid separation interface.The metallogenic structure of quartz vein type tungsten ore is controlled by the fracture structure and joint fracture.The overall distribution of Hongling tungsten vein is the NW to SE trending,curtain like arranged in plane.The veins converge to No.305 exploration line in the Central Mining Area.Quartz vein may cut through the rock body type tungsten body and pitchout in the deep.Hongling tungsten ore has obvious alteration zoning.From deep to shallow,there are K-feldspar belt,albite belt,greisenization belt,fluorite and iron lithium mica belt.The near wall rock alteration of rock type tungsten deposit is greisenization.Characteristic of Li ladder distribution,F rising linearly to the top of rock mass,and tungsten mineralization with prosodic features are developed in the primary halo.Alteration geochemistry shows that the surrounding altered rock tends to enrich Cu,Mo and so on,while slightly lack of W.The ore-forming fluid of rock type tungsten ore is mainly derived from magmatic water,while that of quartz vein type tungsten ore is mainly compounded of magmatic water and meteoric water.By S,Pb,Sm,Nd and other isotopes studies,the ore-forming materials of both the rock type tungsten ore and quartz vein type tungsten deposit are magmatic.2.Geological model for prospecting predictionThe high temperature hydrothermal type tungsten-tin deposit is formed by the intrusion of high volatile acid magma.The deposit is formed in the late stage of magmatic differentiation with neutral to basicity and high volatile.In the contact zone or vicinity,pegmatite shell or veins are often developed.When the pressure produced by post magmatic hydrothermal intrusion is greater than the pressure of surrounding rock,strong hydraulic fracture zone is formed.Since deep pressure force decreasing from the bottom up,so the "five storey" vein vertical distribution with upper thin and lower rough often formed;when the post magmatic hydrothermal intrusion pressure is less than the surrounding rock pressure,in the regional crack system formed the single vein type deposit.The inner and outer contact zones at the top of the intrusive body are the metallogenic centers.At the upper part of the ore body is usually a kind of fluorite or tourmaline,while the ore peripheral alteration is greisenization,showing alteration zoning.The alteration zoning reflects the evolution process of the ore-forming hydrothermal system from high temperature alkaline to medium high temperature and finally to low temperature acidity,and the mineralization is mainly carried out in medium high temperature and neutral conditions.Vein type tungsten mineralization mainly occurs in the outer contact zone within the range of 1 to 1.5km,and the internal contact zone within the range of 300 to 500m;the rock type tungsten mineralization and greisen type mineralization mainly occur in the contact zone within the range of 300 m.Rock type mineralization has special characteristics of Li and F primary halo.Surface prospecting indications: first,geological body analysis.Through the analysis of regional tectonic background,geology,geophysical prospecting and remote sensing,the existing possibility of ore-forming related rock mass will be assessed.Second geochemical anomalies.There should be a geochemical anomaly assemblage associated with ore-forming elements,such as the anomalies of surface Cu,Mo,F,and negative W anomalies.Third,there is quartz vein type tungsten deposit on the surface,in which mica and quartz lines and fine vein belts are important prospecting marks.Fourth,there is a large area of fluorite and silicification alteration on the surface.Vertical drilling marks: 3 key signs of ending hole drilling practice(mineralization ended marks)for prospecting in Hongling area are summed up.First,drilling through the ore rock,namely muscovite granite of the third stage;second,hitting the albitization of potash feldspathization overall with not mine;third,drilling through more than 2 mineralization rhythm with no industrial mineralization. |
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