| Turquoise is a surface mineral formed from weathering and leaching of volcanic or sedimentary rocks containing copper,phosphorus,and aluminum by surface and atmospheric water.China has abundant turquoise resources and is one of the major consumer countries of turquoise,with a rich cultural heritage in turquoise.The origin of turquoise is one of the determining factors for market pricing.Source tracing technology is a key point for identifying the origin of turquoise and tracking the flow of unearthed turquoise resources.Although foreign countries have established relatively mature and complete turquoise source tracing technology,research in China is still fragmented,and there are bottlenecks in source tracing technology that need to be overcome.Therefore,this study systematically sorts out the characteristics of turquoise from various areas in China,identifies accurate trace elements unique to the turquoise source,explores a Chinese characteristic turquoise source tracing technology,and applies it to solve the problem of the origin of unearthed turquoise resources,which has significant practical application value and academic research value.This thesis focuses on the turquoise from 15 places of origin,including modern mineralization sites,mineralization points,and ancient mineralization sites in China.Based on a clear understanding of the geological background and ore genesis of turquoise from each place of origin,the turquoise from various producing areas is systematically and detailedly studied in terms of gemmology,mineralogy and geochemistry.Using the concepts of mining areas,mining belts,and mining sites,the study summarizes the commonalities and differences of turquoise from different mining areas,mining belts,and mining sites in terms of basic gemological characteristics,surrounding rocks,impurity minerals,structure,trace elements,rare earth elements,and isotopes,and selects key characteristic information for identifying the origin of turquoise.With the help of trace elements and multivariate statistics,a model for identifying the origin of turquoise is established.Based on this,a cross-validation method and a layer-by-layer tracing method are used to improve the accuracy of source tracing of unearthed turquoise and construct a complete technology and system for source tracing of unearthed turquoise.Technological analysis and source research of turquoise unearthed from Liangzhu,Erlitou,Panlongcheng,Yejiashan and Qiaojiayuan are also carried out.And the effects of weathering on the source tracing results of unearthed turquoise are evaluated to verify the practicality and reliability of the source tracing technology.The research content and results are as follows:1.The genesis types of turquoise deposits can be divided into sedimentary-metamorphic rock types and igneous rock types according to the difference of turquoise ore type.The ore-bearing rock of sedimentary-metamorphic rock-type turquoise are black rock series.Among them,the turquoise deposits in the southern mining belt of the junction of Hubei,Henan and Shaanxi provinces occur in the carbonaceous mudstone and siliceous mudstone of the Zhuangzigou Formation;the turquoise in the central mining belt is exposed in the black rock series of the Cambrian Shuigoukou Formation;and the turquoise in the northern mining belt is exposed in the Carboniferous Bai Zhugou Formation and black carbonaceous mudstone.The Hami turquoise deposit occurs in the siliceous rock of the Cambrian Pochengshan Formation.The genesis of turquoise deposits in Anhui is related to igneous rocks and belongs to iron ore-associated deposits.The Penjia mountain turquoise in Ma’anshan is exposed in the volcanic andesite of the Da Wangshan Formation of the Lower Cretaceous,and the Tongling turquoise is inferred to be exposed in the Shuangmiao Formation of the Early Cretaceous based on its geographical location.2.The origin tracing technology for unearthed turquoise can be carried out in the following four steps:1)Firstly,preliminary diagnosis of the ore-forming type can be made based on the gemological characteristics.The surrounding rocks of magmatic-type turquoise are all metamorphic rocks,often containing carbonaceous components,and are dark in color.The surface of turquoise often has black iron lines.The surrounding rocks of volcanic rock-type turquoise are light-colored andesite and diorite.The surface of turquoise often has"white spots".The density of turquoise in Ma’anshan is relatively low,and the color of blue turquoise is characterized by"positive"and"yang".2)From the mineralogical characteristics,primary identification is made.APS minerals and graphite or amorphous carbon are found in sedimentary type impurities.Hematite is most commonly seen as needle-like minerals,and yellow iron ore can be found in the surrounding rock of Xiaodonggou and Wenfeng turquoise,while it is rare in turquoise containing turquoise.Hornblende in Lasan turquoise is commonly associated with sphalerite,while phosphorus alumina is commonly associated with Wenfeng turquoise.Miaoshanzhai is rich in Se minerals,mainly selenium,as well as selenocopper and cuproselenide.Xiaodonggou turquoise contains chlorite.Needle-like minerals,fibrous serpentine,and viseite are commonly found in river mouth turquoise.Argentite,apatite,and barium aluminum phosphate are commonly found in Guaiyu turquoise.Kaolinite and strontium sulfide aluminum phosphate are the primary minerals found in Xichuan turquoise,while phosphorus aluminum strontium sulfide is the primary mineral in Tianhu Dong turquoise,which also contains the key mineral,chlorite copper.In magmatic-type impurities,the mineral combination of kaolinite and sodium feldspar is most typical.Moreover,Ma’anshan turquoise in Anhui contains more yellow iron ore.Turquoise can exhibit a variety of shapes and forms,including platy,tabular,rhombic-tabular,columnar,plate-columnar,thick plate-like,long columnar,spherical,renal,radial-spherical,spiral,and floral clusters.The turquoise with a light texture and loose microcrystals has a higher porosity.Xichuan turquoise has the poorest crystallinity,and the microcrystals are small.The microcrystals of turquoise from other sources have a moderate to good degree of crystallinity.3)Based on trace elements and isotopes,accurate source tracing is performed.The average contents of trace elements Na,Ca,Cr,Zn,Sb,and U in sedimentary-type turquoise are higher than those in volcanic rock-type turquoise.Sedimentary-type turquoise is enriched in U,Be,Mo,and Zn,with contents higher than that of the continental crust.Ba,V,and Cr are commonly enriched in most sedimentary rock-type turquoise,and the average enrichment coefficients of U,Mo,Zn,Cr,and Li are significantly higher than those of volcanic rock-type turquoise.Turquoise from the junction of Hubei,Henan and Shaanxi provinces has high contents of Ba,Zn,Zr,Sb,and U,while turquoise from the Tianhu Dong mining area in Xinjiang has high contents of trace elements Li,Be,Na,K,V,Cr,Sr,and Ga.Sc is relatively high in volcanic rock-type turquoise,while Co is relatively high in Ma’anshan turquoise,and its distribution range is large.The contents of other trace elements are relatively low.Compared with the continental crust,volcanic rock-type turquoise is enriched in Be,Zn,and Sc.The combination of trace elements and multivariate statistical methods can effectively identify the origin of turquoise with an accuracy rate of over 99%.The 87Sr/86Sr ratio of Yungaisi and Guaiyu turquoise is between 0.7078 and 0.7109 and 0.7173 and 0.7242,respectively,which have significance in identifying the origin.4)Using the cross-validation method of multiple evidence and comprehensively analyzing the characteristics of the origin from the mineralization type,mining area,mining belt,and mining site,the origin of the turquoise can be traced step by step.3.During the erosion process after burial in the tomb,the unearthed turquoise underwent physical and chemical weathering and chemical adsorption.Physical and chemical weathering caused the dissolution and loss of the major components Al2O3 and P2O5,accompanied by the loss of trace elements Cr,Co,and U.The surface micro-pores increased,resulting in whitening,forming a weathering layer（about several tens of micrometers thick）.The particles in the weathering layer became finer,the edges of the particles became smooth,and the gaps between the particles were not clear.During the process of infiltration,six trace elements,Pb,Th,Mg,Ni,Na,and K,were also adsorbed.4.The turquoise of the Liangzhu culture mainly came from the southern mining belt of the Eyu Shan mining area,with a small amount coming from the northern mining belt.The turquoise of the Erlitou culture mainly came from the northern mining belt of the Eyu Shan mining area.Turquoise unearthed from the Panlongcheng and Yejia Mountain sites has the characteristic of multiple sources,but mainly comes from the southern mining belt of the Eyu Shan mining area,with some from the northern mining belt.The turquoise unearthed from the Qiaojia Yuan cemetery comes from Zhushan,Hubei.During the pre-Qin period,the ancestors of China adhered to the principle of"mining nearby resources"and exploited turquoise resources,with the southern and northern mining belts of the Eyu Shan mining area being the main mining sites. |
