Study on the PTX Parameters and Fractal Characteristics of Ore-Forming Fluids in the East Ore Section of the Pulang Copper Deposit, Southwest China

Abstract

In this paper, the east ore section of the Pulang porphyry copper deposit is selected as the research object. The micro-thermometer and laser Raman spectroscopic technique are utilized to study the parameters of ore-forming fluids such as pressure, temperature, and compositions. In the meantime, the fractal models, including the perimeter-area (P-A) model and number-size (N-S) model, are introduced to quantify the shape of fluid inclusions, and distinguish the stages of ore-forming fluids, respectively. The results show that the types of fluid inclusions are diversified, namely two-phase liquid-rich type, two-phase vapor-rich type, three-phase CO₂-rich type, three-phase halite-bearing type and pure liquid type. The fluids of main mineralization stage are characterized by medium-high temperature (170.2–421.4 °C), medium-high salinity (9.3 wt.%–33.3 wt.%), and low density (0.73–1.06 g/cm³). With the migration and evolution, the temperature, salinity, and pressure of ore-forming fluids gradually decrease, while the density of fluids increases. The liquid-phase compositions mainly include H₂O, and the vapor-phase compositions consist of H₂O, CH₄, N₂, and CO₂, indicating the characteristics of reducing fluids and the mixing of atmospheric precipitation. In general, the characteristics of ore-forming fluids in the east ore section are similar to those of the first mining area, suggesting that the ore-forming fluids in the east ore section may not migrate from the first mining area. And the east ore section may be a relatively independent metallogenic system. Moreover, the fractal analysis results demonstrate that the shape of fluid inclusions formed in the same hydrothermal activity features self-similarity. The D _AP values of fluid inclusions in B veins, ED veins, and D veins are 1.04, 1.06 and 1.10, respectively, showing a gradually increasing trend from the main stage to the late stage of mineralization. Meanwhile, the shape of fluid inclusions ranging from B veins to D veins becomes increasingly irregular. It also reveals that the homogenization temperature satisfies fractal distribution with four scale-invariant intervals, suggesting that all B veins, ED veins, and D veins have experienced at least four hydrothermal activities. Compared with histogram, the N-S fractal model is able to describe the distribution characteristics of the ore-forming fluids’ homogenization temperature more precisely. Therefore, it presents a potential tool for the stage division of ore-forming fluids. This research provides information about the characteristics of ore-forming fluids in the east ore section of the Pulang porphyry copper deposit, which is beneficial for further exploration in this region, and the extension of the application of fractal models in the study of fluid inclusions. However, further testing of fractal models on the fluid inclusion study is warranted to fully determine the universality.

Keywords

perimeter-area model / number-size model / fluid inclusion / fractal / Pulang copper deposit

References

[1] Afzal P, Alghalandis Y F, Khakzad A, . Delineation of Mineralization Zones in Porphyry Cu Deposits by Fractal Concentration-Volume Modeling. Journal of Geochemical Exploration, 2011, 108(3): 220-232.

[2] Ballard J R, Palin M J, Campbell I H. Relative Oxidation States of Magmas Inferred from Ce(IV)/Ce(III) in Zircon: Application to Porphyry Copper Deposits of Northern Chile. Contributions to Mineralogy and Petrology, 2002, 144(3): 347-364.

[3] Blenkinsop T G. Blenkinsop T G, Tromp P L. Fractal Measures for Size and Spatial Distributions of Gold Mines: Economic Applications, 1995, Rotterdam: Special Publication Geological Society of Zimbabwe

[4] Blevin P L, Chappell B W. Chemistry, Origin, and Evolution of Mineralized Granites in the Lachlan Fold Belt, Australia; the Metallogeny of I- and S-Type Granites. Economic Geology, 1995, 90(6): 1604-1619.

[5] Bodnar R J. A Method of Calculating Fluid Inclusion Volumes Based on Vapor Bubble Diameters and P-V-T-X Properties of Inclusion Fluids. Economic Geology, 1983, 78(3): 535-542.

[6] Bodnar R J, Burnham C W, Sterner S M. Synthetic Fluid Inclusions in Natural Quartz. III. Determination of Phase Equilibrium Properties in the System H₂O−NaCl to 1 000 °C and 1 500 Bars. Geochimica et Cosmochimica Acta, 1985, 49(9): 1861-1873.

[7] Bölviken B, Stokke P R, Feder J, . The Fractal Nature of Geochemical Landscapes. Journal of Geochemical Exploration, 1992, 43(2): 91-109.

[8] Bouzari F, Clark A H. Prograde Evolution and Geothermal Affinities of a Major Porphyry Copper Deposit: The Cerro Colorado Hypogene Protore, I Region, Northern Chile. Economic Geology, 2006, 101(1): 95-134.

[9] Burnham C W, Ohmoto H. Late-Stage Processes in Felsic Magmatism. Society of Mining Geologists of Japan, 1980, 8: 1-11.

[10] Cao K, Xu J F, Chen J L, . Origin of Porphyry Intrusions Hosting Superlarge Pulang Porphyry Copper Deposit in Yunnan Province: Implications for Metallogenesis. Mineral Deposits, 2014, 33(2): 307-322. (in Chinese with English Abstract)

[11] Carlson C A. Spatial Distribution of Ore Deposits. Geology, 1991, 19(2): 111-114.

[12] Carranza E J M. Controls on Mineral Deposit Occurrence Inferred from Analysis of Their Spatial Pattern and Spatial Association with Geological Features. Ore Geology Reviews, 2009, 35(3/4): 383-400.

[13] Carranza, E. J. M., 2009b. Geochemical Anomaly and Mineral Prospectivity Mapping in GIS. In: Hale, M., ed., Handbook of Exploration and Environmental Geochemistry. Elsevier B.V.

[14] Carranza E J M, Sadeghi M. Predictive Mapping of Prospectivity and Quantitative Estimation of Undiscovered VMS Deposits in Skellefte District (Sweden). Ore Geology Reviews, 2010, 38(3): 219-241.

[15] Chen L. The Characteristics of Ore-Forming Magma and Tectonic Setting of the Pulang Gaint Porphyry Copper Deposit in the Yunnan Province: [Dissertation], 2016, Guangzhou: Guangzhou Institute of Geochemistry, Chiese Academy of Sciences (in Chinese with English Abstract)

[16] Chen L L, Ni P, Li W S, . The Link between Fluid Evolution and Vertical Zonation at the Maoping Tungsten Deposit, Southern Jiangxi, China: Fluid Inclusion and Stable Isotope Evidence. Journal of Geochemical Exploration, 2018, 192: 18-32.

[17] Chen M G, Yu C. Study of the “Large Vein-Type” Copper Deposit of Eastern Ore-Section in Pulang Mining Area. Modern Mining, 2016, 32(3): 114-117. (in Chinese with English Abstract)

[18] Cheng Q M. The Perimeter-Area Fractal Model and Its Application to Geology. Mathematical Geology, 1995, 27(1): 69-82.

[19] Cheng Q M. Singularity of Mineralization and Multifractal Distribution of Mineral Deposits. Bulletin of Mineralogy, Petrology and Geochemistry, 2008, 27(3): 298-305. (in Chinese with English Abstract)

[20] Cheng Q M, Agterberg F P, Ballantyne S B. The Separation of Geochemical Anomalies from Background by Fractal Methods. Journal of Geochemical Exploration, 1994, 51(2): 109-130.

[21] Cheng Q M, Xu Y G, Grunsky E. Integrated Spatial and Spectrum Method for Geochemical Anomaly Separation. Natural Resources Research, 2000, 9(1): 43-52.

[22] Chi G X, Lu H Z. Validation and Representation of Fluid Inclusion Microthermometric Data Using the Fluid Inclusion Assemblage (FIA) Concept. Acta Petrologica Sinica, 2008, 24(9): 1945-1953. (in Chinese with English Abstract)

[23] Chi G X, Zhou Y M, Lu H Z. An Overview on Current Fluid-Inclusion Research and Applications. Acta Petrologica Sinica, 2003, 19(2): 201-212. (in Chinese with English Abstract)

[24] Chi Z, Ni P, Pan J Y, . Geology, Mineral Paragenesis and Fluid Inclusion Studies of the Yueyang Ag-Au-Cu Deposit, South China: Implications for Ore Genesis and Exploration. Geochemistry: Exploration, Environment, Analysis, 2018, 18(4): 303-318

[25] Fan Y H, Li W C. Geological Characteristics of the Pulang Porphyry Copper Deposit, Yunnan. Geology in China, 2006, 33(2): 352-362. (in Chinese with English Abstract)

[26] Farahmandfar Z, Jafari M R, Afzal P, . Description of Gold and Copper Anomalies Using Fractal and Stepwise Factor Analysis According to Stream Sediments in NW Iran. Geopersia, 2020, 10(1): 135-148

[27] Frezzotti M L, Tecce F, Casagli A. Raman Spectroscopy for Fluid Inclusion Analysis. Journal of Geochemical Exploration, 2012, 112: 1-20.

[28] Goldstein R H. Fluid Inclusions in Sedimentary and Diagenetic Systems. Lithos, 2001, 55(1/2/3/4): 159-193.

[29] Guo X, Du Y S, Pang Z S, . Characteristics of the Ore-Forming Fluids in Alteration Zones of the Pulang Porphyry Copper Deposit in Yunnan Province and Its Metallogenic Significance. Geoscience, 2009, 23(3): 465-471. (in Chinese with English Abstract)

[30] Gustafson L B, Hunt J P. The Porphyry Copper Deposit at El Salvador, Chile. Economic Geology, 1975, 70(5): 857-912.

[31] Hall D L, Sterner S M, Bodnar R J. Freezing Point Depression of NaCl−KCl−H₂O Solutions. Economic Geology, 1988, 83(1): 197-202.

[32] Hassanpour S, Afzal P. Application of Concentration-Number (C-N) Multifractal Modeling for Geochemical Anomaly Separation in Haftcheshmeh Porphyry System, NW Iran. Arabian Journal of Geosciences, 2013, 6(3): 957-970.

[33] Klyukin Y I, Steele-Macinnis M, Lecumberri-Sanchez P, . Densities from Ambient Temperature to Homogenization, Based on PVTX Properties of H₂O−NaCl. Earth-Science Reviews, 2019, 198: 102924

[34] Kouhestani H, Ghaderi M, Afzal P, . Classification of Pyrite Types Using Fractal and Stepwise Factor Analyses in the Chah Zard Gold-Silver Epithermal Deposit, Central Iran. Geochemistry Exploration Environment Analysis, 2020, 20(4): 496-508.

[35] Leng C B, Zhang X C, Chen Y J, . Discussion on the Relationship between Chinese Porphyry Copper Deposits and Adakitic Rocks. Earth Science Frontiers, 2007, 14(5): 199-210. (in Chinese with English Abstract)

[36] Li C J, Jiang X L, Xu Y L, . Fractal Analysis of Mesozoic ydrothermal Ore Deposits in Zhejiang. Scientia Geologica Sinica, 1996, 31(3): 266-273. (in Chinese with English Abstract)

[37] Li T F, Xia Q L, Chang L H, . Deposit Density of Tungsten Polymetallic Deposits in the Eastern Nanling Metallogenic Belt, China. Ore Geology Reviews, 2018, 94 73-92.

[38] Li T F, Xia Q L, Zhao M Y, . Prospectivity Mapping for Tungsten Polymetallic Mineral Resources, Nanling Metallogenic Belt, South China: Use of Random Forest Algorithm from a Perspective of Data Imbalance. Natural Resources Research, 2020, 29(1): 203-227.

[39] Li W C. The Tectonic Evolution of the Yidun Island Arc and the Metallogenic Model of the Pulang Porphyry Copper Deposit, Yunnan, SW China: [Dissertation], 2007, Beijing: China University of Geosciences (in Chinese)

[40] Li W C, Liu X L. The Metallogenic Regularity Related to the Tectonic and Petrographic Features of Pulang Porphyry Copper Orefield, Yunnan, and Its Ore-Controlling Characteristics. Earth Science Frontiers, 2015, 22(4): 53-66. (in Chinese with English Abstract)

[41] Li W C, Yin G H, Yu H J, . Characteristics of the Ore-Forming Fluid and Genesis of the Pulang Copper Deposit in Yunnan Province. Journal of Jilin University (Earth Science Edition), 2013, 43(5): 1436-1447. (in Chinese with English Abstract)

[42] Li W C, Zeng P S, Hou Z Q. The Pulang Porphyry Copper Deposit and Associated Felsic Intrusions in Yunnan Province, Southwest China. Economic Geology, 2011, 106(1): 79-92.

[43] Li X F, Sasaki M. Hydrothermal Alteration and Mineralization of Middle Jurassic Dexing Porphyry Cu-Mo Deposit, Southeast China. Resource Geology, 2007, 57(4): 409-426.

[44] Liu B. Density and Isochoric Formulae for NaCl−H₂O Inclusions with Medium and High Salinity and Their Applications. Geological Review, 2001, 47(6): 617-622. (in Chinese with English Abstract)

[45] Liu B. Calculation and Analysis of Fluid Inclusions, 2018, Beijing: Science Press (in Chinese)

[46] Liu B, Duan G X. The Density and Isochoric Formulae for NaCl−H₂O Fluid Inclusions (Salinity ⩽25 wt.%) and Their Applications. Acta Mineralogica Sinica, 1987, 7(4): 345-352. (Chinese with English abstract)

[47] Liu J T, Yang L Q, Lü L. Pulang Reduced Porphyry Copper Deposit in the Zhongdian Area, Southwest China: Constrains by the Mineral Assemblages and the Ore-Forming Fluid Compositions. Acta Petrologica Sinica, 2013, 29(11): 3914-3924. (in Chinese with English Abstract)

[48] Liu X D. The Evolution of Ore-Forming Fluid of the Pulang Porphyry Copper Polymetallic Deposit in the Northwest Yunnan Province, China: [Dissertation], 2018, Beijing: China University of Geosciences (in Chinese)

[49] Liu, X. D., Li, W., Yin, G., 2011. Study on the Source of Metallogenic Material and Metallogenesis of Porphyry Copper Deposit in Yunnan Province. Acta Mineralogica Sinica, Suppl.: 369–370. https://doi.org/10.16461/j.cnki.1000-4734.2011.s1.148

[50] Liu X L, Li W C, Yin G H. The Indosinian Crust Uplift-Denudation in Geza Arc of Yunnan Province and Its Geological Significance: Evidence from Biotite Geobarometer. Geoscience, 2013, 27(3): 537-540. 543–546, 628 (in Chinese with English Abstract)

[51] Lu H Z, Fan H R, Ni P, . Fluid Inclusions, 2004, Beijing: Science Press (in Chinese)

[52] Lü L. The Fissure-Vien Systerm of Pulang Copper Deposit: [Dissertation], 2014, Beijing: China University of Geosciences (in Chinese)

[53] Mandelbrot B B. The Fractal Geometry of Nature: Updated and Augmented, 1983, New York: W. H. Freeman and Company

[54] Mao Y. Study on Stable Isotope, Fluid Inclusions and Mineralization of Saishitang Cu-Polymetallic Deposit, Qinghai Province: [Dissertation], 2012, Changsha: Central South University (in Chinese)

[55] Mungall J E. Roasting the Mantle: Slab Melting and the Genesis of Major Au and Au-Rich Cu Deposits. Geology, 2002, 30(10): 915-918.

[56] Ni P, Jiang S Y, Ling H F, . The Background, Application and Development of Fluid Inclusion Planes Research. Geological Review, 2001, 47(4): 398-404. (in Chinese with English Abstract)

[57] Ni P, Pan J Y, Huang B, . Geology, Ore-Forming Fluid and Genesis of the Qiucun Gold Deposit: Implication for Mineral Exploration at Dehua Prospecting Region, SE China. Journal of Geochemical Exploration, 2018, 195: 3-15.

[58] Pan X F, Hou Z Q, Zhao M, . Stable Isotope Constraints on the Genesis of the World-Class Zhuxi W(Cu) Skarn Deposit in South China. Journal of Asian Earth Sciences, 2020, 190: 104192

[59] Pan X F, Song Y C, Wang S X, . Evolution of Hydrothermal Fluid of Dexing Tongchang Copper-Gold Porphyry Deposit. Acta Geologica Sinica, 2009, 83(12): 1929-1950. (in Chinese with English Abstract)

[60] Parry W T. Estimation of $\rm{X}_{\text{CO}_{2}}$, P, and Fluid Inclusion Volume from Fluid Inclusion Temperature Measurements in the System NaCl−CO₂−H₂O. Economic Geology, 1986, 81(4): 1009-1013.

[61] Potter R W I. Pressure Corrections for Fluid Inclusion Homogenization Temperatures Based on the Volumetric Properties of the System NaCl−H₂O. Journal of Research of the U.S. Geological Survey, 1977, 5 603-607.

[62] Qiu Y, Zhang R Q, Chou I M, . Boron-Rich Ore-Forming Fluids in Hydrothermal W-Sn Deposits from South China: Insights from in situ Raman Spectroscopic Characterization of Fluid Inclusions. Ore Geology Reviews, 2021, 132: 104048

[63] Roedder E. Ribbe P H. Fluid Inclusions. Reviews in Mineralogy and Geochemistry, 1984, Washington D.C.: Mineralogical Society of America

[64] Roedder E, Skinner B J. Experimental Evidence that Fluid Inclusions do not Leak. Economic Geology, 1968, 63(7): 715-730.

[65] Saadati H, Afzal P, Torshizian H, . Geochemical Exploration for Lithium in NE Iran Using the Geochemical Mapping Prospectivity Index, Staged Factor Analysis, and a Fractal Model. Geochemistry: Exploration, Environment, Analysis, 2020, 20(4): 461-472

[66] Sanderson D J, Roberts S, Gumiel P. A Fractal Relationship between Vein Thickness and Gold Grade in Drill Core from La Codosera, Spain. Economic Geology, 1994, 89(1): 168-173.

[67] Schertzer D, Lovejoy S. Physical Modeling and Analysis of Rain and Clouds by Anisotropic Scaling Multiplicative Processes. Journal of Geophysical Research Atmospheres, 1987, 92(D8): 9693-9714.

[68] Sillitoe R H. Some Metallogenic Features of Gold and Copper Deposits Related to Alkaline Rocks and Consequences for Exploration. Mineralium Deposita, 2002, 37(1): 4-13.

[69] Sillitoe R H. Porphyry Copper Systems. Economic Geology, 2010, 105(1): 3-41.

[70] Sterner S M, Bodnar R J. Synthetic Fluid Inclusions; X, Experimental Determination of P-V-T-X Properties in the CO₂−H₂O System to 6 kb and 700 °C. American Journal of Science, 1991, 291(1): 1-54.

[71] Sterner S M, Hall D L, Bodnar R J. Synthetic Fluid Inclusions. V. Solubility Relations in the System NaCl−KCl−H₂O under Vapor-Saturated Conditions. Geochimica et Cosmochimica Acta, 1988, 52(5): 989-1005.

[72] Touret J L R. Fluids in Metamorphic Rocks. Lithos, 2001, 55(1/2/3/4): 1-25.

[73] Turcotte D L. Fractals and Chaos in Geology and Geophysics. Journal of Fluid Mechanics, 1992, 250 690-691.

[74] Veneziano D, Furcolo P. Multifractality of Rainfall and Scaling of Intensity-Duration-Frequency Curves. Water Resources Research, 2002, 38(12): 1-12.

[75] Wang C Y, Li X F, Xiao R, . Types and Distribution of Veins in Tongchang Porphyry Copper Deposit, Dexing, Jiangxi Province. Mineral Deposits, 2012, 31(1): 94-110. (in Chinese with English Abstract)

[76] Wang K. Study on the Alteration, Vein System and Their Prospecting Significance of the Pulang Porphyry Copper Deposit, Yunnan: [Dissertation], 2017, Kunming: Kunming University of Science and Technology (in Chinese)

[77] Wang K, Jian R T, Li F, . Geological Characteristics and Prospecting of the Periphery Porphyry Copper Deposit in Pulang Area. Nonferrous Metals (Mining Section), 2016, 68(2): 40-44. (in Chinese with English Abstract)

[78] Wang K, Yang F, Li F, . Study on the Hydrothermal Alteration and Vein Systems of the Pulang Porphyry Copper Deposit in Yunnan Province. Geology and Exploration, 2016, 52(3): 417-428. (in Chinese with English Abstract)

[79] Wang S X, Zhang X C, Qin C J, . Fluid Inclusions in Quartz Veins of Pulang Porphyry Copper Deposit, Zhongdian, Northwestern Yunnan, China. Geochimica, 2007, 36(5): 467-478. (in Chinese with English Abstract)

[80] Wang Z J, Cheng Q M. Characterization of Micro-Texture of Quartz Mylonite Deformation Process Using Fractal P-A Model. Earth Science, 2006, 31(3): 361-365. (in Chinese with English Abstract)

[81] Wang Z J, Cheng Q M, Cao L, . Fractal Modelling of the Microstructure Property of Quartz Mylonite during Deformation Process. Mathematical Geology, 2007, 39(1): 53-68.

[82] Wilkinson J J. Fluid Inclusions in Hydrothermal Ore Deposits. Lithos, 2001, 55(1/2/3/4): 229-272.

[83] Wu W. Prospecting Direction of the Periphery of Pulang Copper Deposit. Yunnan Geology, 2011, 30(4): 404-406

[84] Xu G F. Prospecting Mineralogy of Gold Ore. Geology and Exploration, 1987, 2: 30-34. (in Chinese with English Abstract)

[85] Xu W G, Zhang D H, Xi B B, . Discussions on Reliability of the Decrepitation Technique Applied in Fluid Inclusion Studies: Taking the Jiangxi Dajishan Tungsten Deposit as an Example. Geoscience, 2008, 22(5): 757-765. (in Chinese with English Abstract)

[86] Yang T. Analysis on the Rocks and Ore Controlling Structures in Pulang Porphyry Copper Deposit of Shangri-La, Yunnan Province: [Dissertation], 2017, Kunming: Kunming University of Science and Technology, 1-78. (in Chinese)

[87] Zeng P S, Hou Z Q, Wang H P, . Its Geological Significance. Acta Geologica Sinica—English Edition, 2004, 78(2): 604-609

[88] Zeng P S, Mo X X, Yu X H, . Porphyries and Porphyry Copper Deposits in Zhongdian Area, Northwestern Yunnan. Mineral Deposits, 2003, 22(4): 393-400. (in Chinese with English Abstract)

[89] Zhang W H, Chen Z Y. Fluid Inclusion Geology, 1993, Wuhan: China University of Geosciences Press (in Chinese)

[90] Zhao P D, Hu W L, Li Z J. Statistical Prediction of Mineral Deposit, 1994, Beijing: Geological Publishing House (in Chinese)

[91] Zhou X D. Study on Petrological Geochemistry Characteristics of Porphyry Body in the Periphery of Pulang Porphyry Copper Deposit: [Dissertation], 2018, Kunming: Kunming University of Science and Technology (in Chinese with English Abstract)

[92] Zhou X D, Yang F, Wu J, . Petrogenesis of Porphyry Body in the Periphery of Pulang Porphyry Copper Deposit, Yunnan. Geological Science and Technology Information, 2018, 37(4): 39-50. (in Chinese with English Abstract)

[93] Zhu P P, Cheng Q M, Chen G X. New Fractal Evidence of Pacific Plate Subduction in the Late Mesozoic, Great Xing’an Range, Northeast China. Journal of Earth Science, 2019, 30(5): 1031-1040.

[94] Zuo R G, Carranza E J M. A Fractal Measure of Spatial Association between Landslides and Conditioning Factors. Journal of Earth Science, 2017, 28(4): 588-594.

[95] Zuo R G, Carranza E J M, Cheng Q M. Fractal/Multifractal Modelling of Geochemical Exploration Data. Journal of Geochemical Exploration, 2012, 122: 1-3.

[96] Zuo R G, Cheng Q M, Agterberg F P, . Evaluation of the Uncertainty in Estimation of Metal Resources of Skarn Tin in Southern China. Ore Geology Reviews, 2009, 35(3/4): 415-422.

[97] Zuo R G, Cheng Q M, Xia Q L, . Application of Fractal Models to Distinguish between Different Mineral Phases. Mathematical Geosciences, 2009, 41(1): 71-80.