The Sadaigoumen molybdenum deposit is a large-scale porphyry molybdenum deposit discovered in the 1980s on the northern margin of the North China Craton. Previous studies have mainly focused on its metallogenic regularity, whereas the genetic relationship between the two ore-hosting rocks (the red monzogranite and the white monzogranite) and their link to mineralization remains controversial. Based on detailed geological surveys and engineering verification, this study presents petrological, mineralogical, geochemical, and geochronological data to investigate their genetic connection, diagenetic processes, and constraints on mineralization. Zircon U-Pb dating yields emplacement ages of (247.2 ± 2.0) Ma and (245.1 ± 1.8) Ma for the red and white monzogranites, respectively, indicating coeval Middle Triassic magmatism. Both granites show similar geochemical characteristics: high SiO₂, Al₂O₃, K₂O, and total alkali contents; A/CNK=1.34 - 1.46; enrichment in Rb, K, Th, U, and LREEs; depletion in Nb, Ta, Ti, P, and HREEs; and variable negative Eu anomalies. Biotite in both monzogranites is dominated by crust-derived ferruginous biotite, with minor magnesian biotite. The results demonstrate that both monzogranites are high-silica, high-K, peraluminous I-type shoshonitic series granites. They share a similar origin and tectonic setting, derived from partial melting of the lower crust, with comparable P-T conditions, emplacement depths, and oxygen fugacity, all favorable for Mo enrichment and migration. In summary, the two represent the same pluton emplaced in a post-collisional extensional setting. The main body formed as red monzogranite during magma cooling and crystallization, whereas the white monzogranite is a later product of kaolinization alteration. Molybdenum mineralization occurred subsequently, together forming a typical example of a continuous Middle Triassic magmatic-molybdenum mineralization event in the Yanliao area, northern margin of the North China Craton.
采集具有代表性的1件红色二长花岗岩(G02样品)和1件白色二长花岗岩样品(G03样品),用来完成锆石U-Pb定年(图1(c);表1)。锆石单矿物颗粒的挑选、制靶及相关照相工作均在河北省区域地质调查院实验室完成。具体流程如下:首先将小块岩石人工破碎,采用电磁选与重液分选法分离出重矿物,随后放置于双目显微镜下,经人工观察并挑选出所有锆石颗粒。锆石制靶及光学显微照相同样于该实验室进行。选取晶形完整、透明度较高的单颗粒锆石,制成环氧树脂靶后,经打磨抛光,依次在反射光、透射光及阴极发光下进行图像采集。实验所用阴极发光系统为GATAN MINI CL,电子光学显微系统为日本电子扫描电镜JSM-6510。综合对照所获得的锆石靶反射光、透射光与阴极发光图像,在避开裂隙和包裹体的基础上,选择洁净、透明且环带清晰的区域作为分析点位。
JIANGS H, LIANGQ L, BAGASL. Re-Os ages for molybdenum mineralization in the Fengning region of northern Hebei Province, China: New constraints on the timing of mineralization and geodynamic setting[J]. Journal of Asian Earth Sciences, 2014, 79: 873 - 883.
[7]
SUNZ J, WANGZ Q, YUH N, et al. Geochronology, geochemistry, and Hf Isotope of the granites from the Mo deposits in Fengning region, China: Implications for tectonic evolution and mineralization of the North China Craton[J]. Arabian Journal of Geosciences, 2019, 12(14): 434.
[8]
SUNZ J, WANGZ Q, YUH N, et al. Geochemistry, zircon U-Pb, and molybdenite Re-Os geochronology of the Mo deposit in Fengning region, Hebei Province, China[J]. Geological Journal, 2019, 54(6): 3619 - 3642.
[9]
WANGC Y, SUNZ J, LIUG H, et al. Zircon U-Pb geochronology and geochemistry of the intrusions from the Sadaigoumen Mo deposit in the northern margin of the North China Craton: Implications for mineralization process and tectonic evolution[J]. Geological Journal, 2020, 55(1): 949 - 966.
[10]
CHENP W, ZENGQ D, ZHOUT C. Petrogenesis and Mo prospecting significance of Sadaigoumen granites on the northern margin of the North China Craton[J]. Journal of Geochemical Exploration, 2020, 214: 106536.
ZHAOG C, SUNM, WILDES A, et al. Late Archean to Paleoproterozoic evolution of the North China Craton: Key issues revisited[J]. Precambrian Research, 2005, 136(2): 177 - 202.
[13]
WANGG R, WUG, XUL Q, et al. Molybdenite Re-Os age, H-O-C-S-Pb isotopes, and fluid inclusion study of the Caosiyao porphyry Mo deposit in Inner Mongolia, China[J]. Ore Geology Reviews, 2017, 81: 728 - 744.
LIUY S, GAOS, HUZ C, et al. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology, 2010, 51(1/2): 537 - 571.
[16]
LUDWIGK R. User’s manual for isoplot 3.75: A geochronological toolkit for Microsoft Excel (Special Publication No.5) [R]. Berkeley: Berkeley Geochronology Center, 2012: 76.
[17]
MIDDLEMOSTE A K. Naming materials in the magma/igneous rock system[J]. Earth-Science Reviews, 1994, 37(3/4): 215 - 224.
[18]
MANIARP D, PICCOLIP M. Tectonic discrimination of granitoids[J]. Geological Society of America Bulletin, 1989, 101(5): 635 - 643.
[19]
SUNS S, MCDONOUGHW F. Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes[J]. Geological Society, London, Special Publications, 1989, 42(1): 313 - 345.
[20]
FOSTERM D. Interpretation of the composition of trioctahedral micas[R]. Washington: United States Geological Survey, 1960: 11 - 49.
EBYG N. Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications[J]. Geology, 1992, 20(7): 641.
[31]
KINGP L, WHITEA J R, CHAPPELLB W, et al. Characterization and origin of aluminous A-type granites from the Lachlan fold belt, southeastern Australia[J]. Journal of Petrology, 1997, 38(3): 371 - 391.
[32]
CHAPPELLB W, WHITEA J R. I- and S-type granites in the Lachlan fold belt[J]. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 1992, 83(1/2): 1 - 26.
RUDNICKR L, FOUNTAIND M. Nature and composition of the continental crust: A lower crustal perspective[J]. Reviews of Geophysics, 1995, 33(3): 267 - 309.
[52]
RAPPR P, WATSONE B. Dehydration melting of metabasalt at 8 - 32 kbar: Implications for continental growth and crust-mantle recycling[J]. Journal of Petrology, 1995, 36(4): 891 - 931.
STERNC R, KILIANR. Role of the subducted slab, mantle wedge and continental crust in the generation of adakites from the Andean Austral Volcanic Zone[J]. Contributions to Mineralogy and Petrology, 1996, 123(3): 263 - 281.
[55]
WONESD R, EUCSTNNH P. Stability of biotite: Experiment, theory, and application[J]. American Mineralogist, 1965, 50: 1228 - 1272.
[56]
KEPPLERH, WYLLIEP J. Partitioning of Cu, Sn, Mo, W, U, and Th between melt and aqueous fluid in the systems haplogranite-H2O-HCl and haplogranite-H2O-HF[J]. Contributions to Mineralogy and Petrology, 1991, 109(2): 139 - 150.
[57]
WEBSTERJ D, SINTONIM F, DE VIVOB. The partitioning behavior of Cl, S, and H2O in aqueous vapor- ±saline-liquid saturated phonolitic and trachytic melts at 200 MPa[J]. Chemical Geology, 2009, 263(1/2/3/4): 19 - 36.
WATSONE B, HARRISONT M. Zircon saturation revisited: Temperature and composition effects in a variety of crustal magma types[J]. Earth and Planetary Science Letters, 1983, 64(2): 295 - 304.
[63]
HENRYD J, GUIDOTTIC V, THOMSONJ A. The Ti-saturation surface for low-to-medium pressure metapelitic biotites: Implications for geothermometry and Ti-substitution mechanisms[J]. American Mineralogist, 2005, 90: 316 - 328.
CARROLLM R, RUTHERFORDM J. Sulfur speciation in hydrous experimental glasses of varying oxidation state: Results from measured wavelength shifts of sulfur X-rays[J]. American Mineralogist, 1988, 73(7/8): 845 - 849.
[71]
CANDELAP A, BOUTONS L. The influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite[J]. Economic Geology, 1990, 85(3): 633 - 640.
[72]
BALIE, KEPPLERH, AUDETATA. The mobility of W and Mo in subduction zone fluids and the Mo-W-Th-U systematics of island arc magmas[J]. Earth and Planetary Science Letters, 2012, 351/352: 195 - 207.
[73]
MENGASONM J, CANDELAP A, PICCOLIP M. Molybdenum, tungsten and manganese partitioning in the system pyrrhotite-Fe-S-O melt-rhyolite melt: Impact of sulfide segregation on arc magma evolution[J]. Geochimica et Cosmochimica Acta, 2011, 75(22): 7018 - 7030.
[74]
FOLEYS F, WHELLERG E. Parallels in the origin of the geochemical signatures of island arc volcanics and continental potassic igneous rocks: The role of residual titanates[J]. Chemical Geology, 1990, 85(1/2): 1 - 18.
[75]
CONDIEK C. Plate Tectonics and Crustal Evolution[M]. 2nd ed. New York: Pergamon Press, 1982:400.
[76]
LIEGEOISG P. Preface: some words on the post-collisional magmatism[J]. Lithos, 1998, 45: 15 - 17.
[77]
PEARCEJ A, HARRISN B W, TINDLEA G. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J]. Journal of Petrology, 1984, 25(4): 956 - 983.
[78]
BATCHELORR A, BOWDENP. Petrogenetic interpretation of granitoid rock series using multicationic parameters[J]. Chemical Geology, 1985, 48(1/2/3/4): 43 - 55.
ZHANGX H, ZHANGH F, JIANGN, et al. Early Devonian alkaline intrusive complex from the northern North China Craton: A petrological monitor of post-collisional tectonics[J]. Journal of the Geological Society, 2010, 167(4): 717 - 730.
PEIF P, ZHANGY, WANGZ W, et al. Early-Middle Paleozoic subduction-collision history of the south-eastern Central Asian Orogenic Belt: Evidence from igneous and metasedimentary rocks of central Jilin Province, NE China[J]. Lithos, 2016, 261: 164 - 180.
[87]
LIUY J, LIW M, FENGZ Q, et al. A review of the Paleozoic tectonics in the eastern part of Central Asian Orogenic Belt[J]. Gondwana Research, 2017, 43: 123 - 148.
[88]
DUJ Y, TAON, JIANGB, et al. Recognition of Late Carboniferous arc-related volcanic rocks from Ongniud Banner, southeastern Inner Mongolia: Evidence of southward subduction and implication of closure time for Palaeo-Asian Ocean[J]. Geological Journal, 2021, 56(9): 4499 - 4522.
SHIY, SHIS S, LIUZ H, et al. Back-arc system formation and extinction in the southern Central Asian Orogenic Belt: New constraints from the Faku ophiolite in north Liaoning, NE China[J]. Gondwana Research, 2022, 103: 64 - 83.
[91]
ZHANGS H, ZHAOY, DAVISG A, et al. Temporal and spatial variations of Mesozoic magmatism and deformation in the North China Craton: Implications for lithospheric thinning and decratonization[J]. Earth-Science Reviews, 2014, 131: 49 - 87.