Types, characteristics of apatite and its metallogenic indications in the Oubulage porphyry copper-gold deposit, Inner Mongolia

doi:10.13745/j.esf.sf.2024.12.128

Abstract

Abstract:

The Oubulage porphyry Cu-Au deposit, situated in the Langshan metallogenic belt within the Central Asia-Mongolia metallogenic province, represents a typical magmatic-hydrothermal system. Petrographic analysis, cathodoluminescence (CL) imaging, and major-trace element geochemistry reveal two distinct generations of apatite. The first type (Ap-I) occurs as inclusions within hornblende and biotite, showing coarse grain sizes (100-200 μm), euhedral morphologies, and dark green to brown CL emissions—features indicative of direct crystallization from a silicate melt. In contrast, the second type (Ap-II) is mainly distributed along mineral fractures related to fluid activity and is paragenetic with sulfides, calcite, phengite, K-feldspar, albite, and rutile, forming a fluid-dominated mineral assemblage. Ap-II is finer-grained (30-50 μm), exhibits euhedral to subhedral forms, and emits green to yellowish-green CL, reflecting crystallization from volatile-rich hydrothermal fluids. Compared with Ap-I, Ap-II shows higher concentrations of F, SiO₂, Al₂O₃, MnO, and SO₃, along with elevated δEu values, and lower Ga contents and Th/U ratios—implying involvement of oxidized, F-, Si-, Al-, and Mn-rich fluids. Additionally, Ap-II is enriched in W, Bi, and Sn, displays higher Nb/Ta ratios than mantle values, and corresponds to a formation temperature of 784.7 ℃ (based on the Zr-in-rutile thermometer), suggesting the ore-forming fluids were high-temperature, supercritical in nature. The presence of radial fractures in early-formed Ap-I, garnet, and other minerals further indicates the influence of fluid overpressure. Collectively, these features point to deep-sourced, oxidized, high-temperature supercritical fluids enriched in F, Si, Al, and Mn that played a key role in metal transport and mineralization.

Key words: Apatite, F- and Si-rich supercritical fluid, fluid overpressure, Oubulage porphyry copper-gold deposit, Inner Mongolia

CLC Number:

ZHONG Jingyu, ZHANG Yanan, SU Shangguo, CHEN Xuegen. Types, characteristics of apatite and its metallogenic indications in the Oubulage porphyry copper-gold deposit, Inner Mongolia[J]. Earth Science Frontiers, 2025, 32(5): 308-325.

Figures/Tables 14

Fig.1 Tectonic location map of the study area. Modified after [32].

Fig.2 Geological map of the mining area of the Oubulage porphyry copper-gold deposit (a) and sectional diagram of the ore body (b)

Fig.3 Microscopic characteristics of two types of apatite in the Oubulage Cu-Au deposit (a) Apatite is enclosed within hornblende; (b) Apatite in the quartz porphyry matrix; (c) Apatite distributed within sulfides; (d) Garnet fractured and filled with mineral assemblage of rutile, apatite, and K-feldspar. Ap—apatite; Hb—hornblende; Sul—sulfides; Grt—garnet; Kp—K-feldspar; Rt—rutile.

Fig.4 CL images of two types of apatite in the Oubulage Cu-Au deposit Ap—apatite; Hb—hornblende; Cal—calcite; Rt—rutile; Sul—sulfides; Qtz—quartz. (a) CL image of apatite encluded within hornblende; (b) CL image of broken hornblende filled with calcite and apatite; (c) CL image of the paragenetic assemblage of calcite, rutile and apatite; (d) CL image of quartz and apatite distributed in sulfides.

Table 1 Major element contents of apatite

Fig.5 Major element plots of apatite in the Oubulage Cu-Au deposit

Table 2 Content of trace elements in apatite

Fig.6 Chondrite-normalized REE pattern diagram of apatite. The normalized values adapted from [38].

Fig.7 Diagrams of apatite SiO2-FeO (a) and SiO2-MnO (b). Adapted from [24].

Fig.8 Binary diagram of trace elements in apatite

Table 3 Major elements of rutile

样品号	w_B/%
样品号	Al₂O₃	Cr₂O₃	FeO	Nb₂O₅	SiO₂	SnO₂	Ta₂O₅	TiO₂	V₂O₃	WO₃	ZrO₂	K₂O	CaO	Total
B1-Rt-1	0.07	0.02	0.63	0.62	0.06	0.79	0.07	97.04	0.41	0.25	0.30	—	—	100.26
B1-Rt-2	0.03	0.01	0.50	0.54	0.14	0.27	0.03	98.01	0.31	0.04	0.12	—	—	100.00
B1-Rt-3	0.07	—	0.65	0.47	0.27	0.28	0.04	97.42	0.34	0.20	0.09	—	—	99.83
B1-Rt-4	0.12	0.02	0.55	0.58	0.34	0.28	0.09	96.58	0.25	0.40	0.11	—	—	99.32
B1-Rt-5	0.03	0.05	0.66	0.45	0.17	0.44	0.05	97.20	0.51	0.26	0.14	—	—	99.96
B2042-Rt-1	0.45	—	1.72	—	0.32	—	—	96.03	—	—	0.11	0.18	0.04	98.85
B2042-Rt-2	0.21	0.02	1.03	—	0.12	—	—	98.58	—	—	0.11	0.17	0.04	100.28
B2042-Rt-3	0.31	—	2.19	—	0.30	—	—	95.70	—	—	0.16	0.07	0.07	98.80
B2042-Rt-4	0.28	—	0.96	—	0.08	—	—	98.79	—	—	0.17	0.16	0.04	100.48
B2042-Rt-5	0.32	—	0.33	—	0.48	—	—	97.87	—	—	0.12	0.15	0.20	99.47

Table 4 Crystallization temperatures of rutile

样品号	ZrO₂含量/%	t/℃
B1-Q1-Rt-1	0.30	879.00
B1-Q1-Rt-2	0.12	769.39
B1-Q1-Rt-3	0.09	740.43
B1-Q1-Rt-4	0.11	759.70
B1-Q1-Rt-5	0.14	789.32
B2042-Q4-Rt-3	0.11	763.20
B2042-Q4-Rt-4	0.11	761.68
B2042-Q5-Rt-1	0.16	803.76
B2042-Q5-Rt-2	0.17	808.74
B2042-Q5-Rt-4	0.12	771.63

Fig.9 δEu vs. Nb/Ta diagram of apatite

Fig.10 Hand specimen photographs of rocks and ores from the Oubulage porphyry copper-gold deposit a—Quartz porphyry with sulfide droplets; b—Ore with vesicles.

References 77

[1]	SINGER D A, BERGER V I, MENZIE W D, et al. Porphyry copper deposit density[J]. Economic Geology, 2005, 100(3): 491-514.
[2]	SILLITOE R H. Porphyry copper systems[J]. Economic Geology, 2010, 105(1): 3-41.
[3]	高俊, 朱明田, 王信水, 等. 中亚成矿域斑岩大规模成矿特征: 大地构造背景、流体作用与成矿深部动力学机制[J]. 地质学报, 2019, 93(1): 24-71.
[4]	HURTIG N C, MIGDISOV A A, WILLIAMS-JONES A E. Are vapor-like fluids viable ore fluids for Cu-Au-Mo porphyry ore formation?[J]. Economic Geology, 2021, 116(7): 1599-1624.
[5]	CALDER M F, CHANG Z S, ARRIBAS A, et al. High-grade copper and gold deposited during postpotassic chlorite-white mica-albite stage in the far southeast porphyry deposit, Philippines[J]. Economic Geology, 2022, 117(7): 1573-1596.
[6]	陈浩宇, 和文言. 岩浆演化过程中硫化物饱和对斑岩型Cu-Au矿床形成的控制[J]. 现代地质, 2024, 38(4): 947-958.
[7]	寇冠玉, 周晔, 郑远川, 等. 伊朗马斯杰德达吉(Masjed Daghi)始新世斑岩成因: 来自光谱学与U-Pb年代学和地球化学的证据[J]. 现代地质, 2021, 35(2): 535-551.
[8]	侯增谦. 斑岩Cu-Mo-Au矿床: 新认识与新进展[J]. 地学前缘, 2004, 11(1): 131-144.
[9]	侯增谦, 杨志明. 中国大陆环境斑岩型矿床: 基本地质特征、岩浆热液系统和成矿概念模型[J]. 地质学报, 2009, 83(12): 1779-1817.
[10]	TATNELL L, ANENBURG M, LOUCKS R. Porphyry copper deposit formation: identifying garnet and amphibole fractionation with REE pattern curvature modeling[J]. Geophysical Research Letters, 2023, 50(14): e2023GL103525.
[11]	张少颖, 和文言, 肖仪武. 镁铁质岩浆周期性补给对云南普朗斑岩Cu-Au矿床的制约: 能量约束下热力学模拟[J]. 现代地质, 2024, 38(4): 922-933.
[12]	MAO J W, ZHANG J D, PIRAJNO F, et al. Porphyry Cu-Au-Mo-epithermal Ag-Pb-Zn-distal hydrothermal Au deposits in the Dexing area, Jiangxi province, East China: a linked ore system[J]. Ore Geology Reviews, 2011, 43(1): 203-216.
[13]	ZHAI D G, WILLIAMS-JONES A E, LIU J J, et al. Mineralogical, fluid inclusion, and multiple isotope (H-O-S-Pb) constraints on the genesis of the sandaowanzi epithermal Au-Ag-Te deposit, NE China[J]. Economic Geology, 2018, 113(6): 1359-1382.
[14]	倪培, 迟哲, 潘君屹, 等. 热液矿床的成矿流体与成矿机制: 以中国若干典型矿床为例[J]. 矿物岩石地球化学通报, 2018, 37(3): 369-394, 560.
[15]	韩润生, 赵冻. 初论岩浆热液成矿系统控岩控矿构造深延格局研究方法[J]. 地学前缘, 2022, 29(5): 420-437.
[16]	罗照华, 卢欣祥, 郭少丰, 等. 透岩浆流体成矿体系[J]. 岩石学报, 2008, 24(12): 2669-2678.
[17]	罗照华. 流体-熔体强相互作用的成矿功能[J]. 矿物学报, 2011, 31(增刊1): 503-504.
[18]	BURET Y, VON QUADT A, HEINRICH C, et al. From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)[J]. Earth and Planetary Science Letters, 2016, 450: 120-131.
[19]	POLLARD P J, TAYLOR R G, PETERS L. Ages of intrusion, alteration, and mineralization at the grasberg Cu-Au deposit, Papua, Indonesia[J]. Economic Geology, 2005, 100(5): 1005-1020.
[20]	BALLARD J R, PALIN J M, CAMPBELL I H. Relative oxidation states of magmas inferred from Ce(IV)/Ce(III) in zircon: application to porphyry copper deposits of northern Chile[J]. Contributions to Mineralogy and Petrology, 2002, 144(3): 347-364.
[21]	PICCOLI P M, CANDELA P A. Apatite in igneous systems[J]. Reviews in Mineralogy and Geochemistry, 2002, 48(1): 255-292.
[22]	DING T, MA D S, LU J J, et al. Apatite in granitoids related to polymetallic mineral deposits in southeastern Hunan Province, Shi-Hang zone, China: implications for petrogenesis and metallogenesis[J]. Ore Geology Reviews, 2015, 69: 104-117.
[23]	PAN L C, HU R Z, WANG X S, et al. Apatite trace element and halogen compositions as petrogenetic-metallogenic indicators: examples from four granite plutons in the Sanjiang region, SW China[J]. Lithos, 2016, 254: 118-130.
[24]	陈雷, 闫臻, 王宗起, 等. 东秦岭160-140 Ma Cu(Mo)和Mo(W)矿床磷灰石成分特征[J]. 地质学报, 2017, 91(9): 1925-1941.
[25]	邢凯, 舒启海. 磷灰石在矿床学研究中的应用[J]. 矿床地质, 2021, 40(2): 189-205.
[26]	谭侯铭睿, 黄小文, 漆亮, 等. 磷灰石化学组成研究进展: 成岩成矿过程示踪及对矿产勘查的指示[J]. 岩石学报, 2022, 38(10): 3067-3087.
[27]	HUANG M L, ZHU J J, BI X W, et al. Low magmatic Cl contents in giant porphyry Cu deposits caused by early fluid exsolution:a case study of the Yulong belt and implication for exploration[J]. Ore Geology Reviews, 2022, 141: 104664.
[28]	李华伟, 杨志明. 岩浆锆石和磷灰石矿物化学及在斑岩矿床领域的应用[J]. 地质学报, 2023, 97(4): 973-1001.
[29]	李俊建, 骆辉, 陈安蜀, 等. 内蒙阿拉善地区成矿远景区划[J]. 矿床地质, 2002, 21(增刊1): 152-155.
[30]	李俊建, 翟裕生, 桑海清, 等. 内蒙古阿拉善欧布拉格铜-金矿床的成矿时代[J]. 矿物岩石地球化学通报, 2010, 29(4): 323-327
[31]	张勇. 内蒙古乌拉特后旗欧布拉格金铜矿地质特征及找矿方向[J]. 内蒙古科技与经济, 2015(3): 75-77.
[32]	SHEN P, PAN H D, HATTORI K, et al. Large Paleozoic and Mesozoic porphyry deposits in the Central Asian Orogenic Belt: geodynamic settings, magmatic sources, and genetic models[J]. Gondwana Research, 2018, 58: 161-194.
[33]	霍晓燕. 内蒙古欧布拉格铜金矿床的成矿特征与成矿机制[D]. 北京: 中国地质大学(北京), 2021.
[34]	吴晓蔓. 内蒙古欧布拉格铜金矿闪长玢岩成因及对成矿的指示意义[D]. 北京: 中国地质大学(北京), 2021.
[35]	邵积东, 王守光, 赵文涛, 等. 内蒙古北山: 阿拉善地区重要成矿带成矿地质特征及找矿潜力分析[J]. 西部资源, 2009(2): 53-55.
[36]	杨福新. 内蒙狼山地区构造地质演化及铀矿化分布格局的探讨[J]. 铀矿地质, 1994, 10(2): 78-86.
[37]	杨崇文, 任太平, 杨崇美. 内蒙古阿拉善铜-金矿床的地质地球化学特征[J]. 科技传播, 2011, 3(24): 91, 96.
[38]	SUN S S, MCDONOUGH W 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.
[39]	LIU M Y, ZHOU M F, SU S G, et al. Contrasting geochemistry of apatite from peridotites and sulfide ores of the Jinchuan Ni-Cu sulfide deposit, NW China[J]. Economic Geology, 2021, 116(5): 1073-1092.
[40]	YAO C L, LU J J, GUO W M. Compositional differencce between three generation of apatite from Tongchang porphyry deposit, Jiangxi Province, Southeast China[J]. Acta Mineralogica Sinica, 2007, 27(1): 31-40.
[41]	邓华兴. 磷灰石的阴极射线发光研究[J]. 地球化学, 1980, 9(4): 368-374.
[42]	WAYCHUNAS G A. Apatite luminescence[J]. Reviews inMineralogy and Geochemistry, 2002, 48(1): 701-742.
[43]	周瑶琪, 史冰洁, 李素, 等. 副矿物地球化学研究进展[J]. 中国石油大学学报(自然科学版), 2013, 37(4): 59-70.
[44]	BOUZARI F, HART C J R, BISSIG T, et al. Hydrothermal alteration revealed by apatite luminescence and chemistry: a potential indicator mineral for exploring covered porphyry copper deposits[J]. Economic Geology, 2016, 111(6): 1397-1410.
[45]	苏尚国, 崔晓亮, 罗照华, 等. 流体晶、流体晶矿物组合、流体岩及其研究意义[J]. 地学前缘, 2018, 25(6): 283-289.
[46]	罗照华. 流体地球科学与地球系统科学[J]. 地学前缘, 2018, 25(6): 277-282.
[47]	BELOUSOVA E A, WALTERS S, GRIFFIN W L, et al. Trace-element signatures of apatites in granitoids from the Mt Isa Inlier, northwestern Queensland[J]. Australian Journal of Earth Sciences, 2001, 48(4): 603-619.
[48]	CHU M F, WANG K L, GRIFFIN W L, et al. Apatitecomposition: tracing petrogenetic processes in transhimalayan granitoids[J]. Journal of Petrology, 2009, 50(10): 1829-1855.
[49]	ZHANG X B, GUO F, ZHANG B, et al. Magmatic evolution and post-crystallization hydrothermal activity in the Early Cretaceous Pingtan intrusive complex, SE China: records from apatite geochemistry[J]. Contributions to Mineralogy and Petrology, 2020, 175(4): 35.
[50]	张晓兵, 郭锋, 张博. 福建漳州花岗闪长岩成因: 来自磷灰石地球化学的约束[J]. 地球化学, 2022, 51(5): 585-597.
[51]	王启博, 张寿庭, 唐利, 等. 豫西杨山萤石矿床成因: 萤石稀土元素组成和流体包裹体热力学制约[J]. 现代地质, 2023, 37(6): 1524-1537.
[52]	CAO M J, LI G M, QIN K Z, et al. Major and trace element characteristics of apatites in granitoids from central Kazakhstan: implications for petrogenesis and mineralization[J]. Resource Geology, 2012, 62(1): 63-83.
[53]	MILES A J, GRAHAM C M, HAWKESWORTH C J, et al. Apatite:a new redox proxy for silicic magmas?[J]. Geochimica et Cosmochimica Acta, 2014, 132: 101-119.
[54]	邢凯, 舒启海, 赵鹤森, 等. 滇西普朗斑岩铜矿床中磷灰石的地球化学特征及其地质意义[J]. 岩石学报, 2018, 34(5): 1427-1440.
[55]	SHANNON R D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides[J]. Acta Crystallographica Section A, 1976, 32(5): 751-767.
[56]	BELOUSOVA E A, GRIFFIN W L, O’REILLY S Y, et al. Apatite as an indicator mineral for mineral exploration: trace-element compositions and their relationship to host rock type[J]. Journal of Geochemical Exploration, 2002, 76(1): 45-69.
[57]	SUN S J, YANG X Y, WANG G J, et al. In situ elemental and Sr-O isotopic studies on apatite from the Xu-Huai intrusion at the southern margin of the North China Craton: implications for petrogenesis and metallogeny[J]. Chemical Geology, 2019, 510: 200-214.
[58]	左琼华, 王伟, 王天华, 等. 云南镇康地区铅锌多金属矿成矿规律[J]. 地质找矿论丛, 2016, 31(4): 496-505.
[59]	MEINHOLD G. Rutile and its applications in earth sciences[J]. Earth-Science Reviews, 2010, 102(1/2): 1-28.
[60]	陶克勤, 闫峻, 李超, 等. 皖东蚌埠—五河地区重晶石石英脉中金红石特征与成因[J]. 矿物学报, 2023, 43(2): 201-214.
[61]	高晓英, 郑永飞. 金红石Zr和锆石Ti含量地质温度计[J]. 岩石学报, 2011, 27(2): 417-432.
[62]	孙紫坚, 方维萱, 鲁佳, 等. 云南因民铁铜矿区辉长岩类中黑云母-金红石化特征及其指示意义[J]. 现代地质, 2017, 31(2): 267-277.
[63]	ZACK T, MORAES R, KRONZ A. Temperature dependence of Zr in rutile: empirical calibration of a rutile thermometer[J]. Contributions to Mineralogy and Petrology, 2004, 148(4): 471-488.
[64]	WATSON E B, WARK D A, THOMAS J B. Crystallization thermometers for zircon and rutile[J]. Contributions to Mineralogy and Petrology, 2006, 151(4): 413-433.
[65]	CHEN X, SU S, SANTOSH M, et al. The role of fluid overpressure in Cu-Au porphyry mineralization: evidence from the Oubulage deposit, Inner Mongolia, China[J]. Geochemistry, 2025, 85(1):126258.
[66]	SHEN A H, KEPPLER H. Direct observation of complete miscibility in the albite-H₂O system[J]. Nature, 1997, 385(6618): 710-712.
[67]	倪怀玮. 超临界地质流体的性质和效应[J]. 矿物岩石地球化学通报, 2020, 39(3): 443-447, 440.
[68]	倪怀玮. 超临界地质流体研究进展简介[J]. 中国科学: 地球科学, 2023, 53(10): 2430-2433.
[69]	OHMOTO H. Stable isotope geochemistry of ore deposits[J]. Review in Mineralogy and Geochemistry, 1986, 16(1): 491-559.
[70]	王中良, 林木森, 周瑞辉. 滇东南荒田钨矿床白钨矿原位U-Pb年代学、 Sr同位素组成及成矿启示[J]. 现代地质, 2025, 39(1): 133-145.
[71]	王佳新, 焦建刚, 马云飞, 等. 内蒙古中部乌兰陶勒盖铜镍矿床形成时代与岩浆源区[J]. 现代地质, 2024, 38(4): 991-1012.
[72]	ZHANG Y, XUE S, SU S, et al. Timing of S-saturation in the formation of the Oubulage porphyry Cu-Au deposit, Inner Mongolia, Northern China[J]. Journal of Asian Earth Sciences, 2025, 280:106399.
[73]	疏孙平, 李秋根, 刘树文, 等. 斑岩型铜、金、钼矿床成岩成矿特征差异的原因和意义[J]. 地学前缘, 2018, 25(5): 237-250.
[74]	侯增谦, 杨志明, 王瑞, 等. 再论中国大陆斑岩Cu-Mo-Au矿床成矿作用[J]. 地学前缘, 2020, 27(2): 20-44.
[75]	杨志明, 侯增谦. 初论碰撞造山环境斑岩铜矿成矿模型[J]. 矿床地质, 2009, 28(5): 515-538.
[76]	WILKINSON J J. Triggers for the formation of porphyry ore deposits in magmatic arcs[J]. Nature Geoscience, 2013, 6(11): 917-925.
[77]	於崇文. 固体地球系统的复杂性与自组织临界性[J]. 地学前缘, 1998, 5(3): 347-368.