Geology, Geochronology, and Geochemistry of the Dahongshan Fe-Cu-(Au-Ag) Deposit, Southwest China: Implications for the Formation of Iron Oxide Copper-Gold Deposits in Intracratonic Rift Settings
Geology, Geochronology, and Geochemistry of the Dahongshan Fe-Cu-(Au-Ag) Deposit, Southwest China: Implications for the Formation of Iron Oxide Copper-Gold Deposits in Intracratonic Rift Settings
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中国西南大红山铁铜（金银）矿床的地质、年代学和地球化学：对克拉通内裂谷环境中氧化铁铜金矿床形成的启示
DOI：
10.2113/econgeo.112.3.603
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发表时间：
2017-05
期刊：
影响因子：
--
通讯作者：
Li Jian-Wei
中科院分区：
文献类型：
--
作者：
Zhao Xin-Fu;Zhou Mei-Fu;Su Zhi-Kun;Li Xiao-Chun;Chen Wei-Terry;Li Jian-Wei
大红山大型铁-铜-(金-银)矿床位于中国西南铁氧化物铜金成矿省，矿石含铁41.0%，含铜1.35Mt，含铁41.0%，含金16t，含银141t，含钴18156t，含Pd+铂2.1t，矿石质量分数约458.3 Mt。矿床主要由两类矿石组成：(1)赋存于广泛钠交代的变质火山岩、变质砂岩和角砾岩中的块状或条带磁铁矿(赤铁矿)透镜；(2)云母片岩和大理岩中的层控浸染、网状和条带磁铁矿-黄铜矿-(斑铜矿)。这两类矿体和围岩都经历了广泛的热液蚀变，形成了类似的共生作用。侵入阶段I，钠长蚀变形成广泛的钠长石和局部的方沸石。随后被以阳起石、钾长石、黑云母、绢云母和绿泥石为代表的富钙或富钾矿物交代。磁铁矿略年轻于钠长石蚀变组合，并与钠盐质蚀变组合部分重叠。赤铁矿在结构上晚于磁铁矿，在块状氧化铁矿体中局部丰富，并与绢云母密切相关。三期铜硫化物与石英、黑云母、绢云母、绿泥石等矿物共生。阶段II和阶段III分别以广泛分布的菱铁矿和铁白铁矿为主。石英-方解石脉标志着第IV期热液蚀变减弱的结果。除了在主要成矿事件期间广泛的蚀变外，在矿后岩浆和变质事件期间，该矿床还经历了广泛的叠加和再活化。大红山矿体与丰富的辉绿岩脉和岩床密切相关，它们的热液矿物组合与赋矿岩石中的相似。切割块状铁矿体的一块辉绿岩床的激光烧蚀-等离子体质谱锆石U-Pb年龄为1661±7 Ma，与网状黄铜矿-磁铁矿中热液锆石的年龄1653±18 Ma一致。因此，锆石U-Pb年龄被认为标志着形成大红山矿床的主要矿化的时代。不协调石英-碳酸盐-硫化物矿脉中黄铁矿的Re-Os等时线年龄为1026±22 Ma，辉钼矿的Re-Os同位素年龄为830 Ma左右。前者与本区晚中元古代岩浆活动同时代，后者与中国西南地区新元古代区域性变质事件同时代。钠长石化大理岩的碳、氧同位素值介于地幔岩浆碳和白云岩端元之间。与II期磁铁矿平衡的成矿流体的δ18 O值为9.1~9.5‰，而与石英和铁闪石沉积有关的流体的δ18 O值较低，为2.9~7.3‰。氧同位素数据表明，与II期有关的成矿流体在III、IV期主要来自岩浆，并与丰富的盆地卤水混合，这一解释与矿床中硫化物的硫同位素值一致。大红山黄铁矿和黄铜矿的δ34 S值在−3.4~+12 4‰范围内变化很大，表明沉积岩中存在岩浆硫和外部硫(可能来自盆地卤水)的混合。大红山矿床形成于克拉通内裂谷环境，是由于基性岩浆的底侵作用导致围岩中大规模的流体循环和普遍的钠钙交代作用。矿石金属主要来自深部岩浆房，部分来自围岩。由于成矿流体施加的超压，围岩的热液角砾化形成于辉绿岩侵入岩的顶部和围岩内的薄弱地带。磁铁矿和赤铁矿在辉绿岩侵入岩附近较早沉淀，而铜硫化物较晚在硫化物饱和的围岩中形成。我们认为，这种成因模式可能广泛适用于其他地区形成于克拉通内裂谷环境的前寒武纪IOCG矿床。
The large Dahongshan Fe-Cu-(Au-Ag) deposit in the Kangdian iron oxide copper-gold (IOCG) metallogenic province, southwest China, contains approximately 458.3 Mt of ore at 41.0% Fe, 1.35 Mt Cu (metal) at 0.78% Cu, and significant amounts of Au (16 t), Ag (141 t), Co (18,156 t), and Pd + Pt (2.1 t). The deposit consists mainly of two types of ores: (1) lenses of massive or banded magnetite-(hematite) hosted in extensively Na metasomatized metavolcanic rocks, metaarenite, and brecciated rocks, and (2) strata-bound disseminated, stockwork, and banded magnetite-chalcopyrite-(bornite) in mica schist and marble. Both types of orebodies and country rocks underwent extensive hydrothermal alteration, resulting in a similar paragenesis. Pervasive stage I sodic alteration formed widespread albite and local scapolite. It was subsequently replaced by Ca- or K-rich minerals represented by actinolite, K-feldspar, biotite, sericite, and chlorite of stages II and III. Magnetite is slightly younger than and partly overlaps the sodic alteration assemblages. Hematite is texturally later than magnetite, is locally abundant within the massive Fe oxide orebody, and is closely associated with sericite. Copper sulfides are coeval with quartz, biotite, sericite, and chlorite in stage III assemblages. Widespread siderite and ankerite predominate in stages II and III, respectively. Quartz-calcite veins mark the result of waning stage IV hydrothermal alteration. In addition to widespread alteration during the major ore-forming event, the deposit has also undergone extensive overprinting and remobilization during post-ore magmatic and metamorphic events. The Dahongshan orebodies are intimately associated with abundant doleritic dikes and sills that have hydrothermal mineral assemblages similar to those in the ore-hosting rocks. One dolerite sill that cuts a massive Fe orebody has a laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb age of 1661 ± 7 Ma, which is, within uncertainty, consistent with the age of 1653 ± 18 Ma determined for hydrothermal zircons from stockwork chalcopyrite-magnetite ore. The zircon U-Pb ages are thus considered to mark the timing of major mineralization that formed the Dahongshan deposit. Post-ore modification is recorded by an Re-Os isochron age of 1026 ± 22 Ma for pyrite in discordant quartz-carbonate-sulfide veins, and by younger Neoproterozoic mineralization dated at ca. 830 Ma using Re-Os isotopes on molybdenite. The former age is contemporaneous with late Mesoproterozoic magmatism in the region, whereas the latter is coeval with regional Neoproterozoic metamorphic events in southwest China. Carbon and oxygen isotope values of albitized marble are between those of mantle-derived magmatic carbon and dolostone end members. The ore-forming fluids that equilibrated with stage II magnetite have δ 18 O values of 9.1 to 9.5‰, whereas fluids linked to the deposition of quartz and ankerite during stages III and IV have lower δ 18 O values of 2.9 to 7.3‰. The oxygen isotope data indicate that the ore-forming fluids related to stage II are chiefly magmatically derived and mixed with abundant basinal brine during stages III and IV; this interpretation is consistent with sulfur isotope values of sulfides in the deposits. Pyrite and chalcopyrite from the Dahongshan deposit have a large range of δ 34 S values from −3.4 to +12.4‰, implying mixing of magmatic and external sulfur (likely from basinal brines) in sedimentary rocks. The Dahongshan deposit formed in an intracratonic rift setting due to underplating by mafic magmas that induced large-scale fluid circulation and pervasive sodic-calcic metasomatism in country rocks. Ore metals were derived mainly from a deep-seated magma chamber and partly from country rocks. Hydrothermal brecciation of the country rocks formed at the top of the dolerite intrusions and along zones of weakness within the country rocks owing to overpressure imposed by the ore fluids. Magnetite and hematite precipitated early near the dolerite intrusions, whereas Cu sulfides formed later in country rocks where sulfide saturation was favored. We propose that this genetic model may be widely applicable to Precambrian IOCG deposits elsewhere that formed in intracratonic rift settings.
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影响因子：
3.8
作者：
Kendrick, M. A.;Baker, T.;Williams, P. J.
通讯作者：
Williams, P. J.
影响因子：
--
作者：
Chuan-heng Zhang;Linzhi Gao;Zhenjie Wu;Xiaoying Shi;Q. Yan;Dajian Li
通讯作者：
Chuan-heng Zhang;Linzhi Gao;Zhenjie Wu;Xiaoying Shi;Q. Yan;Dajian Li
古元古代岩浆和变质事件将长江与努纳超大陆劳伦大陆西北部连接起来
影响因子：
5.3
作者：
Wang, Wei;Cawood, Peter A.;Zhou, Mei-Fu;Zhao, Jun-Hong
通讯作者：
Zhao, Jun-Hong
影响因子：
5.8
作者：
Chen, Huayong;Clark, Alan H.;Moody, Timothy C.
通讯作者：
Moody, Timothy C.
影响因子：
3.9
作者：
Martin P. Smith;C. Storey;T. Jeffries;C. Ryan
通讯作者：
Martin P. Smith;C. Storey;T. Jeffries;C. Ryan