Iron Polymetallic Deposit Research Articles

Fine interpretation of magnetic data for a concealed mineral deposit: A case study of the Fe-polymetallic deposit from Western China

We interpret the magnetic anomalies for exploration and characterization of the Galinge iron polymetallic deposit, which is the largest iron polymetallic deposit in Western China. This undeveloped deposit is completely concealed by the thick Quaternary sediments, presenting an exploration challenge. A lot of drillholes have been implemented focusing on the strong magnetic anomaly centers, while the relationship between magnetite-bearing and non-magnetite-bearing drillholes is unclear, and the metallogenic regularity in the whole area needs to be further studied. The edge detection is applied on the downward continued field to resolve individual magnetite ore bodies and enhance possible concealed ore bodies. Three anomaly belts trending NE-SW with a total extension length of ∼11 km are first revealed. Combining the sharper images from the enhanced magnetic anomaly and the drillholes, we infer that the deposits would be related to the syncline structure. Forward modeling confirms the inferred three belts of the ore bodies and also shows possibly two layers deposits in which the deep layer would be located at a depth of ∼1000 m. Although the deeper deposit results in a very smooth and low amplitude magnetic anomaly, the forward modeling shows that the anomalies from both the shallow magnetite and the inferred deep one fit the observed anomaly better. One deep drillhole reveals the fact that the magnetite is existed at a depth of ∼1000 m which highlights the interpretation of the deep deposit. The results show the contribution of the fine processing techniques which would be used to distinguish zones of potentially concealed mineralization.

The Geochemical Characteristics of Trace Elements in the Magnetite and Fe Isotope Geochemistry of the Makeng Iron Deposit in Southwest Fujian and Their Significance in Ore Genesis

The Makeng iron deposit in southwest Fujian is a significant iron polymetallic deposit containing various types of iron ore, including garnet magnetite, diopside magnetite, and quartz magnetite. The metallogenetic type of the deposit has been a subject of debate, particularly in relation to the genesis of magnetite and the source of iron. In situ microanalysis of trace elements in magnetite from different ores shows relatively low levels of V, Ti, Cu, and Zn, with higher concentrations of Ca and Si, indicating the characteristics of a skarn type deposit. The δ57Fe values of the magnetite range from −0.091‰ to 0.317‰. Combining these data, whole-rock iron isotope analyses, including Juzhou and Dayang granites, diabase, and the Lower Carboniferous Lindi Formation sandstone, suggest that Fe in the magnetite primarily originates from granitic pluton, with potential contributions from diabase and the Lower Carboniferous Lindi Formation sandstone. Combined with field work, these results indicate that Makeng iron deposit is a skarn-type magnetite deposit associated with Yanshanian granitic intrusions. Therefore, the initial ore-forming fluid is postulated to be a high-temperature magmatic hydrothermal fluid with high oxygen fugacity. This fluid infiltrates spaces such as interlayer fracture zones between the Upper Carboniferous Jingshe Formation–Middle Permian Qixia Formation carbonate rocks and the Lower Carboniferous Lindi Formation sandstone, resulting in diverse magnetite ores due to metasomatism. The mineralization process of the Makeng iron deposit is basically the same, as it is composed of typical skarn deposits. Magnetite was mainly formed during calcic skarn formation stage, and this process persisted until the initial phase of the retrograde alteration of skarns. In contrast, sulfide minerals, including molybdenite, sphalerite, and galena, precipitated during the quartz–sulfide stage.

Geochemistry and Geochronology of the Gebunongba Iron Polymetallic Deposit in the Gangdese Belt, Tibet

The Gebunongba iron polymetallic deposit is a typical skarn deposit located at the westernmost end of the discovered iron polymetallic deposits in the Gangdese metallogenic belt. Major and trace elements of the monzonite granite related to mineralization show that these rocks are peraluminous (ACNK=1.15-1.21) and are rich in Si (76.63 wt.%-76.93 wt.% SiO2), K (K2O/Na2O ratio of 1.80-2.30), LREE and LILEs (Rb, Ba, Th, U, Pb), but is depleted in high field strength elements (Nb, Ta, Ti and HREE). In addition, these rocks show obviously negative Eu anomalies (δEu=0.48-0.55). The LA-ICPMS U-Pb age of zircons in monzonite granite is 59.72±0.55 Ma (MSWD=0.79), whereas the 40Ar/39Ar age of muscovite in iron ores is 59.22±0.61 Ma (MSWD=16.20). This indicates that the deposit formed at the syn-collision stage of Lhasa-India terrane is later than the northward subduction of the Yajiang crust. The monzonite granite has been probably derived from the partial melting of ancient lower crustal materials, which is probably resulted from the underplating of mantle-derived magmas. It is favorable for the formation of iron polymetallic deposit. Iron polymetallic mineralization is prevalent in Gangdese metallogenic belt at syn-collision stage. Therefore, syn-collision stage is an important mineralization stage for iron polymetallic deposits. The results of this study proved that iron polymetallic mineralization still took place in the western segment of Gangdese metallogenic belt and provided basis for further prospecting the deposits of the same type.

Garnet composition as an indicator of skarn formation: LA‐ICP‐MS and EPMA studies on oscillatory zoned garnets from the Haobugao skarn deposit, Inner Mongolia, China

Oscillatory zoned garnets are widespread in the Haobugao skarn‐type copper–lead–zinc–iron polymetallic deposit, and they can record garnet growing process in the early stages of metallogenesis. In order to investigate the skarn‐forming process and hydrothermal fluid evolution of the Haobugao deposit, major, trace, and rare earth element (REE) contents of oscillatory zoned garnets were analysed by electron probe microscope analysis (EPMA) and laser‐ablation inductively‐coupled plasma mass spectrometry (LA‐ICP‐MS) techniques. Three distinct generations of garnets were identified: the first generation garnets (Grt I) are Fe‐rich, euhedral, fine‐ to coarse‐grained, isotropic, show characteristic concentric oscillatory zoning, and have light rare earth element (LREE)‐enriched and heavy rare earth element (HREE)‐depleted REE patterns, with strong positive Eu anomalies and low ΣREE concentrations. The second generation garnets (Grt II) are Al‐rich, anhedral to subhedral, anisotropic, with abundant oscillatory zoning alone the growth lines, and have LREE‐depleted and HREE‐enriched REE patterns, with negligible Eu anomalies and relatively higher ΣREE concentrations. The third generation garnets (Grt III) are anhedral, anisotropic and generally occurred at the rim of pre‐existing Grt I or beside fractures that cut through the pre‐existing Grt I crystals. All these three generations garnets show oscillatory zoning under an optical microscope and have different compositions from each other, but there's limited chemical zoning (such as bell‐shaped zoning of major elements) in each individual garnet crystal.The texture and composition characteristics of the garnets indicate that the Grt I is precipitated rapidly from high temperature and oxidized magmatic fluids by advective metasomatism, in a high water/rock ratio condition; the Grt II is precipitated from low temperature residual fluids that were in equilibrium with the host rock by diffusive metasomatism, in a low water/rock ratio condition; and the Grt III is formed by retrograde hydrothermal‐metasomatic alteration of pre‐existing garnets. The incorporation of REE into garnet is controlled by its crystal chemistry and fluid composition, dominated by the YAG (yttrium aluminium garnet) ‐type substitution mechanism .

The research on ore-controlling factors of Haxiyatu iron-polymetallic deposit of East Kunlun

Haxiyatu iron-polymetallic deposit of East Kunlun is located in Qimantage met allogenic belt, the main met allogenic elements are iron, copper, lead, zinc, gold, etc. Based on the geological characteristics and mineralization of ore deposits, this paper concluded that, firstly the brittle contact zone of Jinshuikou rock group and carbonate rock provided a good space for mineralization, secondly the deep minor fractures caused by the regional fracture provided the transport channel for the material. At last, the quartz diorite originated from the mixed source of crust-mantle in the mining area provided a material basis for the mineralization.

Zircon U-Pb geochronology, geochemistry, and S-Pb isotopic compositions of the Lietinggang iron polymetallic deposit, Tibet, China

The Lietinggang deposit is a representative skarn iron polymetallic deposit in the Nyainqêntanglha skarn polymetallic zone (NSP) in Lhasa Terrane, Tibet. The mineralization is hosted in skarn of the Early and Middle Triassic Chaqupu Formation. Plutons in the deposit include gabbro, diorites (divided into the D1 and D2 diorites), granodiorite, syenogranite and porphyritic granite, and the D2 diorite and syenogranite are the mineralization associated plutons. In this study, we present LA-ICP-MS zircon U-Pb dating, zircon Hf isotopic and whole rock geochemical data of the diorites and porphyritic granite and S-Pb isotopic compositions of the ore sulfides in the Lietinggang deposit. Zircon U-Pb dating results for these intrusions yield Paleocene ages of 62.2–59.0 Ma. All the intermediate and felsic intrusions are I-type, and characterized by arc magma geochemical features, enriched in LREE and LILE, well developed negative Eu anomalies and depletion in HFSE, with most having positive εHf(t) values. These geochemical characteristics are similar with the coeval intrusions of the Gangdese batholith and Linzizong Group volcanic rocks, indicating they share a similar magma source. This magma source is proposed to be partial melting of the young metasomatized asthenospheric mantle wedge-derived basaltic rocks. During the magma evolution the fractionated crystallization has also play an important role. δ34S values for sulfides have features of magma source. The 206Pb/204Pb (18.043–18.711), 207Pb/204Pb (15.520–15.776), and 208Pb/204Pb (38.288–39.215) values of sulfides show that ore-forming metals were derived from mixing sources of mantle with upper crust materials. Geochemical characteristics of the intermediate and felsic intrusions, combined with the dating results, indicate that the Lietinggang magmatism and mineralization were formed within the India-Asia continental-collision tectonic setting.

The research on the characteristics of skarn alteration zones in Haxiyatu iron-polymetallic deposit of East Kunlun

Haxiyatu iron-polymetallic deposit in Qinghai East Kunlun is a typical regional strata bound skarn ore deposits, the major ore-host rock is Jinshuikou rock group and the metallogenic epoch is the early Triassic. This paper studied the amphibole, epidote, garnet and pyroxene, garnet and petrographic of Haxiyatu skarn deposit, divided the deposit alteration zoning characteristics in detail, and according to the mineral assemblages and skarn deposit mineral sequence, figured out three formation periods, including the skarn deposit stage, degenerate alteration stage and metal sulfide stage.

The relationship between magma and mineralization in Chaobuleng iron polymetallic deposit, Inner Mongolia

The Chaobuleng iron polymetallic deposit, an important ore system in China that is genetically related to the early Cretaceous Chaobuleng pluton, is located in the eastern part of Lizi Shan-Dong Ujimqin Banner metallogenic belt of Inner Mongolia. To understand the relationship of magmatism and mineralization in this iron polymetallic deposit, we have conducted a detailed geologic field study in conjunction with systematic investigation of U-Pb zircon and Re-Os isochron geochronology, mineralogy, petrology, major-and trace-element geochemistry, and synthesis of existing datasets across the Chaobuleng region. We use these observations to identify the origins and petrogenesis of mafic enclaves and the host granitoid, and to place new constraints on the tectonic setting at the time of magmatism. New U-Pb geochronology of magmatic zircons and Re–Os isochron ages of hydrothermal molybdenite from the iron polymetallic deposit allow us to constrain the sources of the hydrothermal components and the relationship between iron polymetallic mineralization and regional geodynamic evolution. The geology, paragenesis, and estimated P-T conditions suggest that the Chaobuleng iron polymetallic deposit was formed as a shallow, proximal skarn deposit. The ore-forming early Cretaceous Chaobuleng pluton can be divided into three distinct units based on crystallization age, texture, and composition: (1) a 138.1–140.6Ma syenogranite porphyry, (2) a 137.4–138.6Ma enclave bearing porphyritic syenogranite, and (3) a 133.9–135.98Ma coarse-grained porphyritic syenogranite. We suggest that the A-type Chaobuleng pluton was formed in a post-orogenic extensional setting with significant magma mixing from high-temperature melts (i.e., a Zr saturation temperature of 800–900°C). During the magmatic process, the Chaobuleng pluton crystallized under temperatures as low as 720–770°C and pressures of 0.5–1.0kbar. The chemical composition of biotite shows that the Chaobuleng magma was enriched in F (1.5–3.5%). We attribute the observed embayed texture of quartz to a three coexisting-phase equilibrium model that operated during the magmatic-hydrothermal transition and can be used to constrain the mineralization process and physico-chemical conditions. Due to a loss of volatiles, the residual melt was quickly quenched and crystallized into a fine-grained groundmass. The Re–Os model ages of samples from the inner pluton-mineralization contact belt are 135.0±2.1Ma and 131.2±4.1Ma, and a sample from the outer-contact belt yields an isochron age of 140.7±1.8Ma. The Chaobuleng deposit formed during protracted activity of the magmatic-hydrothermal system, which is similar to many mineralization systems around the world. However, the major mineralization stage (iron oxide stage) of the Chaobuleng deposit occurred during the early stage of magmatism, consistent with the emplacement time of syenogranite porphyry at ~139Ma.

Genetic relationship between unroofing of the Emeishan large igneous province and the iron-polymetallic deposit in western Guizhou, Southwestern China: Constraint from U-Pb geochronology and geochemistry of zircon

报道了对位于黔西六盘水-威宁地区铁-多金属矿床开展的锆石U-Pb年代学和微区元素地球化学研究, 揭示了该新型矿床的成因与峨眉山大火成岩省的去顶作用有关. 通过分析和总结峨眉山大火成岩省边缘地区不同类型表生矿床的空间分布特征, 本研究提出该矿床成因是特殊的古地理环境(形成富铁红土化剖面)与晚二叠世时期反复的海进和海退作用相耦合的产物.

Oxygen, Sulfur and Lead Isotopic Compositions and Sources of the Ore Metals of Dapai Iron Polymetallic Deposit in Southwestern Fujian Province

Oxygen, Sulfur and Lead Isotopic Compositions and Sources of the Ore Metals of Dapai Iron Polymetallic Deposit in Southwestern Fujian Province