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... Kaerqueka, Wulanwuzhuer, and Yazigou ( Figure 1b); Fe skarn deposits occur in Yemaquan, Galinge, and Kendekeke, whereas Pb-Zn skarn deposits are found in Weibao, Sijiaoyang, and Niukutou. Furthermore, small deposits and mines are scattered throughout the region, a fact that has attracted the attention of many researchers [7][8][9][10][11]. Published studies have shown that the skarn mineralization in this area is genetically related to Triassic granitoids [12,13] and that different deposits are generally characterized by a distinct skarn mineral composition. ...
... Typical Cu (Mo) skarn deposits are found in Kaerqueka, Wulanwuzhuer, and Yazigou ( Figure 1b); Fe skarn deposits occur in Yemaquan, Galinge, and Kendekeke, whereas Pb-Zn skarn deposits are found in Weibao, Sijiaoyang, and Niukutou. Furthermore, small deposits and mines are scattered throughout the region, a fact that has attracted the attention of many researchers [7][8][9][10][11]. Published studies The Niukutou Pb-Zn skarn deposit is located in the eastern part of the QMB ( Figure 1b). ...
... content and low MgO (0.62%-11.53%) and MnO (0.99%-4.44%) contents. In terms of the components calculated by the johannsenite -hedenbergite-diopside end members [26], Px1 (Di 5-65 Hd 32-80 Jo [3][4][5][6][7][8][9][10][11][12][13][14][15] ) was largely composed of hedenbergite, with small amounts of diopside and johannsenite ( Figure 10). of the components calculated by the johannsenite-hedenbergite-diopside end members [26], Px1 (Di5-65Hd32-80Jo3-15) was largely composed of hedenbergite, with small amounts of diopside and johannsenite ( Figure 10). ...
The Niukutou Pb-Zn deposit is typical of skarn deposits in the Qimantagh metallogenic belt (QMB) in the East Kunlun Mountains. In this study, based on detailed petrographical observations, electron microprobe analyses (EMPAs), and laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analyses, we report the major and trace element compositions of the typical skarn mineral assemblages (garnet, pyroxene, ilvaite, epidote, and chlorite) in this deposit. Three hydrothermal mineralization stages with different mineral assemblages of the prograde metamorphic phase were determined, which were distributed from the inside to the outside of the ore-forming rock mass. Grt1+Px1 (Stage 1), Grt2+Px2 (Stage 2), and Px3 (Stage 3) were distinguished in the Niukutou deposit. Furthermore, the ilvaites in the retrograde metamorphic phase can be divided into three stages, namely Ilv1, Ilv2, and Ilv3. The ore-forming fluid in Stage 1 exhibited high ∑REE, U, and Nd concentrations and δEu, δCe, and LREE/HREE values, which were likely derived from a magmatic–hydrothermal source and formed at high temperatures, high fO2 values, and mildly acidic pH conditions, and probably experienced diffusive metasomatism in a closed system with low water/rock ratios. In Stages 2 and 3, the ore-forming exhibited lower ∑REE, U, and Nd concentrations and δEu, δCe, and LREE/HREE values, with high Mn content that had likely experienced infiltrative metasomatism in an open system with high water/rock ratios. From Ilv1 to Ilv3, the δEu and U contents decreased, whereas the Mn content increased, indicating that the oxygen fugacity of mineralization was in decline. The ore-forming fluid evolution of the Niukutou deposit can be characterized as follows: from Stage 1 to Stage 3, the hydrothermal fluid migrated from the deep plutons to the shallow skarn and marble; the environment altered from the high fO2 and temperature conditions to low fO2 and temperature values, and the pH and Mn contents increased. The fluids contained considerable metal ore-forming materials that were favorable for the enrichment and precipitation of the Fe content. In the retrograde metamorphic phase, with the decrease in oxygen fugacity (from Ilv1 to Ilv3), the temperature and oxygen fugacity of the theore-forming fluid environment decreased, ultimately becoming conducive to the dissolution and precipitation of Pb and Zn elements.
... Therefore, a corrected and appropriate mineral deposit model or exploration targeting model is of vital importance to carry out prediction for mineral resource prospectivity . Past researchers believed that the Fe mineralization in the SFMB was due to the marine sedimentary mechanism (Chen, 2002; Lin, 2008) or the marine volcanic sedimentary and hydrothermal re-working mechanism (Ge et al., 1981; Wang et al., 1981; Zhu et al., 1982; Han and Ge, 1983; Chen et al., 1985; Jiang, 2009); however, recent studies have suggested that these deposits are in fact skarn-type deposits associated with the Yanshanian granitoids (Zhao et al., 1983; Chen, 2010; Zhang, 2012; Zhang et al., 2012a Zhang et al., , 2012b Zhang et al., , 2012c Yuan et al., 2013; Zuo, 2013, 2014; Lai et al., 2014; Zhang et al., 2015a Zhang et al., , 2015b). Zuo et al. (2015) proposed a predictive model with four key geological features, including Yanshanian granites, faults, Carboniferous-Permian carbonate formations, and geochemical anomalies; they obtained a relatively good predictive result using a modified fuzzy weights of evidence model (). ...
... Recent studies have proved that the widespread iron deposits in the SFMB are skarn-type deposits associated with the Yanshanian granites (Zhao et al., 1983; Chen, 2010; Zhang, 2012; Zhang et al., 2012a Zhang et al., , 2012b Zhang et al., , 2012c Yuan et al., 2013; Zuo, 2013, 2014; Lai et al., 2014). There is still excellent potential for mineral exploration because large areas in this belt are covered by forest (Cheng, 2012). ...
Recent studies have pointed out that the widespread iron deposits in southwestern Fujian metallogenic belt (SFMB) (China) are skarn-type deposits associated with the Yanshanian granites. There is still excellent potential for mineral exploration because large areas in this belt are covered by forest. A new predictive model for mapping skarn-type Fe deposit prospectivity in this belt was developed and focused on in this study, using five criteria as evidence: (1) the contact zones of Yanshanian granites (GRANITE); (2) the contact zones within the late Paleozoic marine sedimentary rocks and the carbonate formations (FORMATION); (3) the NE-NNE-trending faults (FAULT); (4) the zones of skarn alterations (SKARN); and (5) the aeromagnetic anomaly (AEROMAGNETIC). The fuzzy weights of evidence (FWofE) method, developed from the classical weights of evidence (WofE) and based on fuzzy sets and fuzzy probabilities, could provide smaller variances and more accurate posterior probabilities and could effectively minimize the uncertainty caused by omitted or wrongly assigned data and be more flexible than the WofE. It is an efficient and widely used method for mineral potential mapping. Random forests (RF) is a new and useful method for data-driven predictive mapping of mineral prospectivity method, and needs further scrutiny. Both prospectivity results respectively using the FWofE and RF methods reveal that the prediction model for the skarn-type Fe deposits in the SFMB is successful and efficient. Both methods suggested that the GRANITE and FORMATION are the most valuable evidence maps, followed by SKARN, AEROMAGNETIC, and FAULT. This is coincident with the skarn-type Fe deposit mineral model in the SFMB. The unstable performance experienced when FORMATION was omitted might indicate that the highest uncertainty and risk in follow-up exploration is related to the sequences. In addition, the performance of the RF method for the skarn-type Fe deposits prospectivity in the SFMB is better than the FWofE; therefore, it could be used to guide further exploration of skarn-type Fe prospects in the SFMB. © 2015 Science China Press and Springer-Verlag Berlin Heidelberg
... The Makeng deposit, an ore reserve of more than 350 Mt with an average grade of 37.85 % total Fe, is one of the largest Fe deposits in Fujian Province and South China. Recent studies have suggested that the Makeng Fe deposit is a skarn-type deposit (Zhao et al. 1983;Chen 2010;Zhang 2012;Zhang et al. 2012a, b;Zhang andZuo 2013, 2014). Hercynian mafic intrusions, which have yielded an age of 303 ± 2 Ma via U-Pb dating of zircons using LA-ICP-MS (Zhang 2012), and Yanshanian (i.e., early Cretaceous) Dayang-Juzhou (DJ) granitic intrusion is intruded in the Makeng ore deposit district. ...
... Hercynian mafic intrusions, which have yielded an age of 303 ± 2 Ma via U-Pb dating of zircons using LA-ICP-MS (Zhang 2012), and Yanshanian (i.e., early Cretaceous) Dayang-Juzhou (DJ) granitic intrusion is intruded in the Makeng ore deposit district. Hong et al. (1980) have reported an age of 95.5 Ma from K-feldspar Rb-Sr dating and a biotite K-Ar age of 124 ± 4 Ma for the DJ granite, 1 3 whereas two different biotite K-Ar ages of 112 and 156 Ma have been suggested by Zhao et al. (1983). Mao et al. (2006) also obtained two similar single zircon evaporation ages of 136 and 133.9 Ma, whereas an LA-ICP-MS U-Pb age of 129.6 ± 0.8 Ma and a Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb age of 132.6 ± 1.3 Ma have been reported for the DJ granite by Zhang et al. (2012b). ...
The Makeng Fe deposit is located in the southwestern Fujian district, South China. The Sm–Nd isochron ages of seven samples of pure garnet and five of pure magnetite separates from the Makeng ores yielded an isochron age of 157 ± 15 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating of the nearby exposed the Dayang–Juzhou (DJ) porphyritic biotite granite and fine-grained syenogranite yielded 206Pb/238U ages of 140.2 ± 1.1 and 140.1 ± 1.0 Ma, respectively. These results suggest that the intrusion of the DJ granite and the Makeng skarn alterations and Fe mineralization are contemporaneous. The DJ granite exhibits geochemical characteristics of A-type granites, including high values of Na2O + K2O (8.13–8.92 wt%), FeOt/MgO (3.4–21.5), and Ga/Al (2.64–3.45 × 10−4), and low Al2O3 (10.71–13.29 wt%) value. Chondrite-normalized rare earth element patterns are characterized by obviously negative Eu anomalies (δEu = 0.02–0.28) and primitive-mantle normalized spidergrams show the enrichment in high field strength element and depleting in Sr, Ti, Ba, and Eu. The geochemical characteristics of DJ granite suggest that the granite was derived from partial melting of the Paleoproterozoic metasedimentary rocks of the Cathaysia basement. And some underplating of mafic magma in the lower tholeiitic crust and/or depleted mantle might be involved and provide the heat source for the partial melting. The DJ granite also fits the spatiotemporal distribution of the Jurassic–Cretaceous coastward migration of both extensional and arc-related magmatism and fills the A-type granites gap in the early stage of the early Cretaceous (145–125 Ma). Therefore, it is suggested that the late Jurassic and early Cretaceous magmatism in southwestern Fujian district were generated in an extensional environment responding to the slab rollback and concomitant retreating arc system of the paleo-Pacific plate within the South China Block. And the Fe metallogeny in southwestern Fujian district is genetically linked with the magmatism during this period.
... (2) marine volcanic sedimentary and hydrothermal re-working (Chen et al., 1985;Ge et al., 1981;Han and Ge, 1983;Jiang, 2009;Wang et al., 1981;Zhu et al., 1982); and (3) skarn-type iron deposit (Chen, 2010;Zhang, 2012;Zhang et al., 2012a;Zhao et al., 1983;Zuo et al., 2012). These views differ primarily about the origin of the iron and the mineralizing fluids. ...
... The second viewpoint advocates that the iron originated from the eruption of submarine volcanoes and was enriched and deposited by the circulation of seawater and meteoric water (Chen et al., 1985;Ge et al., 1981;Han and Ge, 1983;Jiang, 2009;Wang et al., 1981;Zhu et al., 1982). However, other researchers (e.g., Chen, 2010;Zhang, 2012;Zhang et al., 2012a;Zhao et al., 1983) advocate a third viewpoint in which the iron would have been generated from magmas and the dominant fluids are magmatic, with a certain amount of seawater or meteoric water. ...
The Makeng Fe(− Mo) deposit is the largest Fe deposit in the southwestern Fujian depression belt in southern China. Although it has been extensively studied, there are different views on the genesis of the deposit. In the present study, Sr–Nd–Pb isotope data were used to determine the source of fluids and metals in the deposit. The initial 87Sr/86Sr and εNd (133 Ma) ratios of magnetite samples from Makeng ore vary from 0.71067 to 0.71267 and from − 11.2 to − 8.7, respectively. Ratios for granites vary from 0.70878 to 0.71349 and from − 11.2 to − 8.7, respectively. The magnetite samples yield narrow ranges for 206Pb/204Pb (18.405–18.926), 207Pb/204Pb (15.657–15.710), and 208Pb/204Pb (38.598–38.809). The granites show ranges from 18.787 to 19.154, 15.670 to 15.692 and 39.158 to 39.413 for the same Pb isotopic ratios, respectively. The isotopic data of magnetite and granites shows that the Sr–Nd–Pb isotopic characteristics of magnetite samples are similar to the granites. According to the Sr–Nd–Pb isotopic characteristics, O–H isotopic systematics and rare earth elements characteristics, the initial mineralizing fluids and metals probably originated from granite magmas involving materials from Hercynian diabases or intruded country rocks. Field and laboratory observations suggest that skarn alteration is widespread in the Makeng ore district, indicating that the Makeng Fe deposit is a skarn-type iron deposit.
... The Makeng deposit is one of the largest iron deposits in Fujian province and south China. Since its discovery, the mineralization of the Makeng Fe deposit has been widely studied; recent studies have proved that the Makeng Fe deposit is in fact a skarn-type deposit (Zhao et al., 1983; Chen, 2010; Zhang, 2012; Zhang et al., 2012a; Zhang & Zuo, 2013). However, because of the different periods of intrusions and their complex interpenetration relationships, the formation time of the skarns and Fe mineralization are still debatable. ...
Recent studies have revealed that the Makeng Fe deposit is a skarn type deposit. However, the skarns in Makeng, occurring primarily between limestone and sandstone, are not typically associated with limestone and plutons. Different periods of intrusions, e.7. Hercynian mafic intrusions and Yanshanian (i.e. early Cretaceous) Dayang–Juzhou granitic intrusion, occurred in the Makeng deposit district. In this study, the formation processes of the skarns and Fe mineralization are constrained by detailed fieldwork, petrology, geochronology, and geochemistry. Skarns and Fe mineralization intersecting the Hercynian mafic intrusions are observed in consecutive specimens from the 106# tunnel. They suggest that the skarn formation and Fe mineralization occurred after the Hercynian mafic intrusions and are related to the later Yanshanian Dayang–Juzhou granitic intrusion. The geochronological characteristics of weakly skarn-altered diabases, the decreasing nature of Fe contents in altered diabase, and the major element compositions of pyroxenes and garnets also support that Hercynian mafic intrusions are strongly reformed by Yanshanian granitic magmas and the Fe migrated from mafic intrusion was responsible for formation of iron ore.
... for skarn-related Fe deposition, some earlier researchers regard the Makeng deposit as a stratabound skarn Fe deposit (e.g., Zhao et al., 1983). In comparison, the curve related to the missing evidence for faults is closest to the x-axis, which shows that the prediction with missing evidence for faults is the best and that fault control on skarn Fe mineralization is less ...
In this paper, the southwestern Fujian metallogenic belt, one of the important Fe polymetallic belts in southern China, was chosen as a case study area to evaluate the uncertainty due to missing evidence in mineral prospectivity mapping. Four geological features were considered important for mineral prospectivity mapping based on the geological model for skarn deposits in the belt: (1) the Yanshanian granitic intrusions, because they provided energy, fluids, and part of the metal budget; (2) faults, because they served as pathways for hydrothermal fluids; (3) the Carboniferous–Permian carbonate sequences, because they supplied part of the metal budget and served as host rocks for ore deposition; and (4) geochemical anomalies, because they indicate presence of skarn-type alteration and mineralization. Four separate predictive evidence layers depicting each the above geological features were extracted from relevant geoscience data and were integrated using a modified fuzzy weights-of-evidence model, which retains the advantages of both fuzzy weights-of-evidence and logistic regression modeling. The results show that most of the known Fe deposits occur in or near, and thus have strong correlation with, areas of high posterior probabilities, as indicated by the delineated prospective areas that occupy only 4.6% of the studied region but contain 88.5% of the total number of known Fe deposits. Different combinations of predictive evidence layers were used to examine prediction uncertainty related to missing evidence. Plots of accumulative number of Fe deposits versus accumulative prospective areas show that the order of the most to the least important evidence of mineral prospectivity in the studied region is: favorable rock types > geochemical anomalies > intrusive rocks > faults. Results of blind testing the prospectivity models indicate that the geological model of Fe mineralization in the belt is suitable for predicting exploration target areas for skarn-type Fe deposits, and suggest that the highest risk in follow-up exploration is related to sequences of carbonates in the Carboniferous–Permian formations that were likely either not mapped or not represented at the present regional scale of mapping.
... This indicates that the prediction with missing evidence for favorable formation is the worst and that favorable formation plays a key control on Fe mineralization, as expected from the geological model. Because the Carboniferous-Permian carbonate formations provide the most favorable host rock (or trap) for skarn-related Fe deposition, some earlier researchers regard the Makeng deposit as a stratabound skarn Fe deposit (e.g., Zhao et al., 1983). In comparison, the curve related to the missing evidence for faults is closest to the xaxis, which shows that the prediction with missing evidence for faults is the best and that fault control on skarn Fe mineralization is less significant compared to the other three geological features. ...
Geochemical data are typical compositional data which should be opened prior to univariate and multivariate data analysis. In this study, a frequency-based method (robust principal component analysis, RPCA) and a frequency-space-based method (spectrum–area fractal model, S–A) are applied to explore the effects of the data closure problem and to study the integrated geochemical anomalies associated with polymetallic Cu mineralization using a stream sediment geochemical dataset collected from the Zhongteng district, Fujian Province (China). The results show that: (1) geochemical data should be opened prior to RPCA to avoid spurious correlation between variables; (2) geochemical pattern is a superimposition of multi-processes and should be decomposed; and (3) the S–A fractal model is a powerful tool for decomposing the mixed geochemical pattern.
Weathering would produce damage to objects. This paper proposed a method to monitor geochemical variations on outcrop surfaces, through in situ measurement using portable X-ray fluorescence (pXRF) analyser at high spatial resolution, and qualitative and quantitative determination of elemental gains and losses based on spatial patterns of elemental concentrations and calculated enrichment factors. Taking into account the representativeness of sample matrices, a weathering diabase profile consisting of saprolite and the corresponding rock was selected. Comparisons were made between the laboratory results and the pXRF results, besides, the difference between the two test modes based on different calibration principles (mining mode: Fundamental Parameters calibration; soil mode: Compton normalization) in measuring multi-matrices was evaluated. The pXRF results were comparable to the laboratory results for most elements (excellent correlation: Ca, K, Mn, Mo, Zn, and V; good correlation: Ti, Rb, and Sr; moderate correlation: Fe, Si, and Zr; bad correlation: Ba and Al). Much lower readings for light elements would be obtained from the mining mode when loose samples were analysed, and the soil mode was more suitable for measuring a weathering profile, and if light elements such as Mg, Al, and Si are involved, the mining mode can be used, and the reading ranges of the light elements will require verification. Elemental enrichment and depletion were discussed based the spatial pattern of elemental concentrations, and four groups of elements of continuous emigration, slight emigration, local immigration caused by later veins, and continuous immigration with weathering were effectively discriminated based on the spatial pattern of elemental enrichment factors in the profile. Using this method we could rapidly ascertain the migration characteristics of multielements and locate the spatial positions of intense weathering, providing a new insight into the measuring and monitoring of chemical changes with weathering in rock outcrop, building stone, and so on.
The Wuyi metallogenic belt can be divided into the South and the North Wuyi metallogenic belt by the ENE-trending Nanping–Ninghua–Ganzhou Tectonic Belt. In the Wuyi metallogenic belt, Paleozoic mineralization, which has caused typical deposits such as the Yongping, Fenglin, and Yushui Cu deposits and the Makeng Fe deposit, exhibits notable variations. However, systematic research on the controlling factors of these mineralization episodes is lacking. In order to understand the Paleozoic minerlization in the Wuyi metallogenic belt, we study the genesis of typical deposits in Wuyi metallogenic belt. The phenomenon of “basal ore control” was observed as different basement units control different ore types in the Wuyi metallogenic belt. We believed that Paleozoic mineralization in the Wuyi metallogenic belt includes siliceous–carbonate Jingshe, Lindi, and Chuanshan Formations, which are related to the Fe–Mn deposits such as the Makeng Fe deposit, Dapai Fe–Pb–Zn deposit, and Luoyang Fe deposit in the Southwest Fujian Province, carbonate formations of the Hutian Group related to Cu deposits such as the Yushui Cu deposit in the North Guangdong Province of the southern Wuyi region, and the Carboniferous Outangdi Formation related to the Yongping and Fenglin Cu deposits in the Northeast Jiangxi Province of the northern Wuyi region. Based on a systematic analysis on typical metallogenic deposits and basement characteristics in the Wuyi metallogenic belt, we proposed that the Paleozoic mineralization is not only controlled by Paleozoic strata and Mesozoic magmatism, but also by the basement. The basement controls Paleozoic Cu mineralizations in the southern and northern Wuyi regions. However, Fe–Mn mineralization is mostly related to Late Paleozoic sedimentation. The superposition and transformation of Mesozoic magmatism to the basement and Paleozoic strata is an indispensable factor in the Cu and Fe–Mn mineralizations in the Wuyi metallogenic belt.
The genesis of the Makeng Fe deposit, located in Fujian Province in southeastern China, has been the focus of numerous studies. Recent studies have revealed that the mineralization and alteration of the deposit may have occurred during the intrusion of granitic magma. In this study, we focus on the magmatic activity that has occurred in the region, as well as the geological context of the Makeng and similar deposits. We have divided the magmatic activity that occurred in the Makeng and adjacent areas into four main stages: the first occurred during the early Yanshanian at ~195 Ma, the second occurred from 150 to 170 Ma (related to Cu–Au–Fe mineralization), the third occurred from 140 to 120 Ma (related to FeMo mineralization and producing the Makeng and Longfengchang plutons), and the fourth occurred from 90 to 110 Ma (related to Ag–Cu–Mo mineralization). We propose that the formation of the Makeng Fe deposit was both spatially and temporally related to local granitic magmatism, and that the granitic magma transported Fe during the formation of the deposit. The Juzhou and Dayang plutons also played important roles in the transport and enrichment of other metals during the formation of the Makeng Fe deposit. The Makeng Fe deposit is a concealed or semi-concealed type of granite mineralization, and its ore genesis was due to multiple coupling, critical transformation, and boundary mineralization processes. The contact areas between the granite and the surrounding rocks, as well as the interfaces between the host rock carbonates and silica-rich sediments, are important targets for future prospecting.
Magmatic activity is of great significance to mineralization not only for heat and fluid it provides, but also for parts of material source it brings. Due to the cover of soil and vegetation and its spatial nonuniformity detected signals from the ground's surface may be weak and of spatial variability, and this brings serious challenges to mineral exploration in these areas. Two models based on spatially weighted technology, i.e., local singularity analysis (LSA) and spatially weighted logistic regression (SWLR) are applied in this study to deal with this challenge. Coverage cannot block the migration of geochemical elements, it is possible that the geochemical features of soil above concealed rocks can be different from surrounding environment, although this kind of differences are weak; coverage may also weaken the surface expression of geophysical fields. LSA is sensitive to weak changes in density or energy, which makes it effective to map the distribution of concealed igneous rock based on geochemical and geophysical properties. Data integration can produce better classification results than any single data analysis, but spatial variability of spatial variables caused by non-stationary coverage can greatly affect the results since sometimes it is hard to establish a global model. In this paper, SWLR is used to integrate all spatial layers extracted from both geochemical and geophysical data, and the iron polymetallic metallogenic belt in south-west of Fujian Province is used as s study case. It is found that LSA technique effectively extracts different sources of geologic anomalies; and the spatial distribution of intermediate and felsic igneous rocks delineated by SWLR shows higher accuracy compared with the result obtained via global logistic regression model.
Makeng type iron deposit is a large deposit in the secondary NE-trending Longzhang basal fracture sag zone of the Late Paleozoic depression of Yongmei. The prospecting breakthrough has been hindered due to the fact that we are not very clear about the type of the strata hosted Makeng type iron deposits. On the basis of field investigation and conscientious study of the results of previous researches, this paper explores ore-controlling factors of the Makeng type iron deposit. It is found that the fold in the Makeng mine district is an overturned anticline instead of one limb of the anticline, and that the Yanshanian thrust nappe structure is the results generated by the subduction of Izanagi plate under the Eurasian plate from southeast to northwest. It is suggested that the Jingshe Formation-Qixia Formation (C2j-P1q) and interface between the Jingshe Formation-Qixia Formation (C2j-P1q) and the Wenbishan Formation (P1w) are the horizon hosted Makeng type iron deposit, and that the thrust nappe structure is also important ore-controlling factors. In addition, this paper also presents the prospecting direction.
The Pantian iron ore deposit is a high-grade iron deposit with great prospecting potential. The orebodies mainly occur in silico-calcium lithologic boundaries in the outer contact zone of the granite, and the mineralization is closely related to the granitic intrusion. But there were little study on the granite. Therefore, petrogeochemistry characteristics and zircon U-Pb age of the granite is studied in this paper to discuss its petrogenesis, tectonic setting, emplacement age and the relationship with the iron ore mineralization. The LA-ICP-MS zircon U-Pb dating of the granite indicates that the granite intruded in Early Cretaceous (131. 68 ±0. 48Ma, MSWD = 1.3). The granite is characterized by high-K calc-alkaline series and weakly peraluminous- metaluminous rocks, and has a moderate smooth REE pattern characterized by lower X REE, higher LREE than HREE, and obvious negative Eu anomalies, and has an intensive enrichment in LILE and different depletion in HFSE. The petrogeochemical analysis shows that Pantian granite belongs to highly fractionated I-type granites and forms on the post-collisional extensional environment. By analyzing the spatial distribution rule and genetic relation between iron orebodies and the granite, we infer that the granite intrusion determine the spatial orientation of main ore bodies, and the granite is the metallogenic geological body of Pantian iron ore deposit which is the typical silicon-calcium mineralization. The lithologic boundaries between the clastic rocks of Lindi Formation and carbonate rocks of Huanglong-Qixia formations are the beneficial ore-forming positions. And the deposit we study in this paper belongs to the typical metallogenic mechanism of "multi-factor coupling, critical transformation, and marginal metallogenesis".
The Makeng Fe-Mo deposit is a large deposit hosted in the interlayer fracture zone between carbonates of Huanglong Formation (C2h) and clastic rocks of Lindi Formation (C1l) at the exo-contact zone of the Juzhou-Dayang granite. The iron ore are closely coexisting with skarns. However, the ore genesis here has still been controversial. In this paper, we studied the mineralogical characteristics of skarns in Makeng Fe-Mo deposit with electron microprobe analysis, which showed that the mineral assemblages of skarns in this deposit mainly consisted of pyroxene, garnet and bustamite. The retrograde altered minerals were comprised of chlorite, epidote, amphibole and quartz. The mineral composition of clinopyroxene are diopside, hedenbergite, and a small amount of johannsenite. Pyroxenoids are mainly composed by bustamite and rhodonite. The end member of garnet is dominated by andradite, with minor grossularite. The amphibole in this deposit can be classified into calcic amphibole. All the mineralogical characters of skarns showed that they were mainly formed under relative oxidizing conditions. The skarns in Makeng Fe-Mo deposit resulted from the metasomatism formed by thermal fluid flowing along the interlayer fracture zones between limestone and clastic rocks, most iron ore hosted in the skarns, usually the magnetites formed later than the skarns and constituted a metasomatic texture, not only replaced skarns widely, but also direct alternated limestone, sandstone in the wall rock; the footwall of main orebody often appeared thick quartzite, furthermore the metasomatic also appeared obvious in clastic rocks. The skarn zonations were widespread in the deposit, consistent with typical skarn-type ore deposits. Combining the geological features with mineralogical characteristics of skarns in the Makeng Fe deposit, it shows that the deposit is a strata-bound skarn-type deposit.
Study of geological processes including: (1) establishment of energy gradients to drive the system, (2) generation of hydrothermal fluids, (3)extraction of metals and chemical ligands for metal complexation from suitable sources, (4) transportation of metals from sources regions to trap zones, (5)deposition of metals triggered by chemical and physical processes that alter the make-up of melts or fluids migrating through trap zones, and (6) preservation of mineral deposits through time is the basis for mineral resource quantitative prediction and assessment (MRQPA) since the forming and preservation of mineral deposits is a spatial-temporal function of geological processes. In this study, geological process-based mineral resource quantitative prediction and assessment for Makeng type iron polymetallic deposits in Fujian Province is implemented. The focuses are to study the critical geological processes and evidences that these processes have occurred, and to evaluate the probability of occurrences of the critical geological processes. This study offers a new prospective for mineral resource exploration, and provides a new strategy for further Makeng type iron polymetallic mineral exploration in Fujian province.
Makeng Fe deposit is a large strata-bound skarn-type magnetite deposit. Juzhou-Dayang granite exposed on either side of Makeng deposit, and had genetic relationship to ore bodies. The SHRIMP ziron U-Pb age of Dayang granite is 132.6 ± 1.3Ma, MSWD = 1.3: The LA-ICP-MS ziron U-Pb age of Juzhou granite is 129.6 ± 0.8Ma, MSWD = 2.3, indicating that they formed in Early Cretaceous, which identified with the time when Makeng deposit (130 ∼ 133Ma, Re-Os age) were formed.Juzhou-Dayang granite is regarded as the weakly peraluminous-metaluminous granite, which is characterized by high silicon, enrichment of alkali, low calcium and magnesium, and high differentiation index. The rocks have high and remarkably varying REE, and their distribution patterns show LREE enrichment with gentle right oblique deviation, and a "V" model characterized by significant negative Eu anomaly: The trace elements compositions are strongly enriched in Rb, U, Th and La and considerably depleted in Ba, Sr, P and Ti: ( 7Sr/ Sr) j = 0.70878-0.71349, εnd(t) = -7.2- -8.6,fSm/nd = -0.27 -0.16, t2DM =1511 ∼1637Ma, ( 206 Pb/ 204 Pb), =18.588 -18.955, ( 207Pb/ 204Pb), = 15.660-15.682, ( 208Pb/ 204Pb), = 38.935-39.168 , μ = 9.54 -9.59, w = 36.77-38.13. The petrogeochemistry and isotopic characteristics of Dayang-Juzhou granite show that it is regarded as the crust-derived type granite, and experiences high differentiated evolution. The lithospheric thinning in relation to paleo-Pacific plate is a likely responsible mechanism for their formation. The magma sources of the Dayang-Juzhou granite mainly derived from Proterozoic crustal materials, but also involved some portions of EMU component, which reduced crustal residence age of the granite.
Makeng Fe-Mo deposit is a large strata-bound skarn-type deposit occurred in the exocontact zone of the Juzhou-Dayang granite and hosted by interbedfaults between Huanglong Formation (C 2h) carbonates and Lindi Formation (C 1l) clastic rocks. Seven molybdenite samples separated from the Makeng skarn ore bodies were used for Re-Os dating. The obtained the model ages range from (131.9±1.9) Ma to (133.3±2.3) Ma, averaging at (133.0±0.8) Ma, indicating that the major metallogenic stage occurred at the Early Cretaceous, which is consistent with the emplacing age of the host rock Juzhou granitic pluton. Our results suggest that they are products of the same epoch magma, structure, and fluid activities. Five out of seven molybdenite samples show Re contents at 0.47×10 -6~5.14 ×10 -6, and the other two at 51.87×10 -6 and 186.2×10 -6, respectively. Combined with fact that the Juzhou-Dayang pluton are the crust-derived granite, we infer that the ore-forming material mainly derived from upper crust with minor addition from the mantle. The metallogenic epoch of Makeng Fe-Mo deposit may consider as the response to the Late Mesozoic regional lithospheric thinning in the South China block.
In this paper, it is shown that the element concentration in the stream sediments in the covered areas can be very low due to decay and mask effects even if a thin layer of overburden exists. The examples introduced in the paper for prediction of mineral deposits of skarn types have demonstrated that the nonlinear singularity and generalized self-similarity theories and methods can be used to map anomalies for locating undiscovered mineral deposits in areas covered by transported regolith. Three main aspects of difficulties facing mineral exploration and mineral deposit prediction in covered areas are discussed in the paper which include weak anomalies detection and recognition, decomposition of complex and mixing anomalies due to multiple geo-processes, and application of evidential layers with missing or incomplete information due to covers. Various models have been proposed for prediction of various objects including felsic intrusions, skarn and hydrothermal alterations and local geochemical anomalies. Several datasets, including 1:200 000 scale geological maps, stream sediment geochemical data, aeromagnetic and gravity data were applied for delineation of potential target areas for Fe mineral deposits of volcanic skarn and hydrothermal types in the areas covered by desert and Ternary to Quaternary sediments.
This contribution briefly reviews, in its first part, the history of the Chinese literature on ore deposits since its emergence after the turn of this century, till 1988. Influence of the changing political and economic conditions on the character of the literature is emphasized.In the second part, the existing literature categories are reviewed and the various techniques of data harvesting discussed.
Mill concentrates of ore sulfides from three magmatic-hydrotherml ore deposits were stud- ied for δ34S at the granite-hosted Xihuashan deposits, and carbonate-hosted Shizhuan and Huashaping deposits. These ore deposits occur in the South China Fold System, which is composed of mid-Paleo- zoic "miogeosynclinal" sediments dominant in carbonates toward the Devonian age. Averages of the ore sulfides are -0.9 permil for the Xihuashan, +7.0 permil for the Shizhuan and +13.2 permil for the Huashaping deposits. Endogranitic ore sulfur of the Xihuashan and the Shizhuan deposits are consid- ered magmatic, derived from by ca.+2 ‰ δ34S granitic magma, but the carbonate-hosted ore sulfurs at the major part of the Shizhuan and Huashaping deposits are much higher than those expected from rock sulfur δ34S values of the Yanshanian granites of the South China Fold System. Thus, addition of 34 S-enriched sulfur into the ore solutions is considered. Devonian and Carboniferous carbonates of the South China Fold System are very high in the δ34S values of structurally substituted sulfate (SSS) sulfur, averaged as +25.7 and +15.7 permil, respec- tively, which are higher than the reported values from other areas of these ages. The SSS contents of the Paleozoic carbonates are very low at present, but recent carbonates contain typically 0.1 to 1 % equivalent sulfate. The very low SSS contents in the wall rock carbonates and high δ34S values in the ore sulfides may have been resulted from carbonate SSS extracted during recrystallization and some- how mixed with magmatic ore fluids when the granitic magmas intruded, then precipitated as the ore sulfides.
Abstract Manganoan skarns consist of special Mn (Ca, Mg, Fe, Al) silicate metasomatic minerals and are usually associated with Pb-Zn(Ag) mineralization. They occur chiefly along the lithologic contacts or faults and fractures of carbonate wall rocks distal from the intrusive contact zone, and are combined with Fe, Cu, W, Sn and Cu-bearing calcic or magnesian skarns occurring in the contact zones to constitute certain metasomatic zoning. Manganoan skarns are formed later than calcic or magnesian skarns. Their rock-forming temperatures are lower than those of calcic or magnesian skarns. The mineral assemblages of manganoan skarns occurring in different carbonate rocks (limestone or dolomite) are notably different.
The Bajiazi Zn–Pb–Ag skarn deposit is located in northwest Liaoning Province, China. The orebodies occur in a contact zone between Yanshanian (170–177.4 Ma) quartz monzodiorite and Middle Proterozoic dolomitic marble of the Gaoyuzhuang Formation as well as along the NW- and NS-trending fault systems in carbonate wall rocks.Metasomatic mineralization zoning in the deposit is very pronounced. From the intrusive contact zone to dolomitic marble along the NW-trending fault system, three ore-bearing skarn zones may be distinguished: magnesian skarn zone (Fe–Mo)→manganoan–magnesian skarn zone (Cu–S–Fe–Pb–Zn–Ag)→manganoan skarn zone (Zn–Pb–Ag). Magnesian skarn is composed of diopside, forsterite, tremolite, spinel, phlogopite, chondrodite, and serpentine, accompanied by magnetite, pyrite, and molybdenite. Manganoan–magnesian skarn consists mainly of manganoan diopside, manganoan tremolite, mangano-anthophyllite, and manganocummingtonite with minor spessartine and pyroxmangite, The associated ore minerals are pyrite, pyrrhotite, and chalcopyrite, with subordinate magnetite, sphalerite, galena, and Ag-bearing minerals. Manganoan skarn is composed chiefly of spessartine, pyroxmangite, magnesian rhodonite, manganocummingtonite, and manganopyrosmalite, with the associated ore minerals sphalerite, galena, alabandite, and Ag-bearing minerals.Studies of fluid inclusions and S, Pb, O, and H isotopic compositions suggest that ore-bearing fluids flowed from the deep contact zone of the intrusion in the southeast to the shallow depth in the northwest with decreasing temperatures, oxidation state, and increasing pH. When the ore-bearing fluids migrated, their frontal part constantly reacted with the dolomitic carbonate wall rocks to form different types of skarn and mineralization. Sulfur and lead (zinc) were mainly derived from the deep lower crust, while the Middle Proterozoic wall rocks may have provided most Al, Si, Mg, Ca, and Mn for the formation of skarns.The zonal model reflecting the variations in metallization assemblage, skarn mineralogy, composition, δ34S isotope values, and fluid inclusion characteristics can be used as a guide to exploration for Zn–Pb–Ag skarn deposits.
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