The newly identified greisen-hosted Nb-Ta mineralization in the Qidashan iron deposit, Liaoning Province, China, offers a unique opportunity to explore how hydrothermal processes contribute to the enrichment of critical metals. In this study, an integrated analytical approach of petrographic observation and scanning electron microscopy-energy-dispersive spectrometer (SEM-EDS), electron probe microanalyzer (EPMA), and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) U-Pb dating of columbite-group minerals (CGMs) were employed to systematically decipher the paragenetic sequence, micro-structure, elemental composition and mineralization age of CGMs, aiming at the genesis of greisen-hosted Nb-Ta mineralization. The mineralization is characterized by the abundant occurrence of CGMs. Three generations of CGMs and two mineralization stages are distinguished: stage I contains CGM Is and CGM IIs, with Nb2O5 ranging from 25.7 to 69.56 wt.% and Ta2O5 from 5.8 to 52.5 wt.%; stage II contains CGM IIIs, with Nb2O5 between 59.5 and 71.5 wt.% and Ta2O5 between 3.5 and 16.2 wt.%. CGM Is consist of euhedral, homogeneous crystals of more than 100 mu m, exhibit low Ta/(Nb + Ta) ratios (0.05-0.06) and high Mn/(Fe + Mn) ratios (0.19-0.26), and belong to columbite-Fe. CGM IIs generally overgrow on CGM Is with hydrothermal overprinting textures, and show significant compositional gaps compared to CGM Is, exhibiting higher Ta/(Nb + Ta) ratios (0.13-0.55) and restricted Mn/(Fe + Mn) ratios (0.15-0.18), with some belonging to columbite-Fe and others to tantalite-Fe, which reveals a transition from magma to "hydrosilicate fluid". CGM IIIs are mainly anhedral and homogeneous, with a grain size of less than 50 mu m. However, some CGM IIIs overgrow on CGM IIs and/or CGM Is with patchy textures indicative of subsequent hydrothermal overprinting of hydrosilicate fluid, forming a coarse-grain size over 100 mu m. CGM IIIs are characterized by lower Ta/(Nb + Ta) ratios (0.03-0.14) and variable Mn/(Fe + Mn) ratios (0.08-0.26), and they belong to columbite-Fe. LA-ICP-MS U-Pb dating yields weighted mean Pb-206/U-238 ages of 2646 +/- 15 Ma for stage I and 2500 +/- 28 Ma for stage II, indicating two-stage Nb-Ta mineralization. The early mineralization may correlate with the partial melting of volcanic-sedimentary rocks due to the geothermal anomalies associated with similar to 2.7 Ga submarine volcanism, and the late mineralization formed by the magmatic hydrothermal activities related to emplacement of the Qidashan granite in 2.5 Ga. We therefore propose that the two-stage greisen-hosted Nb-Ta mineralization probably widely occurred in these sedimentary-metamorphic iron deposits in the Anshan-Benxi area and even in the northern edge of the North China Craton, and it may provide new insights for evaluating the Nb-Ta resource potential in similar Algoma-type iron deposits globally.

To elucidate the spectral diagnostic features and geological significance of fuchsite from the Gongchangling Iron Mine, Liaoning Province, and fill the gap in the spectral research of fuchsite in the BIF-related hydrothermal system and supplement the deficiencies in the research on the spectral identification and component response characteristics of fuchsite, this research conducted systematic mineralogical and spectroscopic analyses on fuchsite samples collected from the No. 2 mining area of the Gongchangling deposit, The methodologies employed included Electron Probe Microanalysis (EPMA), Near-Infrared Reflectance Spectroscopy (NIR), and Raman Spectroscopy. NIR spectra revealed absorption features centered around similar to 450 and similar to 620 nm, which are characteristic signatures of Cr3+ electronic transitions within the octahedral sites. Raman spectroscopy identified characteristic peak clusters at approximately 305, similar to 350, similar to 524, similar to 551, and similar to 610 cm, attributed to CrO vibrational modes, along with a distinct Cr O stretching vibration peak near similar to 842 cm. Variations observed in spectral characteristics, such as the positions of the NIR similar to 2 200 nm feature and the Raman similar to 551 cm peak, are correlated not only with the degree of Cr3+ substitution for Al3+ but also potentially indicate formation conditions associated with high-temperature and acidic hydrothermal environments. The research results established the NIR and Raman spectral identification type characteristics of fuchsite in Gongchangling Iron Mine, By studying the clear correlation between spectral peak features and component content, it provides the possibility of using spectral semi-quantitative assessment of Cr content and indicating the relative physicochemical conditions for its formation. It has demonstrated the application potential of NIR and Raman spectroscopy techniques in the rapid identification of fuchsite, semi-quantitative estimation of Cr content and tracing of BIF-related hydrothermal processes, providing spectroscopic basis and methods for exploring possible emerging structure hydrothermal events in the Anben region.

The Anshan-Benxi greenstone belt (ABGB) in the northeastern North China Craton (NCC) preserves similar to 3.88-2.5 Ga basement rocks, among which the Anshan area has been highly studied due to large number of valuable Neoarchean banded iron formations (BIFs) and thick-bedded metasedimentary rocks. However, few researches focus on the metasedimentary rocks of the Waitoushan-Gongchangling-Benxi (WGB) region in the ABGB. Besides, their provenances still remain puzzled. In this study, we present new whole-rock major and trace element data for metasedimentary rocks in the Waitoushan area and collect 59 previously published geochemical datasets for metasedimentary rocks from across the ABGB, with the aim of determining their provenances, particularly their felsic portions. Collectively, the ABGB metasedimentary rocks consist of chlorite amphibole schists, biotite felsic gneisses/schists, phyllites, biotite amphibole gneisses, garnet biotite gneisses, and two-mica quartz schists. Sixty-eight metasedimentary rocks are geochemically classified into greywacke, shale, and Fe-shale. Greywacke, shale and some Fe-shale samples yield fractioned rare earth element (REE) patterns and high REE abundances that are comparable to those of the average Archean upper continental crust (AUCC), whereas the remaining Fe-shale samples exhibit flat REE patterns and low REE abundances due to the low or absence of Th, U, and LREE-enriched minerals, such as monazite and allanite. According to the chemical index of alteration (CIA), chemical index of weathering (CIW) values and A-CN-K diagram, all metasedimentary rocks exhibit weak to moderate degrees of weathering. Narrow SiO2/Al2O3 ratios and index of compositional variability (ICV) values greater than 1 indicate low recycling and immaturity. The Al2O3/TiO2 ratios, REE patterns and abundances imply that the shale and graywacke were derived from predominantly felsic-related rocks, whereas the Fe-shale sources were hybrid provenances of mafic and felsic-related rocks. We summarize 1612 zircon Lu-Hf isotopes and 129 whole-rock Nd isotopes of sedimentary rocks, volcanic rocks and granitic plutons from the ABGB and surrounding areas to determine where the felsic and mafic provenances of the sedimentary rocks in the ABGB originated. The volcanic rocks in the ABGB provide the dominant mafic sources, whereas felsic provenances may have been supplied from the southern Liaoning granitic plutons and felsic volcanic rocks. In this study, a metavolcanic rock interbedded with sedimentary rocks yielded a metamorphic age of similar to 2512 Ma, limiting the minimum depositional age. Combined with the detrital zircon spectrum from the ABGB sedimentary rocks, the depositional ages of these sedimentary rocks range from similar to 2.53-2.51 Ga. On the basis of arc- and back-arc-related volcanic rocks and the distribution of sedimentary rocks, we propose that these metasedimentary rocks formed under a late Neoarchean arc to back-arc basin tectonic domain.

Gongchangling iron deposit is famous for its large amount of high-grade magnetite ore, thus most of the researches focused on Gongchangling mining area Ⅱ due to the bulky high-grade iron ore. In this study, the U-Pb dating of the columbite-group minerals from the hanging wall granite in Gongchangling mining area Ⅰ yields two ages, i.e., 2501 ± 14 Ma and 1845 ± 20 Ma. The chemical compositions of the columbite-group minerals of both ages are always characterized by Nb > Ta, Fe > Mn, low U/Th, and relatively enriched HREEN content, in consideration of the regionally ∼1.85 Ga mono- and multi-mineral uranium mineralization, the rare metal mineralization should be of NYF-type. The ∼2.50 Ga mineralization is coeval with the Lijiapuzi pegmatite Nb-Ta deposit, indicative of the excellent regional late Neoarchean Nb-Ta mineralization potential in eastern Liaoning Province; the ∼1.85 Ga event of Nb-Ta mineralization suggests that the widespread Paleoproterozoic plutons within Jiao-Liao-Ji belt and Trans-North China Orogen should be concerned in the near future. The intimate spatiotemporal relationship implies that the Paleoproterozoic Nb-Ta mineralization and the high-grade iron ores in the Gongchangling deposits were probably the products of the same geologic process, providing critical insights into the ore-forming process of both deposit types.

Banded iron formations (BIFs) in the Anshan-Benxi region in the North China Craton have made a significant contribution to economic benefits. The Xiaolingzi BIF, south of Anshan, was interpreted as Dayugou Formation, while the Qijiagou BIF, east of Qidashan, was believed to be asynchronous Yingtaoyuan Formation. However, the latest geochronological data for these two BIFs indicate that they deposited simultaneously instead. In this study, we report new geochemical and geochronological data from the Xiaolingzi and Qijiagou BIFs, aiming to decipher their deposition age, origin signatures and depositional setting. Both Xiaolingzi and Qijiagou BIF samples were dominated by alternating iron-rich and quartz-rich microbands, accompanied by lower amounts of hematite, pyrite and silicate phases of cummingtonite and biotite/muscovite. SiO2 and Fe2O3T dominated the major elements in all BIF samples. Most BIF samples yielded nil to low contents of TiO2, Al2O3, Zr, Th, rare earth elements (REE) and +Y; conspicuous positive Eu and Y anomalies; depletions of LREEs; and enrichments of HREEs. This composition represents pure chemical sediments formed by a mixture of high-T hydrothermal fluids and seawater, except one BIF sample with terrigenous detrital involvements. According to zircon U-Pb dating analyses, metamorphosed sedimentary rocks and biotite quartz schists were interbedded in the Xiaolingzi BIF and Qijiagou BIF samples and yielded a maximum depositional age of -2552 Ma. We compile nearly all detrital zircon ages for metasedimentary rocks from the entire Anshan-Benxi region and propose that the maximum depositional age is -2.53 Ga. In light of the accompanying metamorphosed volcanic-sedimentary rocks and VMS Cu-Zn mineralization in northern Liaoning, the Xiaolingzi and Qijiagou BIFs deposited under a typical back-arc basin setting.

The Qidashan iron deposit, which is the second-largest BIF-hosted high-grade iron deposit in the Anshan-Benxi areas, hosts chlorite-rich altered rocks and greisenized rocks that exhibit prominent Nb-Ta mineralization in proximity to high-grade iron ore bodies. This provides new clues to the ore-forming mechanism of BIF-hosted high-grade iron ore. In this study, we present new U-Pb dating results for columbite-group minerals (CGMs) from the altered rocks and granites in the Qidashan iron deposit, along with bulk major and trace element geochemical data from high-grade iron ores, BIFs, granites, chlorite-rich altered rocks, and greisenized rocks. The results indicate that the U-Pb dating of the CGMs yields similar ages among the Qidashan granite, chlorite-rich altered rocks, and greisenized rocks, suggesting a genetic linkage between the granite and the alteration processes. The geochemical features indicate that the altered rocks proximal to the high-grade iron ore bodies exhibit slight REE fractionation, moderate to strong negative Eu anomalies, higher contents of W, Sn, Cs and Rb, and lower contents of Ni than distal altered rocks do, indicating that the high-grade iron ores probably represent the ore-forming fluid pathways. In summary, a hydrosilicate fluid superimposition model was proposed, i.e., soon after the emplacement of the Qidashan granite, hydrosilicate fluids derived from the highly fractionated distal part of the granite migrated along various fractures and metasomatized the incipient granitic veins, BIFs, and their wall rocks, leading to the formation of greisenized rocks, high-grade iron ores, and chlorite-rich altered rock, respectively. These processes also facilitated the introduction of rare metal elements, such as Nb, Ta, Th, U, and LREEs, into both the altered rocks and high-grade iron ores. These findings highlight the potential for Nb-Ta mineralization in eastern Liaoning Province and provide new insights into the metallogenic evolution of highgrade iron ore in Qidashan deposit.

Gongchangling iron mine is the largest BIF-hosted high-grademagnetite ore deposit in China,various scholars have carried out many researches,however few studies are related to Raman spectra of magnetite.This paper measured the Raman spectra of magnetite in typical BIF ore and high-grade iron ore of Gongchangling by HORIBA XploRAPLUS micro-Raman spectrometer.The results show that the peaks of magnetite in BIF at 300,550 and 670 cm-1 shift to high wavenumber,which should be related to the increase of the average oxidation state of magnetite in BIF and the decrease of miner allattice size caused by the isomorphic substitution of trace elements.The Raman peak intensities of magnetite in high-grade iron ore increase obviously,probably due to the decrease of the overall content of trace elements and,correspondingly,the relative increase of iron ion content in magnetite.Some magnetites in BIF ore show weak Raman spectral features of hematite,which may be related to the epigenetic oxidation after the formation of magnetite.X-ray diffraction(XRD)analysis shows that the main iron mineral in the high-grade ore is magnetite,whereas the magnetite in the BIF ore is more similar to magnesioferrite.The results of SEM-EDS suggest that the contents of trace elements in the magnetite from high-grade iron ore are lower than those from BIF ore,i.e.,experiencing the process of"purification",which is consistent with the abovementioned conclusion.The research indicates that Raman spectra measurement is proven to be a fast,simple,reproducible and non-destructive method and can be used to estimate the overall content of trace elements of magnetite and further distinguish the magnetite both in BIF and high-grade iron ores of Anshan-Benxi area.

There are two kinds of chlorites occurred in Anshan area, among which the hydrothermal Fe-chlorite with longer Fe-OH wavelength is spatially related to the high-grade magnetite ore, meaning that wavelength mapping of chlorites can be used to target the BIF-hosted high grade iron ore. In this article, quadratic polynomial, cubic spline, and quartic polynomial method were used to interpolate the absorption wavelength near 2250 nm of China ZY1-02D satellite hyperspectral image. The result of quadratic polynomial is continuous without data overlapping or intervals, thus most suitable for discrimination of the chlorites. The field truth shows that the spatial distribution of Fe-chlorite, validated by XRD analysis, is not only in accordance with that of high grade magnetite ore bodies, but also consistent with the recently discovered concealed iron bonanza. The study shows that hyperspectral remote sensing techniques can play significant role in the exploration of magnetite iron ore in east Liaoning Province.

铌(Nb)、钽(Ta)广泛应用于全球高新科技领域,是不可替代的稀有金属资源,在中国,铌钽属于紧缺战略性矿产. 铌钽成矿主要与内生作用有关,国内外目前发现的铌钽矿床几乎都产于过铝质花岗岩、花岗伟晶岩、碱性花岗岩、碳酸岩等侵入体中.

1 研究目的(Objective) 铌和钽物理化学性质相似,在自然界中常相伴产出,在内生和外生条件下都可富集成矿.内生铌钽矿床主要与岩浆作用有关,根据赋矿岩石的特征被分为花岗岩型、花岗伟晶岩型、碳酸岩型和碱性岩型.最近,笔者在华北克拉通北缘的辽宁齐大山沉积变质型铁矿中新识别出一种铌钽矿石类型,为富铁矿体边部的富绿泥石蚀变岩型铌钽矿化,与热液作用密切相关,为认识铌钽成矿过程和拓展找矿空间提供了新线索和支撑.

As rock fractures caused by micro-seismic events has potential safety hazards to underground workers, it is often necessary to accurately locate the micro-seismic source for hidden danger investigation. Micro-seismic data are generated in complex underground environments which are significantly affected by random noise. These data greatly influence subsequent micro-seismic source location, energy estimation, and disaster monitoring. In this paper, a new denoising method based on Time-Frequency Peak Filtering (TFPF) and Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) is proposed for micro-seismic data. Micro-seismic data are decomposed into several Intrinsic Mode Functions (IMFs) by CEEMDAN. Then, discriminant factors are used to determine which IMF needs to be denoised by TFPF. Finally, the denoised result is reconstructed by inverse CEEMDAN. By comparing and analyzing different entropies, Fuzzy Entropy (FE) is selected as the best discriminant factor. The CEEMDAN-FE-TFPF denoising method can effectively avoid the influence of fixed window length of the conventional TFPF method. The effectiveness and superiority of this method are verified by experiments of synthetic and actual data.

遥感技术可以快速地识别与矿化有关的热液蚀变,并通过高效精准的分析解译为找矿勘查提供帮助.以典型的鞍山式铁矿——弓长岭铁矿为研究对象,采用成像质量较好的Landsat 8 OLI遥感数据源,在遥感图像预处理的基础上,利用羟基矿物和铁染矿物在特定波段的吸收或反射特征,以主成分分析法为主、波段比值法为辅,对研究区遥感蚀变信息进行提取,并对提取的专题信息进行了分析和验证.结果表明:弓长岭地区蚀变异常较分散,铁异常主要分布在矿区中心且向南延展,蚀变信息最强区域为露天采区;羟基异常范围较大,且矿区南部有较多弱异常分布.同时,经蚀变信息提取结果对比分析,在研究区内采用主成分分析法可以有效地抑制干扰信息,提取铁和羟基蚀变信息效果较好.提取结果与研究区内已知矿点吻合较好,证明蚀变信息对矿床有较好的指示意义.

The Gongchangling deposit is a representative banded iron formation (BIF) in China, in which developed several high-grade magnetite ores. The surrounding alteration rocks recorded the genesis information of the high-grade ores. However, the study related to alteration processes remains poor. In this study, we investigate the sub-types and formation temperature of chlorite using hyperspectral imaging and electronic probe microanalysis (EPMA), and deciphered the elemental migration trend during alteration processes by whole-rock geochemistry. The chlorites in the alteration rocks were divided into three sub-types according to the spectral features of the Fe-OH band near 2250 nm. The range of wavelength position is approximately 2250–2255 nm for chlorite-I, 2255–2260 nm for chlorite-II, and 2260–2265 nm for chlorite-III. The variation in Mg# is 0.32–0.44 in chlorite-I, 0.20–0.34 in chlorite-II, and 0.15–0.23 in chlorite-III, which is consistent with the range of wavelength position. The hydrothermal alteration resulted in the enrichment of iron and the depletion of silicon. The results shed new light on the recognition of chlorite sub-types and deciphered the hydrothermal alteration processes of high-grade magnetite ores, which proposed an effective method for mineralogical mapping.

辽宁海城-大石桥地区是中国最大的菱镁矿基地,露天开采使周边生态环境恶化.为了更好地开发矿山、保护地区生态,本文对其环境质量进行监测与评价.选取1984年、1990年、2007年、2010年和2016年的Landsat遥感影像,提取绿度、湿度、干度和热度四个生态因子,通过主成分分析法构建遥感生态指数(RSEI)模型,并结合土地利用类型的变化来分析研究区生态环境演化.结果表明,1984—2016年间RSEI均值呈先上升后下降再上升的趋势.通过RSEI值的分级结果可以看出,生态质量差的区域整体呈现先升高后下降的趋势,生态环境质量优的区域呈波动上升趋势,生态质量良的区域面积最大.结合RSEI值的分级和土地利用分类,分析研究区生态环境变差的主要原因:一是城镇化规模扩大,林地及耕地被侵占或林地被改造为耕地;二是菱镁矿的露天开采及排土场影响了矿区环境.后期生态环境改善则是因为矿区复垦、植树造林,提高了林地面积,改善了环境质量,环境治理成效明显.该研究可为露天采矿地区的生态监测及治理提供一定的科学依据.

Most of the rare metal pegmatite deposits in China lie in West, Central and South China, and the Lijiapuzi Nb-Ta deposit is the only pegmatite-type Nb-Ta deposit in Northeast China, therefore a detailed study of the Lijiapuzi deposit is of great importance to the metallogeny and exploration of rare metal deposits in Northeast China. The Nb-Ta bearing pegmatites in Lijiapuzi district are composed of a microcline wall zone, a muscovite (lepidolite)-albite intermediate zone and a quartz core, and the rare metal mineralization mainly occurs in the intermediate zone and is intimately related to the albitization. The lithogeochemical features indicate that Lijiapuzi pegmatoids are rich in silicon and alkaline, poor in calcium, magnesium, titanium and phosphorus, and belong to peraluminous granitoid rocks. The enrichment of large ion lithophile elements (LILEs) and depletion of high field-strength elements (HFSEs), the distinct right-inclined REE pattern with obvious Eu negative anomaly, lower ratio of Nb/Ta and higher ratio of La/Nb and Rb/Sr indicate that the pegmatite was of a crustal origin and formed in relatively extensional tectonic setting of post-orogenesis. The pegmatites in Lijiapuzi area can be divided into two categories, i.e., the NW-trending pegmatites are shorter and thicker, with obvious zoning and localized in the upper part of the near-surface, while the NE-trending pegmatites are longer, thinner, devoid of zoning and localized in the lower part of the district. This probably means that excellent ore prospecting potential exists in the lower part of the Lijiapuzi district.

Regolith-hosted rare earth element (REE) deposits predominate global resources of heavy REEs. Regoliths are underlain by various types of igneous rocks and do not always host economically valuable deposits. Thus a feasible and convenient method is desired to identify REE mineralization in a particular regolith. This study presents a detailed visible short-wave infrared reflectance (VSWIR) spectroscopic study of the Renju regolith-hosted REE deposit, South China, to provide diagnostic parameters for targeting REE orebodies in regoliths. The results show that the spectral parameters, M794_2nd and M800_2nd, derived from the VSWIR absorption of Nd3+ at approximately 800 nm, can be effectively used to estimate the total REE concentrations in regolith profiles. M1396_2nd/M1910_2nd ratios can serve as proxies to evaluate weathering intensities in a regolith. Abrupt changes of specific spectral features related to mineral abundances, chemical compositions, and weathering intensities can be correlated with variations of protolith that formed a regolith. These VSWIR proxies are robust and can be used for exploration of regolith-hosted REE deposits.

Regolith-hosted ion-exchangeable rare earth element (REE) mineralization in South China dominate the global source of heavy REEs. The lack of studies on spectral features of ion-exchangeable REEs limits the application of visible/near infrared reflectance (VNIR, 350-2500 nm) spectroscopy for rapid identification of regolith-hosted REE deposits in prospective areas. This paper presents a systematic study on VNIR spectral features of ionexchangeable REEs hosted by a series of synthetic REE-adsorbed clay minerals and natural regolith samples. The results show that ion-exchangeable Nd3+, Dy3+, Ho3+, Er3+ and Tm3+ display diagnostic absorption features at the bands of 730-870, 805, 641, 652, and 684 nm. Specifically, the Nd3+ related absorption bands of regolith samples at -800 nm show a shoulder at -802 nm that are distinguishable from unweathered primary REE (-bearing) minerals. The maxima of second derivative curves derived from the Nd3+ absorption at -802 nm, M802_2nd, can be used to quantify variations of ion-exchangeable REEs in regoliths. Nevertheless, the absorption features of REE3+ ions could be subdued due to an overlapping problem caused by the broad absorption bands of Fe-oxides in the range of 700-900 nm. The obtained VNIR spectra of ion-exchangeable REEs provide critical supplement to spectral library for REE-bearing minerals. This study demonstrates that field-based VNIR spectroscopy can be deployed as a powerful tool for regional and deposit-scale exploration of regolith-hosted ionexchangeable REE resources.

Most hydrothermal ore deposits have experienced multiple stages of hydrothermal activities and the overprinting makes the footprints of ore fluid pathway difficult to identify, which prevents us from targeting the mineral resource effectively. In this paper, the altered wall-rocks from all accessible underground tunnels of No.101 lode in the Shihu Gold Deposit, North China were investigated by the combined methods of petrographic microscopy and short wave infrared spectroscopy (SWIR). The results show that there are three types of alteration in the Shihu Gold Deposit, i.e., the proximal illitic alteration, the transitional chloritic alteration and the distal propylitic alteration. The wavelength (wvl) of the 2200 nm absorption features (2200wvl) of the illitic alteration rocks around ore bodies are shorter than those from the barren areas, suggestive of the compositional variation of illites derived from the multiple stages of hydrothermal fluids. The domains with higher absorption depth at 1400 nm, 1900 nm and 2200 nm (1400D, 1900D and 2200D) are spatially coincident with the economic ore bodies, which is well in accordance with the field truth that the gold mineralization in the Shihu mining district is intimately related to illitic alteration. The band ratio of 2200D/1900D, which is regarded as the proxy to illite crystallinity, is positively related to the temperature of fluid inclusions. The coincidence between low crystallinity and gold mineralization reflects the fact that fluid temperature during the main mineralization stage was relatively low compared to those of previous stages. Detailed investigation indicated that the economic ore bodies mainly occurred in the structural dilation domains, i.e., the widened portions of the ore-controlling structure were more suitable for the fluids migration and probably acted as the fluid up-flow zones. Therefore, SWIR spectroscopy of illite is a powerful tool to trace the ore fluid pathway, which is crucial to the understanding and exploration of gold mineralization. Based on the geological significance of the SWIR signatures and the investigation of the ore-forming conditions, it can be concluded that there are two fluid up-flow zones in No.101 lode, one of which lies on the north of No.13 cross section and centered at No.7 cross section, whereas the other on the south of No.17 cross section and centered at No.27 cross section. As a result, two steeply dipped ore bodies were formed along the up-flow zones. According to this ore-forming analysis, the location centered at No.47 cross section with elevation below 150 m would be an ideal site for the formation of a third ore body. This has recently been verified by underground drillings in the Shihu Gold Deposit (Yougang Zhang, pers. commun. 2020).

Visible/Near Infrared Reflectance spectroscopy (350-2500 nm) is an efficient and effective tool to identify and semi-quantify clay minerals, Fe3+ (oxyhydr)oxides, and their crystal-chemistry/structure. Even so, there have been few studies systematically describing how spectroscopy can be applied to mineralogical evolution during weathering. This study investigated reflectance spectra of a long core of a thick basaltic weathering sequence in Hainan Island and a series of transformation products from montmorillonite to kaolinite to present spectral features associated with weathering trends. In combination with X-ray diffraction and geochemical results, mineralogical transitions and weathering intensity of the core samples were described from a spectroscopic perspective. Several different pmtoliths were spectroscopically recognized in the Hainan weathering sequence, consistent with geological observation and geochemical analysis. Overprinted on these multiple protoliths was a discernable weathering sequence observable by infrared spectroscopic methods. Clay minerals changed upwards in section from TOT type (nontronite) to TO type (kaolinite), and finally to O type (gibbsite) hydroxide clay-size particles as the result of gradual hydrolysis of silicates and leaching of mobile elements with weathering. The relative abundance of hydroxyl to interlayer water, observable by the band depth ratio of spectral absorptions around 1400 nm and 1900 nm (BD1400/BD1900), increased progressively and correlated positively with the chemical index of alteration and Al2O3 concentration. The increasing BD1400/BD1900 index value with weathering was the result of gradual leaching of interlayer cations (e. g. Na+, K+), and their water complexes within interlayers, and gradual formation of M-OH layers by hydrolysis. Owing to leaching of Mg and release of Fe, the octahedral M-OH formed by hydrolysis was gradually dominated by Al-OH. Reflectance spectroscopy is a powerful tool to identify protolith changes in weathering sequences and for studying clay mineralogical transitions and weathering intensity. This spectroscopic approach could have great value for understanding weathering related to paleoclimate on Earth or other planets using field spectroscopy and remote sensing.

作为人类扰动活动的重要方式之一,矿业开发对区域生态质量具有巨大的影响.本文以辽宁省辽阳市弓长岭地区为例,基于1999、2003、2010、2015和2020年的Landsat遥感影像,采用遥感生态指数(RSEI)对弓长岭地区生态环境质量进行评价.结果 表明:1999-2020年总体的生态质量以优为主,所占面积比例均达到80％以上;5个时期的RSEI均值分别为0.927、0.931、0.891、0.883、0.894,其整体呈先略微上升,接着持续下降,最后上升的变化趋势;生态质量变化明显的主要区域为矿区以及城镇.弓长岭地区生态质量的变化与该地的矿业开发活动密切相关.