Search Results (44)

The southeastern Yunnan region in the southwestern Nanpanjiang Basin is one of the most important manganese enrichment zones in China. Manganese mineralization is mainly confined to marine mud–sand–carbonate interbeds of the Middle Triassic Ladinian Falang Formation (T₂f), which contains several medium to large deposits such as Dounan, Baixian, and Yanzijiao. However, the geological processes that control manganese mineralization in this region remain insufficiently understood. Understanding the tectonic evolution of the basin is therefore essential to unravel the mechanisms of Middle Triassic metallogenesis. This study investigates how rift-related tectonic activity influences manganese ore formation. This study integrates global gravity and magnetic field models (WGM2012, EMAG2v3), audio-frequency magnetotelluric (AMT) profiles, and regional geological data to investigate ore-controlling structures. A distinct gravity low–magnetic high belt is delineated along the basin axis, indicating lithospheric thinning and enhanced mantle-derived heat flow. Structural interpretation reveals a rift system with a checkerboard pattern formed by intersecting NE-trending major faults and NW-trending secondary faults. Four hydrothermal plume centers are identified at these fault intersections. AMT profiles show that manganese ore bodies correspond to stable low-resistivity zones, suggesting fluid-rich, hydrothermally altered horizons. These findings demonstrate a strong spatial coupling between hydrothermal activity and mineralization. This study provides the first identification of the internal rift architecture within the Nanpanjiang Basin. The basin-scale rift–graben system exerts first-order control on sedimentation and manganese metallogenesis, supporting a trinity model of tectonic control, hydrothermal fluid transport, and sedimentary enrichment. These insights not only improve our understanding of rift-related manganese formation in southeastern Yunnan but also offer a methodological framework applicable to similar rift basins worldwide. Full article

Gold is a vital strategic resource for many countries. The Laozhaiwan area is an important gold resource base in Yunnan Province and even nationwide. Conducting mineral resource exploration in this region to increase gold reserves is of great significance. The application of remote sensing technology in mineral resource exploration is a green and efficient technical approach, which has been widely utilized in the field of mineral resource prospecting. This study selects the Laozhaiwan area in the southeastern part of Yunnan Province as the research region. Linear and ring structures were extracted using the remote sensing visual interpretation method based on Sentinel-2A multispectral data. Additionally, Sentinel-2A, ASTER, and ZY1-02D data were used to extract iron-stained, hydroxyl, silicification, and limonite alteration information through Principal Component Analysis (PCA) and Spectral Angle Mapper (SAM) methods. Additionally, 50 linear structures and 12 ring structures were extracted. A comprehensive analysis of geological data reveals that alteration minerals and linear-ring structures are closely related to mineralization, providing valuable indicators for mineral resource exploration. By comprehensively analyzing the alteration information and remote sensing interpretation results of the linear-ring structures, two prospective areas for mineral exploration were delineated. Field investigations and petrographic studies confirmed the reliability of remote sensing technology in mineral exploration. The mineral exploration method based on multi-source remote sensing technology can clearly reflect various alteration information and linear-ring structural data. It provides remote sensing geological insights for geological survey work and has great application potential in the field of mineral resource exploration. Full article

The Dulong deposit in Wenshan, southeastern Yunnan Province, is rich in zinc, tin, and copper resources, accompanied by rare metals such as indium and silver. It is a particularly important indium production base, with reserves of approximately 7000 tons, ranking first globally. Enrichment and recovery of indium-bearing minerals are mainly achieved through mineral processing technology. However, the recovery rate of indium in the Dulong concentrator remains relatively low, and there is an insufficient understanding of its occurrence state and distribution characteristics, resulting in marked indium resource wastage. Here, we conducted a systematic process mineralogy study on indium-bearing polymetallic ore in the Dulong concentrator. The average grade of indium in the ore is 43.87 g/t, mainly occurring in marmatite (63.63%), supplemented by that in silicate minerals (23.31%), chalcopyrite (7.84%), and pyrrhotite (4.22%). The indium has a relatively dispersed distribution, which is inconducive to enrichment and recovery. The substitution mechanism of indium in marmatite was investigated using laser ablation inductively coupled plasma mass spectrometry. This revealed a positive correlation between indium and copper, allowing us to revise the substitution relationship to: ${\mathrm{Zn}}_x\mathrm{S}+{\mathrm{Cu}}^{+}+{\mathrm{In}}^{3+}\to {\mathrm{Zn}}_{\mathrm{x}-2}\mathrm{CuInS}+2{\mathrm{Zn}}^{2+}$ or ${\mathrm{Zn}}_{\mathrm{x}-1}\mathrm{FeS}+{\mathrm{Cu}}^{+}+{\mathrm{In}}^{3+}\to {\mathrm{Zn}}_{\mathrm{x}-2}\mathrm{CuInS}+{\mathrm{Zn}}^{2+}+{\mathrm{Fe}}^{2+}$. Electron probe microanalysis revealed the presence of roquesite (CuInS₂), an independent indium mineral not previously reported from this deposit. Our detailed investigation of the Dulong concentrator mineral processing technology showed that the recovery rate of indium from marmatite is currently poor, at only 48.01%. To improve the comprehensive utilization rate of indium resources, it will be necessary to further increase the recovery rate from marmatite and explore the flotation recovery of indium from chalcopyrite and pyrrhotite. Full article

The Duobaoshan mineralization area in Heilongjiang Province is a key copper–molybdenum–gold polymetallic region in China. Its southeastern Fudiyingzi–Bacheli area, located at the intersection of the NW-trending copper and NE-trending gold belts, exhibits favorable mineralization conditions. Despite over 70 years of placer gold mining and the discovery of one small copper deposit and one gold deposit, the area remains underexplored with significant peripheral exploration potential. This study integrates 1:50,000 geological mapping, high-precision magnetic surveys, phase-induced polarization, and soil geochemistry through multi-source data fusion for comprehensive mineral prediction. Key steps include delineating Cu, Au, and Mo anomalies and analyzing their associations with Zn, Cd, Ag, As, etc.; inferring NE-, NW-, and near-EW-trending linear structures via magnetic boundary enhancement; dividing high/low resistivity zones and identifying nine significant and six weak phase anomalies using phase-induced polarization; establishing a mineralization model based on typical deposits; and delineating four priority exploration targets. These results provide a scientific basis for further exploration in shallow coverage areas. Full article

This study analyzes the ore potential of the tectono-stratigraphic zones in the Shyngys-Tarbagatai folded system using metallogenic diagrams. These diagrams condense extensive geological and metallogenic data, illustrating stratified and intrusive formations, formation types, depositional environments, and ore loads in chronological sequence. The analysis highlights variations in ore mineralization intensity across the zones, identifying both highly and less ore-bearing areas. Most zones show polymetallic mineralization with 2 to 12 types of minerals; gold and copper are present in all zones. Temporal analysis identified key productive levels in the Late Ordovician, Early Silurian, and Early Devonian, corresponding to active stages of island arcs, forearc and backarc basins, and the Devonian volcanic–plutonic belt. The structures of the Shyngys-Tarbagatai folded system are classified as island-arc structures of active continental margins. Comparing the ore potential of its tectono-stratigraphic zones with similar modern structures shows that, except for the Maikain zone, all others have significantly lower ore potential. The obtained data is most likely a result of the region’s poor exploration coverage. As such, future efforts should prioritize further investigation of the identified mineralization zones. This is evident from the dominance of small, medium, and large deposits, and ore occurrences in all tectono-stratigraphic zones when assessing their ore potential. Preliminary analysis of the ore potential in the tectono-stratigraphic zones of the Shyngys-Tarbagatai folded system, based on metallogenic diagrams, clearly supports the need for regional and exploration studies. These should focus on poorly explored stratigraphic levels, ore-bearing geological formations, and geodynamic settings that are favorable for deposit formation. This will provide a more accurate assessment of the potential in these zones. Full article

The Yidun island arc was formed in response to the Late Triassic westward subduction of the Ganzi–Litang oceanic plate, a branch of the Paleo-Tethys Ocean. The Zhongdian arc, located in the south of the Yidun island arc, has relatively large number of porphyry (skarn) type Cu–Mo ± Au polymetallic deposits, the largest of which is the Pulang Cu (–Mo–Au) deposit with proven Cu reserves of 5.11 Mt, Au reserves of 113 t, and 0.17 Mt of molybdenum. However, the relationship between mineralization and the potassic alteration zone, phyllic zone, and propylitic zone of the Pulang porphyry deposit is still controversial and needs further study. Titanite (CaTiSiO₅) is a common accessory mineral in acidic, intermediate, and alkaline igneous rocks. It is widely developed in various types of metamorphic rocks, hydrothermally altered rocks, and a few sedimentary rocks. It is a dominant Mo-bearing phase in igneous rocks and contains abundant rare earth elements and high-field-strength elements. As an effective geochronometer, thermobarometer, oxybarometer, and metallogenic potential indicator mineral, titanite is ideal to reveal the magmatic–hydrothermal evolution and the mechanism of metal enrichment and precipitation. In this paper, major and trace element contents of the titanite grains from different alteration zones were obtained using electron probe microanalysis (EPMA) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to define the changes in physicochemical conditions and the behavior of these elements during the process of hydrothermal alteration at Pulang. Titanite in the potassic alteration zone is usually shaped like an envelope. It occurs discretely or is enclosed by feldspar, with lower contents of CaO, Al, Sr, Zr and Hf; a low Nb/Ta ratio; high ∑REE + Y, U, Th, Ta, Nb, and Ga content; and high FeO/Al₂O₃ and LREE/HREE ratios. This is consistent with the characteristics of magmatic titanite from fresh quartz monzonite porphyry in Pulang and other porphyry Cu deposits. Titanite in the potassium silicate alteration zone has more negative Eu anomaly and a higher U content and Th/U ratio, indicating that the oxygen fugacity decreased during the transformation to phyllic alteration and propylitic alteration in Pulang. High oxygen fugacity is favorable for the enrichment of copper, gold, and other metallogenic elements. Therefore, the enrichment of copper is more closely related to the potassium silicate alteration. The molybdenum content of titanite in the potassium silicate alteration zone is 10²–10⁴ times that of the phyllic alteration zone and propylitic alteration zone, while the copper content is indistinctive, indicating that molybdenum was dissolved into the fluid or deposited in the form of sulfide before the medium- to low-temperature hydrothermal alteration, which may lead to the further separation and deposition of copper and molybdenum. Full article

This study considers the features of the chemical composition, internal structure, and oscillatory zoning of sulfosalts and sulfates in the epithermal high–intermediate-sulfidation-type Au-Ag-Te Emmy deposit (Khabarovsk Territory, Russia). In Emmy deposit, sulfosalts primarily represent goldfieldite, probably corresponding to a high-sulfidation (HS) mineral association replaced bytennantite–tetrahedrite group minerals. The latter is associated with tellurides and native tellurium, corresponding to an intermediate-sulfidation (IS)-type ore assemblage and suggesting an increasing influx of Te, Sb, and As in the system. Goldfieldite is replaced by native tellurium and tellurides along its growth zones, and is characterized by oscillatory zoning. The replacement of goldfieldite by mercury, nickel, lead, and copper tellurides indicate a new influx of native gold, native tellurium, and gold–silver tellurides into the open mineral-forming system. At deeper levels of the Emmy deposit, an advanced argillic alteration assemblage includes aluminum phosphate–sulfate (APS) minerals, represented by members of the svanbergite–woodhouseite series. Element mapping of the studied APS mineral grains indicated three distinct areas recording the evolution of the hydrothermal system in the Emmy: an oscillatory-zoned margin enriched in sulfur, lead, and barium, corresponding to the late influx of IS state fluids related to gold and tellurides; an intermediate part, which is leached and corresponds to the HS mineralization stage; and the central part of the grains, which is enriched in cerium, calcium, and strontium, resulting from a replacement of magmatic apatite in the pre-ore alteration stage. The leached zone between the core and rim of the APS grains is related to a change in crystallization conditions, possibly due to the mixing processes of the fluids with meteoric water. Barite, found in the upper level of the advanced argillic hypogene alteration assemblage, is also characterized by oscillatory zoning, associated with the enrichment of individual zones in lead. Micron gold particles associated with barite are confined to their lead-enriched zones. The study of fluid inclusions in quartz within the Emmy deposit showed the hydrothermal ore process at a temperature of 236–337 °C. Homogenization temperatures for quartz–pyrite–goldfieldite mineral association vary within 337–310 °C and salinity varies within 0–0.18 wt.%NaCl equivalent, and for gold–silver–telluride–polymetallic mineral association, they decrease and vary within 275–236 °C and salinity slightly increases from 0.18 to 0.35 wt.%NaCl equivalent. This study demonstrates that the nature of oscillatory zoning in sulfosalts and sulfates in the Emmy deposit results from an external process. Such a process is of fundamental importance from a genetic point of view. Full article

The Dapingzhang Cu-polymetallic deposit in Yunnan is a volcanic massive sulfide (VMS) deposit, located on the western edge of the Lanping–Simao block. Recently, gold-rich polymetallic orebodies with significant economic value have been discovered. However, the occurrence and enrichment mechanisms of the gold remain unclear. This study investigates the massive sulfide orebodies (V₁) through detailed geological surveys. Techniques such as optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron probe microanalysis (EPMA) were used to clarify the occurrence of gold, and to reveal the enrichment mechanisms. The genesis of the orebodies consists of three stages: (I) pyrite–quartz, (II) pyrite–chalcopyrite–sphalerite–galena–quartz, and (III) pyrite–chalcopyrite–sphalerite–galena–quartz–calcite. Gold precipitated during each of these mineralization stages, and it may be described as multiphase mineralization. Gold predominantly exists as invisible gold (≤0.1 μm), with minor visible gold as native gold and independent minerals (küstelite, electrum, calaverite). Invisible gold mainly occurs as gold microinclusions (Au⁺) in pyrite, chalcopyrite, and sphalerite. Combined with the previous research, comprehensive analysis determined that deep-circulating seawater, driven by a magmatic hydrothermal system, leaches and dissolves mineralizing materials from underlying volcanic rocks. The mineralizing fluid, mixed with magmatic fluid, migrates upward through volcanic conduits or is expelled to the seafloor. Changes in physicochemical conditions lead to the co-precipitation of gold and sulfides, forming a mineralization structure with lower channel facies and upper eruptive facies. Full article

Magnetic and electromagnetic techniques have a long history of application in mineral exploration to detect deposits and their surroundings. Their implementation over the last fifteen years has been affected by strong variations in the mining market in parallel with important technological developments. During this period, both methods were the subject of numerous documented case studies all over the globe, which is a sign of popularity and longevity of these techniques. Through a review of case histories from the main geophysical journals, we analyze the principal usage of these methods when applied to mineral exploration, while the majority of documented cases originate from North America, Asia, and Australia. There are more case studies describing the use of the magnetic method and we attribute this popularity to direct and indirect use of this method for mineral exploration. In particular, there is an increasing number of magnetic surveys conducted with drones. Combining magnetic and electromagnetic techniques is also common. The number of magnetic and EM technique case histories range by descending order from gold, porphyry copper, polymetallic, massive sulfides, uranium, Ni-Cu-PGE, iron ore, kimberlite, and iron-oxide copper-gold, with a number of single continent-specific applications. Full article

The 1500 km-long Gangdese magmatic belt is a crucial region for copper polymetallic mineralization, offering valuable insights into collisional porphyry copper systems. This study focuses on the Demingding deposit, a newly identified occurrence of molybdenum–copper (Mo-Cu) mineralization within the eastern segment of the belt. While the mineralization age, magmatic characteristics, and tectonic context are still under investigation, we examine the deposit’s petrology, zircon U-Pb geochronology, whole-rock chemistry, and Re-Os isotopic data. The Demingding deposit exhibits a typical alteration zoning, transitioning from an inner potassic zone to an outer propylitic zone, which is significantly overprinted by phyllic alteration closely associated with Mo and Cu mineralization. Zircon U-Pb dating of the ore-forming monzogranite porphyries reveals crystallization ages ranging from 21 to 19 Ma, which is indistinguishable within error from the mean Re-Os age of 21.3 ± 0.4 Ma for Mo veins and veinlets hosted by these porphyries. This alignment suggests a late Miocene magmatic event characterized by Mo-dominated mineralization, coinciding with the continuous thickening of the continental crust during the collision of the Indian and Asian continents. The ore-forming porphyries range in composition from granodiorite to monzogranite and are classified as high-K calc-alkaline with adakite-like features, primarily resulting from the partial melting of subduction-modified thickened mafic lower crust. Notably, the ore-forming porphyries exhibit higher fO₂ and H₂O levels than barren porphyries in this area during crustal thickening, highlighting the significant contributions of hydrous and oxidized fluids from their source to the Mo-Cu mineralization process. Regional data indicate that the Gangdese porphyry metallogenic belt experienced concentrated Cu-Mo mineralization between 17 and 13 Ma. The formation of Mo-dominated deposits such as Demingding and Tangbula in the eastern segment of the belt, with slightly older ages around 20 Ma, underscores the presence of a significant porphyry Mo metallogenic event during this critical post-collision mineralization period. Full article

Intermediate-acidic granites occur extensively in the Chazangcuo copper-lead-zinc mining area (hereinafter referred to as the Chazangcuo mining area) in Tibet, China. Exploring their rock types, sources, and tectonic settings is essential for understanding the genesis of granites in the region. This study investigated the petrology of the Chazangcuo granites, as well as the geochemical characteristics of their major elements, trace elements, and rare earth elements (REEs). Results indicate that the Chazangcuo granites are high-K calc-alkaline metaluminous rocks. These granites are enriched in large-ion lithophile elements (LILEs; e.g., Rb and Ba), depleted in high-field-strength elements (HFSEs; e.g., Nb, Ta, Zr, and Hf), with a relative enrichment in light rare earth elements (LREEs), and relatively depleted in heavy rare earth elements (HREEs), exhibiting a V-shaped distribution pattern and weak negative Eu anomalies. The granites are classified as typical I-type granites, displaying characteristics of crust-derived magmas with contributions from mantle sources and exhibiting significant fractional crystallization. The Chazangcuo granites were derived from the partial melting of mafic rocks, with protoliths formed in a moderate temperature environment. Influenced by the subduction of the Neotethys Ocean, the Chazangcuo granites were formed in an arc caused by the collision between the Indian and Eurasian plates (also referred to as the Indo–Eurasian collision) during the Late Triassic. Under the effect of geological activities such as upwelling of the asthenosphere and fluid intrusion and differentiation, metal mineralization was prompted to be distributed in the granite fissures, forming the Cu-Pb-Zn polymetallic deposits of Chazangcou in Tibet, suggesting that the granites are closely associated with mineralization. Full article

Porphyry and the associated skarn-type deposit is one of the most important types of ore deposits worldwide, which usually exhibit significant zoning of mineralization-alteration, but the research on element migration in these mineralization-alteration zones is relatively weak. The Beiya porphyry–skarn gold-polymetallic deposit is a super-large Cenozoic deposit located in the Sanjiang metallogenic belt, northwestern Yunnan, China. In this paper, through a detailed analysis of mineralization and alteration zoning and its element migration regularity, the findings are as follows: (1) Three types of hydrothermal alteration—porphyry alteration, contact alteration, and wall-rock alteration—are developed, and porphyry alteration includes potassic, phyllic, propylitic, and argillic alteration; (2) five types of mineralization—porphyry-type Cu–Au–(Mo), skarn-type Au–Fe–(Cu), hydrothermal vein-type Au–Fe, distal hydrothermal-type Pb-polymetallic, and oxidizing-leaching enriched-type Au—occur in a diversity of forms, which are dominantly controlled by structures and lithologies; (3) concentric-banded mineralization-alteration zones are exhibited centrally from the alkaline porphyry outward or upward, namely [porphyry alteration] potassic → phyllic → propylitic → argillic → [contact alteration] skarnitization–marbleization → [wall-rock alteration] marbleization–silicification–calcitization; (4) porphyry-type mineralization predominantly forms within potassic and phyllic zones, while skarn-type mineralization occurs in contact alteration zones, and proximal and distal hydrothermal (vein)-type mineralization are commonly distributed in marbleization–silicification–calcitization alteration zones; and (5) element migration analysis demonstrates a significantly lateral and vertical zoning in the metallogenic element association of Cu–Mo → Cu–Au → Au–Fe–Cu → Au–Fe → Pb–Zn–Au–Ag–Fe from alkaline porphyry outward to the wall-rock. The mineralization-alteration zoning model indicates the Beiya deposit has similar mineralization and alteration zone characteristics to the typical porphyry copper system; and element migration within mineralization-alteration zones provides new scientific information for understanding the metallogenic regularity and prospecting at Beiya, as well as the similar types of deposits in the Sanjiang metallogenic belt and elsewhere in the world. Full article

Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe₂O₃) compared to the historical slags (up to 26.1 wt% of Fe₂O₃). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management. Full article

The results of studies on the content of aluminum and heavy metals in benthic sediments and algae in the estuaries of the Arctic island Vaygach are presented. This island is located on the Barents and Kara Sea border, and it is part of the Pay-Khoi ridge which can be called a “continuation” of the Ural Mountains to the north. The observations were conducted in Krasnaya and Varkulyakha Rivers located in the island’s southern part and flow into the Yugorsky Shar Strait. Krasnaya River is located near a polymetallic ore deposit, which was developed in 1931–1934. Reconnaissance fieldwork was carried out in the river estuaries through measurements of salinity and water level. Measurements of the mass concentration of elements in the studied samples of sediments and algae were carried out by atomic emission spectrometry. The preparation of plant samples was by microwave decomposition, and that for samples of bottom sediments was carried out by acid decomposition in an open manner. The obtained concentration samples were compared using “Tukey exploratory data analysis (EDA)”. The presence of anomalies in the high content of copper, manganese, and zinc in filamentous algae at the control site in the Krasnaya River estuary was revealed. For some elements, the enrichment index was calculated relative to the upper part of the earth’s crust content. It is assumed that the occurrence of this situation is due to the long-term consequences of mining polymetallic ores. The accumulation of metals in river estuaries may be related to the observed warming of the climate in the western sector of the Arctic region. Full article

Geochemical measurements of stream sediments are practical for small-scale mineral exploration. However, traditional grid interpolation methods cause element concentrations to diffuse and smooth out anomalies, particularly in complex terrains, making it challenging to reflect the actual distribution of elements accurately. We applied the Dynamic Enhanced Weighted Drainage Catchment Basin (DE-WDCB) method to enhance the retention and identification of local anomalies by limiting the scope of analysis to specific drainage units. This method reduces interference from varying background values across different watersheds, effectively enhancing geochemical element anomalies and aligning better with geomorphic conditions. The DE-WDCB method was tested in the Duobaoshan–Heihe area, a significant copper polymetallic mineral district in northeastern China. Compared with traditional grid interpolation methods, the DE-WDCB method retained and strengthened low and weak abnormal information of favorable mineralization elements, particularly in the Luotuowaizi area. The method demonstrated a higher spatial coverage rate with mineral points and a more vital ore-indicating ability. Specifically, the DE-WDCB method identified anomalies with a mean accuracy of 63.57% (p < 0.05, 95% CI: 47.64%–79.50%), compared to 50.53% for traditional methods. In conclusion, in regions with a complex topography and watershed differences, the DE-WDCB method effectively reduces local geochemical background interference, accurately identifies low and weak geochemical anomalies, and better reflects the actual distribution of elements. This makes it a significantly advantageous method for geochemical anomaly extraction, delineating higher-confidence exploration targets in the Sandaowan–Luotuowaizi area in the east and the triangular area between Duobaoshan, Yubaoshan, Sankuanggou, and the midstream highlands of the Guanbird River in the west. Full article