Main Alteration Types Research Articles

CYFIP2 serves as a prognostic biomarker and correlates with tumor immune microenvironment in human cancers

BackgroundThe mechanisms whereby CYFIP2 acts in tumor development and drives immune infiltration have been poorly explored. Thus, this study aimed to identifying the role of CYFIP2 in tumors and immune response.MethodsIn this study, we first explored expression patterns, diagnostic role and prognostic value of CYFIP2 in cancers, particularly in lung adenocarcinoma (LUAD). Then, we performed functional enrichment, genetic alterations, DNA methylation analysis, and immune cell infiltration analysis of CYFIP2 to uncover its potential mechanisms involved in immune microenvironment.ResultsWe found that CYFIP2 significantly differentially expressed in different tumors including LUAD compared with normal tissues. Furthermore, CYFIP2 was found to be significantly correlated with clinical parameters in LUAD. According to the diagnostic and survival analysis, CYFIP2 may be employed as a potential diagnostic and prognostic biomarker. Moreover, genetic alterations revealed that mutation of CYFIP2 was the main types of alterations in different cancers. DNA methylation analysis indicated that CYFIP2 mRNA expression correlated with hypomethylation. Afterwards, functional enrichment analysis uncovered that CYFIP2 was involved in tumor-associated and immune-related pathways. Immune infiltration analysis indicated that CYFIP2 was significantly correlated with immune cells infiltration. In particular, CYFIP2 was strongly linked with immune microenvironment scores. Additionally, CYFIP2 exhibited a significant relationship with immune regulators and immune-related genes including chemokines, chemokines receptors, and MHC genes.ConclusionOur results suggested that CYFIP2 may serve as a prognostic cancer biomarker for determining prognosis and might be a promising therapeutic strategy for tumor immunotherapy.

Genesis of the Jinji gold deposit in the Jiangnan Orogen, South China: Constraints from geology, chlorite geochemistry, age and H-O-S-Pb isotopes

The Jinji gold deposit (northeastern Hunan province) is located in the central Jiangnan Orogenic Belt, South China. The auriferous sulfide-calcite-quartz vein orebodies, controlled by near NNW-trending faults, occur in the Lengjiaxi Group metamorphic rocks spatially associated with the Banshanpu granitic pluton. Metallic minerals include mainly pyrite, arsenopyrite, and pyrrhotite, with minor sphalerite, chalcopyrite, galena, and native gold. The main alteration types include K-feldspar, silicic, sericite, carbonate, and chlorite. The gold mineralization comprises three stages: (1) quartz–K-feldspar–chlorite–carbonate–arsenopyrite–pyrite, (2) quartz–carbonate–chlorite–polymetallic, and (3) quartz–carbonate–fluorite–pyrite. Geothermometry of chlorite yielded formation temperatures of 261–332 °C (stage 1) and 262–290 °C (stage 2), whereas the calculated oxygen fugacity of chlorite is −45 to −40 (stage 1) and −42 to −39 (stage 2). The δ18OH2O and δD values are 8.8–10.5 ‰ and −73.3 to −72.8‰ (stage 1), 3.2–4.8 ‰ and −83.6 to −80.7‰ (stage 2), and −1.4 to −0.4 ‰ and −82.2 to −78.6‰ (stage 3), respectively. These results indicate that the primary ore fluids (stages 1 and 2) were derived from a granitic magma and were mixed with meteoric water in stage 3. The gold-bearing sulfides (pyrite, pyrrhotite and galena) have δ34S values of −4.8 to +5.8‰, whilst their 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios are of 35.975–36.204, 15.160–15.231, and 16.100–16.176, respectively. The sulfide S-Pb isotope compositions indicate that the metals were likely derived from the Banshanpu granitic magma, which was produced by partial melting caused by Early Paleozoic crustal thickening. The Jinji deposit exhibits many features of orogenic gold mineralization, such as the ore-controlling structures and mineralization styles (quartz-calcite-sulfide veins). The Jinji deposit is the first reported gold deposit in the central Jiangnan orogen with a genetic link to early Paleozoic granitic magma.

Magnetite‐fluorapatite geochemistry and monazite U–Pb geochronology of the Mohuldih uranium deposit, Singhbhum Shear Zone, eastern India

In this study, textural relations coupled with mineral chemistry of hydrothermal magnetite, fluorapatite, monazite and allanite from the Mohuldih uranium deposit in the Singhbhum Shear Zone (SSZ) is used to characterize the nature of the fluid during various events of alteration and uranium precipitation. These minerals have two distinct textural types, the earlier of which are coeval with the uraninite mineralization. The later type formed during subsequent hydrothermal overprint as a result of coupled dissolution‐reprecipitation of earlier fluorapatite and mobilization of light rare earth elements. Uranium‐lead dating of texturally‐constrained hydrothermal monazite grains yields two major concordant age clusters at 1855 ± 7 Ma and 963 ± 10 Ma and several discordant analyses. Two spot analyses furnish concordant ages of 1656 ± 33 Ma and 1438 ± 35 Ma that are identical within error of the 207Pb/206Pb ages (1628–1643 Ma and ca. 1392 Ma) of several discordant data points. Similar ages have been reported by other studies from the rocks of the SSZ and are therefore considered to be geologically meaningful. The oldest age of ca. 1855 Ma obtained from the texturally early core regions of monazite corresponds to the earliest stage of uraninite mineralization. The two main alteration types can be interpreted based on the known metamorphic events in the SSZ. A combination of high‐temperature calcic iron ± sodic and high‐temperature potassic iron alteration accompanied the M1 metamorphic event and the low‐temperature silicification/K‐Al alteration during the M2 metamorphic event. A comparative study between our data on magnetite and fluorapatite compositions with those from global iron oxide‐Cu‐gold (IOCG) and iron oxide‐apatite deposits classifies Mohuldih as an IOCG‐type deposit.

Geochemical Conditions and Factors Controlling the Distribution of Major, Trace, and Rare Elements in Sul Hamed Granitic Rocks, Southeastern Desert, Egypt

Egypt is mainly covered by ophiolitic rocks, muscovite, and two mica granites, in addition to different types of acidic and basic dikes. Our field observations indicated that El Sela granites were subjected to alteration types such as silicification, kaolinization, and hematitization, which is associated with uranium mineralization. Petrographic investigations clarified that these rocks were affected by saussiritization, muscovitization, and silicifications as the main alteration types associated with uranium mineralization (uranophane and autunite). We carried out chemical analyses of our samples for major oxides and trace and rare earth elements using ICP-OES and ICP-MS. The studied altered granites had high silica, titanium, and phosphorous as major components, with enhanced amounts of trace elements such as Nb, Ta, Zn, Mo, Pb, and Re, in addition to REE, especially light ones. The average REE content was higher than that of worldwide granites with LREE enrichment. One sample had a strong M-type tetrad effect in the fourth type; other samples had weak W-type in the third type, indicating the effect of hydrothermal alteration processes in the altered granites. This was confirmed by calculating the ratios of most isovalents that deviated from the chondritic ratio in many values. Variation diagrams of U and some trace elements illustrated that U had a weak positive correlation with Y and a strong positive correlation with gold, while it had weak to moderate negative correlation with Hf and Zr/U. In addition, uranium had a weakly defined correlation with the other trace elements, indicating a weak to moderate effect of magmatic processes, while the post-magmatic processes surficial or underground water greatly influenced the redistribution of uranium and other elements.

Hydrothermal Alteration Mapping Using Landsat 8 and ASTER Data and Geochemical Characteristics of Precambrian Rocks in the Egyptian Shield: A Case Study from Abu Ghalaga, Southeastern Desert, Egypt

This study evaluates the geological attributes of rocks within the Abu Ghalaga area using spatial, geochemical, and petrographic approaches. ASTER and Landsat imagery processed using band ratio and principal component analysis were used to map hydrothermal alterations, while a regional tectonic evaluation was based on automated extraction of lineaments from a digital elevation model. Geochemical and petrographic analyses were then employed for discrete scale evaluation of alteration patterns of rocks across the study location. Based on satellite image processing, alteration patterns across the study area are widespread, while evidence from lineament analysis suggests a dominant NW–SE tectonic trend accompanied by a less dominant ENE–WSW direction. The different rock units exposed in the studied district are arranged chronologically from oldest to youngest as arc metavolcanic group (basalt and rhyolite), arc metagabbro–diorite, gneissose granite (granodiorite and tonalite), and dykes (aplite and felsite). Various types of igneous and metamorphic rocks have propylitic, phyllic, and argillic zones. Geochemical data indicate that the studied rocks are classified into granite, granodiorite, gabbroic diorite, and gabbro. Geochemically, the rocks have a sub-alkaline magma type. The granodiorite–tonalite is derived from the calc–alkaline magma nature, while gabbro and diorite samples exhibit tholeiitic to calc–alkaline affinity. The tectonic setting of the studied rocks trends toward volcanic arc granite (VAG). Based on petrographic, geochemical, and remote analyses, sericitization, chloritization, epidotization, kaolinitization, carbonatization, and silicification are the main alteration types present in the study area. As a result of lineaments analysis, the existing fractures and structural planes form valid flow paths for mineral-bearing hydrothermal solutions.

Delineation of the porphyry-skarn mineralized zones (NW Turkey) using concentration–volume fractal model

This study is carried out for delineation of the Tepeoba porphyry-skarn Cu-Mo ± Au mineralized zones at the Biga peninsula (NW Turkey) using the concentration–volume (C–V) fractal model. The power-law C–V relationships of Cu, Mo, and Au reveal five mineralized zones of Cu, three zones of Mo, and five zones for gold in the Tepeoba deposit. The main phase of the mineralization has average ore grades of 0.257% Cu, 0.357% Mo and 5.3083 ppm Au. Cu–Mo sulfide-rich hypogene ore zone overlain by mineralized oxidation zone are encompassed by three main alteration types, which are represented by biotite ± muscovite-K-feldspar, actinolite-albite and outer chlorite-epidote-calcite mineral associations occurring within the porphyritic microgranite and hornfels in the mine area. The delineated mineralization trend, based on the C–V fractal model, suggested that Cu and Mo enrichment zones were controlled by the same geochemical processes in the deposit due to their similar trends with the C–V log-log plot. Cu and Mo occurred mainly within the breccia zones along with stockwork veining at the contact between the hornfels and the biotite (±muscovite)-K-feldspar-altered Eybek microgranite. The main mineralization zone of Au developed in the oxidation zone due to of supergene enrichment processes.

Characteristics of fluid inclusions in the Cenozoic volcanic-hosted Kushk-e-Bahram Manto-type Cu deposit of central Iran

Abstract The Kushk-e-Bahram Manto-type Cu deposit is located in central Iran, within Eocene to Oligo–Miocene volcanic strata which occur in the central part of the Uremia-Dokhtar Magmatic Arc (UDMA). Propylitization, silicification, argillization and carbonatization are the main types of alteration to have affected the pyroclastic and volcanic rocks. There are high amounts of oxide minerals, including malachite, azurite, hematite, magnetite and goethite. Three types of primary FIs have been determined in the Kushk-e-Bahram deposit, namely; I: two-phase liquid-rich FIs (L+V), II: mono-phase liquid FIs, III: two-phase vapour-rich FIs which have been identified based on petrographical studies. Based on FI studies of co-existing quartz and calcite, homogenization temperatures (Th) must have been between 67 and 228°C, with an average of 158°C. Moreover, salinity is between 14.0–30.3 wt% NaCl, equivalent to a 19.6% average. Fluid density values vary from 0.8 to 1.1 gr/cm3. Based on FI data and related diagrams, the depth of their trapping was estimated to be <200 m and ore formation occurred at pressures of <50 bars. Consequently, mineralogy, host rock and FIs characteristics in the Kushk-e-Bahram deposit are similar to the Manto-type Cu deposits in Mesozoic-Cenozoic volcanic belts of Iran and South America.

Geology, geochemistry, geochronology and genesis of the late Miocene porphyry Cu-Au-Mo mineralization at Afyon-Sandıklı (AS) prospect, western Anatolia, Turkey

Afyon-Sandıklı ‘AS’ is an example of a porphyry Cu-Au-Mo systems hosted in post-collisional late Miocene magmatic rocks within the Afyon-Ören Zone of Turkey. The systems were generated by multi-phase intrusions emplaced into early stage volcanic and volcanoclastic rocks of the Afyon volcanics. The REE and radiogenic isotope data from these rocks suggest a magma source containing residual garnet with a low hydrous phase. These collectively, favor a metasomatized mantle source for magmas generated in either subduction or post-collisional environments.Four main alteration types have been identified in the AS porphyry Cu prospect; potassic, phyllic, epidote-chlorite and advanced argillic. The alteration zones are centered around monzonite porphyry intrusives. Chalcopyrite and bornite are the main copper minerals in the potassic alteration zone with subordinate molybdenite. All are replaced by pyrite.The U-Pb SHRIMP analyses on a post-mineral micromonzonite porphyry dike yielded an age of 10.97 ± 0.09 Ma, whereas the host monzonite porphyry yielded an age range between 10.5 and 12.5 Ma. Ar-Ar geochronology on alunite constrains the timing of the argillic alteration at 11.2 ± 0.5 Ma.Fluid inclusion studies were performed on primary inclusions in quartz veins from the potassic and phyllic alteration zones. The primary fluid inclusions in quartz veins in both zones were classified as Type 1, single-phase vapor (V); Type 2, two-phase liquid-vapor (L-V); and Type 3, three-phase liquid-vapor-solid (L-V-S). Type 3 inclusions in the potassic alteration zone with weak phyllic overprint have higher homogenization temperatures compared to those in pervasive phyllic alteration zones. The majority group of fluid inclusions in the AS prospect are Type 2 inclusions with variable vapor and liquid abundances. This suggests boiling (phase separation) of the hydrothermal fluids, and post boiling trapping of the vapor and liquid. The presence of abundant multiphase (Type 3) inclusions in the AS prospect marks the stage when phase separation took place. The phase separation appears to have resulted in intermediate to high-salinity multiphase brines and daughter crystals in the residual fluid. Additionally, we suggest that superposition of phyllic and potassic alteration zones with a variety of Type 2 and Type 3 inclusions in the AS prospect should mark the stage at which mixing by relatively cooler and dilute meteoric water coupled with phase separation occurred.The calculated δ18O(fluid) vs δD(fluid) values for the alteration minerals display a wide range between the primary magmatic field to the meteoric water line. The δ18O(fluid) vs δD(fluid) values for biotite suggest a strong magmatic water influence during the formation of potassic alteration. Likewise, a very narrow range of δ34S, close to the sulfur isotope values of magmatic sulfur indicate a magmatic source, and may suggest that potassic alteration was caused by a uniform magmatic fluid source. Additionally, the enrichment in the δD(fluid) from biotite suggests that phase separation (boiling) was also active during potassic alteration. The overlapping pattern of the δ18O(fluid) vs δD(fluid) compositions for biotite and sericite indicate an isotopic similarity, and may suggest that they have been formed from a similar, predominantly magmatic fluid mixed to some degree with the meteoric water.

Structural and Geochemical Characterization of Gold Mineralized Quartz Veins in Belikombone Gold Prospect, Betare-oya Gold District, East Cameroon

Au-bearing quartz veins in the Belikombone area are confined to major NW-SE orientations in schists and N-S and ENE – WSW in other host rocks. The objectives of this work were to study field, mineralogy and geochemical characteristics of gold mineralised quartz veins. Schists (chlorite rich) and gneisses (moderately magnetic) are the dominant rock types in the area with granite occurring as intrusions within the gneisses. Gold-bearing quartz veins occur in association with metamorphosed rocks ranging in composition from quartz ± gold to those that contain quartz ± gold ± sulphides ± iron-oxides ± sericite and mafic minerals. The mineralized veins contain Au from 0.50 to 25 ppm, while the quartz veins considered barren contain 0.20 ppm Au. The concentration of As in the quartz veins ranges from 0.30ppm to 10.70 ppm and it show positive correlation with Au in samples with high Au concentration. The ΣREE varies from 5.79 to 173.64 in the quartz veins. The investigated veins show evidence of multiphase deformation and it is associated with D₂ deformation in the area. This structural setting suggest that the emplacement of gold mineralization occurred during the late Pan African orogeny. The main alteration types are silification, sericitization and sulphidation processes.

Analysis of rock alteration in a hydropower engineering project, southeastern China

The characteristics of rock and mineral alteration of a rock mass related to a hydropower engineering project in southeastern China are analyzed and presented. Rock mass alteration is an important engineering geology challenge in the region; in this study, it is shown that the main types of alteration are albitization and formation of clay minerals. The main minerals in the altered rocks are plagioclase, K-feldspar, montmorillonite, illite, and kaolinite and the alteration processes were tracked using the interrelationships between K, Na, Ca, and loss on ignition during formation of illite, montmorillonite, and kaolinite. Laboratory testing of rock physical properties showed that water content, natural water absorption, and saturated water absorption in the altered rocks all gradually increase as the degree of alteration increases. However, rock mass density shows a decreasing trend with increasing alteration, and the degree of alteration exerts little influence on rock particle density. Rock disintegration tests show that the disintegration index decreases as alteration deepens.

Geochemistry, fluid inclusions and sulfur isotopes of the Govin epithermal Cu-Au mineralization, Kerman province, SE Iran

Govin area is located southeast of the Urmieh-Dokhtar volcano- plutonic arc, which formed as the result of subduction of the Neo-tethyan oceanic crust beneath the central Iran continent. The arc hosts world-class Sar-Cheshmeh Cu porphyry deposit and many other Cu, Cu-Mo, Cu-Au porphyry, and Cu-Zn-Pb-Ag-Au skarn and epithermal deposits. The rock units in the Govin area include Eocene volcaniclastic rocks that intruded by post-Miocene hypabyssal quartz-monzonite, grano-diorite, diorite and quartz-diorite stocks. The stream sediment geochemical surveys display Cu, Au, Mo, Bi, Sb, Pb and As anomalies. The lithogeochemical prospecting in anomaly checking stage identified quartz veins with considerable abundances of Cu (2.98%) and Au (2.41 ppm). The ore-bearing quartz veins classify into quartz + iron oxides ± gold and quartz + sulfide ± gold. The dominant structural trend of vein systems is 60°–70° (NE-SW), with dips from 75° NW to vertical that cut altered andesite, porphyritic andesite, basaltic andesite and tuff. Mineral associations are quartz, adularia, chalcopyrite, pyrite, bornite, galena, sphalerite, as well as chalcocite, covellite, malachite, iron oxides and hydroxides in oxidized zones. Hydrothermal alteration is generally well-developed surrounding the ore-bearing systems. The main types of alterations in the area include propylitization, phyllic, and argillic associated with silicification. Fluid inclusions studies on quartz grains separated from mineralized veins exhibits the melting temperature of ice (Tm ice) values range from −12 to −1 °C corresponding to salinities of 2.5 to 37.04 wt% NaCl equiv. The superfluity LV fluid inclusions have salinity of 2.47 to 15.96 wt% NaCl equiv. The homogenization temperature of LV, VL and LVS fluid inclusions range from 146 to 366 °C, 405 to 425 °C and 236 to 270 °C, respectively. The fluid inclusions observations reveal that both dilution and boiling of fluids were important in the deposition of metals in the Govin. The δ34SCDT of pyrite and chalcopyrite grains associated with mineralized quartz veins range from −2.13‰ to −8.54‰ that indicate sulfur originated from host volcanic-sedimentary series in the area. The Cu-Au bearing quartz veins in the Govin area are classified as low-sulfidation epithermal system, located in closed association with the Sar-Cheshmeh and Darreh-Zar porphyry copper deposits.

Geochemistry and petrography of REE-bearing Fe-oxide assemblages in Choghart iron deposit, Yazd, Iran

The Choghart magnetite-apatite deposit situated in the Bafq district, Central Iran, has been scrutinized for rare earth elements (REEs) by precise geochemical investigation. The Central Iran is a susceptible area of rare earth elements. One of the Choghart’s prominent points is the existence of hydrothermal zones which made prediction of REEs occurrence within the deposit possible. Choghart is placed within felsic volcanic tuffs, rhyolitic rocks, and volcanic sedimentary sections belonging to the lower Cambrian. Abundance and distribution pattern of REEs in Choghart iron deposits reveal a part of deposit formation and its mineralogical modifications. Petrography and mineralogy of the ore body demonstrated two main types of alterations (sodic and calcic) associated with iron ore mineralization in Choghart deposit. The main ore includes a large quantity of massive magnetite in the lower part of Choghart deposit. The minor mineralization involves apatite, pyrite, alkaline amphibole, especially actinolite and tremolite, calcite, talc, quart, monazite, and bastnasite. Geochemical sampling from north–northeast (N-NE) side of the mine denotes the presence of these elements in hydrothermal zones. Statistical populations of the area were categorized by fractal geometry into four main differentiations: host rock type (albitofyre), iron, metasomatose, phosphate zones, and a subset of the phosphate zone which is named high iron high phosphate type. REEs like lanthanum, neodymium, yttrium, and niobium constitute the most quantity of Choghart. Deposit characteristics demonstrate its similarity to Kiruna type. The significant feature of iron oxide-apatite deposits of Kiruna ore type is the existence of monazite inclusions within apatite. These inclusions were also observed within apatite type I and II of Choghart mineralization. Moreover, REEs geochemistry in Choghart deposit was identified by investigation on geochemical data analyses. The analysis represents negative Eu anomaly and further enrichment of light REEs compared to the heavy ones. Chondrite normalized REEs patterns are defined by negative anomalies of Eu, which is the main characteristic of Kiruna ore type. The results showed that REEs concentration in phosphate zone, as a high absorption of REEs, is much higher than metsomatose, albitofyre, and iron zones. REEs distribution in N-NE side of the mine indicated that the contact of iron ore with tailings in N-NW side of the mine leads REEs to be enriched nearly 1% , as well as that of NE with high contents of REEs 1.5% ), which is very significant.

The Chahnaly Low-Sulfidation Epithermal Gold Deposit, Western Makran Volcanic Arc, Southeast Iran

The Chahnaly low-sulfidation epithermal Au deposit and nearby Au prospects are located northwest of the intermittently active Bazman stratovolcano on the western end of the Makran volcanic arc, which formed as the result of subduction of the remnant Neo-Tethyan oceanic crust beneath the Lut block. The arc hosts the Siah Jangal epithermal and Kharestan porphyry prospects, near Taftan volcano, as well as the Saindak Cu-Au porphyry deposit and world-class Reko Diq Cu-Au porphyry deposit, near Koh-i-Sultan volcano to the east-northeast in Pakistan. The host rocks for the Chahnaly deposit include early Miocene andesite and andesitic volcaniclastic rocks that are intruded by younger dacitic domes. Unaltered late Miocene dacitic ignimbrites overlie these rocks. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon geochronology data yield ages between 21.8 and 9.9 Ma for the acidic-intermediate regional volcanism. The most recent volcanic activity of the Bazman stratovolcano involved extrusion of an olivine basalt during Pliocene to Quaternary times. Interpretation of geochemical data indicate that the volcanic rocks are synsubduction and calc-alkaline to subalkaline. The lack of a significant negative Eu anomaly, a listric-shaped rare earth element pattern, and moderate La/Yb ratios of host suites indicate a high water content of the source magma. Gold and electrum are temporally and spatially related to a series of structurally controlled, 030°-trending, subvertical hydrothermal breccias with chalcedony-adularia that cut porphyritic andesite and andesitic volcaniclastic rocks. Gold is associated with pyrite, a siliceous matrix of hydrothermal breccia, and previously formed vein clasts, as well as with iron oxides and hydroxides in oxidized zones. Rare silver minerals include Ag-bearing electrum and naumannite, iodargyrite, an unnamed silver diiodide, and hessite. Hydrothermal alteration is generally well developed surrounding the ore-bearing hydrothermal breccia. The main types of alteration in the area include an inner ~0.5- to 20-m-thick gold-bearing hydrothermal breccia composed of quartz-chalcedonyadularia-illite-pyrite, a ~5- to 50-m-thick zone of quartz, chalcedony, pyrite, illitic phengite, phengite, illitic muscovite, illite, illitic paragonite, paragonite, muscovite, montmorillonite and, rarely, siderite, and a 30- to 70-m outer propylitic zone of Fe-Mg chlorite, calcite, ankerite, dolomite, epidote, palygorskite, and pyrite. The Chahnaly Au deposit formed during the early stages of magmatism. LA-ICP-MS zircon U-Pb geochronology of host andesite and 40Ar/39Ar dating of two samples of gold-associated adularia show that the ore-stage adularia (19.83 ± 0.10 and 19.2 ± 0.5 Ma) is younger, by as much as 1.5 million years, than the volcanic host rock (20.32 ± 0.4 Ma). Therefore, either hydrothermal activity continued well after volcanism or a second magmatic event rejuvenated hydrothermal activity. This second magmatic event may be related to eruption of porphyritic andesite at ~20.32 ± 0.40 Ma, which is within error of ~19.83 ± 0.10 Ma adularia. The new LA-ICP-MS zircon U-Pb host rock and vein adularia 40Ar/39Ar ages suggest that early Miocene magmatism and mineralization in the Bazman area is of a similar age to that of the Saindak porphyry and Tanjeel porphyry center of the giant Reko Diq deposit. This confirms the existence of early Miocene arc magmatism and mineralization along the Iranian part of the Makran volcanic arc. Ore, alteration mineralogy, and alteration patterns indicate that the Chahnaly deposit is a typical low-sulfidation epithermal Au deposit, located in a poorly explored part of the Makran volcanic arc in Iran.

Assessing temporal and spatial alterations of flow regimes in the regulated Huai River Basin, China

The assessment of flow regime alterations is fundamental in understanding the potential impact of reservoirs and other water infrastructures on aquatic ecosystems and biota. Previously used methods to classify flow regimes have not captured temporal changes between unregulated and regulated flow regimes at individual stations. In this study, a combination of hierarchical classification and trend analysis was used to assess spatial and temporal flow regime alterations in the Huai River Basin, China. Two categories of flow regime indices were selected to characterize the impacts of reservoir and sluice regulation, including the basic flow indices for mean variation, and the cumulative variation indices for long-term alteration. The overall impact of reservoirs and sluices on flow regime included the decrease of high flow magnitudes but the increase of low flow magnitudes through time. Moreover, on average, the flow variability, and the high and low flow frequencies were reduced, while their durations were increased. Reservoirs had a greater impact on flow regimes than sluices. The flow regimes at 18 of 30 stations were altered significantly from a pre-regulation condition and were divided into three main types of alteration corresponding to operational rules of reservoirs and sluices. From a management perspective, water projects in China should address the environmental flow requirements of the rivers, particularly in terms of the hydrologic indices affected mostly by reservoirs and sluices. This study will promote the application of flow regime classification and river restoration in highly regulated basins in China. (C) 2015 Published by Elsevier B.V.

Laboratory study on engineering geological characteristics and formation mechanism of altered rocks of Henan Tianchi pumped storage power station, China

Concentrations of biotite flakes were distributed at multiple locations during the site investigation for the Tianchi Pumped Storage Power Station project in Henan Province, China. Rock mass was highly weathered on both sides of a prominent fault, and a large number of white and gray, locally yellow–brown, argillaceous agglomerations were observed. The local core at the end of the ZK44 hole presented a gray and white sandstone structure. Petrochemical tests, which included sheet identification, scanning electron microscopy, electron probe analysis, and X-ray diffraction, showed that the main alteration types were mica-rich-type altered rocks and clay-type altered rocks, which were accompanied by chlorite, epidote, actinolite, and other alteration minerals. According to the mechanical test results, the smallest antidisintegration index was 84 %, disintegration was easily accomplished, the maximum axial free expansion rate was 0.00204 %, the maximum free expansion rate in the radial direction was 0.0178 %, and maximum lateral constrained expansion rate was 0.0194 %. The swelling pressure of all the specimens did not exceed 10 kPa, and the clay-type altered rocks exhibited three large expansion parameters. Uniaxial and triaxial compression tests showed that the strength of granite, as reflected by its deformation and elastic moduli, decreased to values even lower than those of highly weathered rocks because of alteration. The poor characteristics of the altered rock presented great challenges for support or lining during the construction and operation stages. After excavation, the expanded altered rocks should be cleaned up immediately, the support or lining should be in place immediately, and water should be drained in time.

Image Segmentation for Hydrothermal Alteration Mapping Using PCA and Concentration–Area Fractal Model

Information extraction from processed remotely sensed images, in the case of missing initial spectra of pixels, can be a challenge for the users. In such situations, application of conventional methods based on spectral properties of pixels is impractical. We took advantage of the fractal theory for image segmentation of a principal component (PC) image for hydrothermal alteration mapping. The selected input images included short wave infrared bands of ASTER imagery covering the Darrehzar porphyry copper mine and surrounding areas with well-known hydrothermal alteration zones. Hydrothermal alteration like other geological processes can show spatial distribution with fractal properties. Principal component analysis was used to enhance hydrothermal alteration associated with the Darrehzar porphyry copper deposit. None of the resulting PCs were appropriate to portray clearly important alteration types in the study area. The PC1 image, which contains more than 98% of variance of the input bands, was selected for image segmentation using a digital number–area technique based on the established concentration–area fractal model. This technique was proposed based on frequency distributions and spatial correlation and variability of pixel values. The resulting hydrothermal alteration map indicates intense phyllic, weak phyllic, and propylitic as the main alteration types exposed at the surface of the Darrehzar area. In addition, the proposed technique delineated the phyllic zone in the exposed mine pit and a transition zone between inner phyllic and surrounding propylitic alteration zones. Field investigation and sampling in 23 locations including spectral measurements, XRD and thin section studies, confirmed the accuracy of the classified image by the proposed technique.

Arsenian pyrite-bearing altered volcanics dredged SE of Cheshire Seamount, western Woodlark Basin, Papua New Guinea

In many subaerial hydrothermal ore deposits arsenian pyrite is an important host for Au, however, arsenian pyrite is rare on the modern seafloor. During a recent survey for submarine hydrothermal mineralization in the western Woodlark Basin volcanic breccias containing abundant arsenian pyrite were dredged from the flanks of a volcanic seamount in a water depth of 2000 m. This area is particularly interesting because it is located at the transition from continental splitting to oceanic spreading where enhanced heat flow and deep crustal faults may fertilize mineralization. The sulfidic breccia is essentially monomictic and matrix-supported containing altered dacitic clasts. Mineralogical investigation of the breccia reveals silicification and sulfidation as the main alteration types. Quartz occurs in fragments and also constitutes the breccia matrix attesting to silicification as a significant alteration process. Pyrite is the dominant ore mineral with only minor amounts of Fe-oxyhydroxide and goethite. Bulk geochemistry shows a slight enrichment of Au (0.12 ppm) in association with elements such as As-Ag-Hg-Zn-Pb-Sb, key elements indicative of a low sulfidation environment. Three generations of pyrite are recognized on the basis of morphology. Arsenic-free, early framboidal pyrite (py1) is overgrown by arsenian colloform (py2) or massive pyrite (py3) containing up to 3.93 wt% As. Arsenic speciation in the pyrite is in the form of As1- and As3+. The presence of arsenian pyrite in hydrothermal breccias at this seamount indicates the potential for Au mineralization in the area.

Contexto geológico, estudos isotópicos (C, O e Pb) e associação metálica do depósito aurífero Tocantinzinho, domínio Tapajós, Província Tapajós-Parima

The Tocantinzinho ore deposit is located along a NW-SE-trending lineament, southwestern of Itaituba (Para, Brazil), and is the largest known gold deposit of the Tapajos Province. The host Tocantinzinho granite is essentially isotropic and dominated by syenogranites and monzogranites that have been weakly to moderately altered by hydrothermal fluids. Microclinization (earliest), chloritization, sericitization, silicification and carbonatization (latest) are the main types of alteration. Most mineralization was contemporaneous with the sericitization/silicification and is represented by sulfide- and gold-bearing veinlets which locally occur as stockwork. Pyrite, chalcopyrite, sphalerite and galena are the most common sulfides. Among the ore metals, Cu, Pb and Zn present the highest contents, but Mo, As and Bi locally show anomalous concentrations. The relationship of Au with Cu, Pb or Zn is at random and the Au/Ag ratios range from 0.05 to 0.5. The higher the sulfide contents, the higher the Au concentrations, though it occurs mainly included in pyrite. Zircon monocrystals from the Tocantinzinho granite yielded an average Pb-Pb age of 1982 ± 8 Ma and may represent an earlier event of the Creporizao magmatic arc. δ13C PDB values for calcite from the carbonatization stage fall dominantly between -3.45 and -2.29‰, being compatible with a deep crustal source that may include carbonatite reservoirs. In turn, δ18O SMOW values vary from +5.97 to +14.10‰, being indicative of magmatic derivation, although the less positive values suggest contribution from surficial waters. Unpublished fluid inclusion study reveals the presence of aquo-carbonic fluids, whose CO2 could have been dissolved in the granitic magma rather than being related to the shear zone. The available data allow the Tocantinzinho deposit to be classified as a granite-hosted, intrusion-related gold deposit.

Genetic investigation and comparison of Kartaldağ and Madendağ epithermal gold deposits in Çanakkale, NW Turkey

Two epithermal gold deposits (Kartaldağ and Madendağ) located in NW Turkey have been characterized through the detailed examinations involving geologic, mineralogical, fluid inclusion, stable isotope, whole-rock geochemistry, and geochronology data.The Kartaldağ deposit (0.01–17.65ppm Au), hosted by Eocene dacite porphyry, is associated with four main alteration types with characteristic assemblage of: i) chlorite/smectite–illite±kaolinite, ii) quartz–kaolinite, iii) quartz–alunite–pyrophyllite, iv) quartz–pyrite, the last being characterized by three distinct quartz generations comprising massive/vuggy (early), fine–medium grained, vug-lining (early), and banded, colloform, comb (late) textures. Observed sulfide minerals are pyrite, covellite, and sphalerite. Oxygen and sulfur isotope analyses, performed on quartz (δ18O(quartz): 7.93 to 8.95‰ and calculated δ18O(H2O): −7.95 to 1.49‰) and pyrite (δ34S(pyrite): −4.8‰ and calculated δ34S(H2S): −6.08 to −7.20‰) separates, suggest a meteoric water source for water in the hydrothermal fluid, and an igneous source for the sulfur dissolved in ore-related fluids. Microthermometric analyses of primary fluid inclusion assemblages performed on quartz (late quartz generation) yield temperatures (Th) dominantly in the range of 245–285°C, and generally low salinity values at 0 to 1.7wt.% NaCl eq. Based on the quartz textures and the associated base metal concentrations, along with fluid inclusion petrography, the early vug-lining quartz is considered to have been associated with the mineralization possibly through a boiling and a late mixing process at >285°C.The Madendağ deposit (0.27–20.60ppm Au), hosted by Paleozoic mica schists, is associated with two main alteration types: sericite–illite–kaolinite, and quartz–pyrite dominated by two distinct quartz generations i) early colloform, comb and banded quartz and ii) late quartz, forming the cement in hydrothermal breccia. Whereas oxygen isotope analyses of quartz (δ18O(quartz): 9.55 to 18.19‰ and calculated δ18O(H2O): −2.97 to 5.54‰) suggest varying proportions of meteoric and magmatic sources for the ore bearing fluid, sulfur isotope ratios (δ34S(pyrite): −2.2‰ and calculated δ34S(H2S): (−3.63) to (−3.75) ‰) point to an essentially magmatic source for sulfur with or without contribution from sedimentary sources. Microthermometric analysis carried out on primary fluid inclusion populations of a brecciated sample (early quartz), give a temperature (Th) range of 235–255°C and 0.0 to 0.7wt.% NaCl eq. salinity. Based on the textural relationship, base metal and high gold contents, the ore precipitation stage is associated with late stage quartz formation via a possible boiling process.The presence of alunite, pyrophyllite and kaolinite, vuggy quartz and covellite suggest a high-sulfidation type of epithermal deposit for Kartaldağ. On the other hand, Madendağ is identified as an adularia-sericite type owing to the presence of significant sericite, neutral pH clays (mostly illite, chlorite/smectite, and kaolinite), low temperature quartz textures (e.g., colloform, comb, and banded quartz), and limited sulfide minerals.Given the geographical proximity of Kartaldağ and Madendağ deposits, the similar temperature and salinity ranges obtained from their fluid inclusions, and the similar ages of igneous rocks in both deposits (Kartaldağ: 40.80±0.36 to 42.19±0.45Ma, Madendağ: 43.34±0.85Ma) the mineralizing systems in both deposits are considered to be genetically related.

زمین شناسی، دگرسانی، کانی سازی و مطالعات ژئوشیمیایی در منطقه کلاته تیمور، شمالشرق ایران

The area is located 20 km northwest of Kashmar and about 4 km of Kalateh Taimour in Khorasan Razavi province. The study area is part of Tertiary volcanic-plutonic belt north of Daruneh fault and its situation in tectonic inliers between two important active faults, Doruneh and Taknar. Volcanic rocks are mainly intermediate to acid pyroclastic type. They formed during early Tertiary. The volcanic rocks of the Kalateh Taimour area are predominantly andesitic basalt, andesite, latite, trachyte, dacite and rhyodacite and are observed as lava, tuff, lapilli tuff and agglomerate. Field evidences and study show several subvolcanic bodies including quartz hornblende biotite monzodiorite porphyry, quartz biotite monzodiorite porphyry, quartz diorite porphyry and microdiorite which are intruded sometime in mid-Tertiary. In this belt, new methods of image processing were used for enhancing the alteration zones to help near infra red and short wavelength infrared and bands example band ratios and principle component method. Propylitic, sericitic and argillic are the main alteration types. Minor silicification is found in some areas. Alteration is extent but mineralization is limited. Mineralization is mainly controlled by fault system. Several mineralized faults are being discovered. Open space filling features are abundant. In the study area, disseminate and stock work mineralization are abundant. The amount of sulfide minerals is very small. Ancient mining is present in the area. Stream sediment geochemical study shows a very broad and high level of gold anomaly. Rock geochemical study show very high levels of Au, Ag, Cu, Pb, Zn and Au value is correlative to Cu, Pb, Zn and Ag values. Due to alteration modeling, non uniformity in mineralization and low abundance of sulfide mineralization suggest study in low sulphidation Au-Cu deposit.