The application of geochemical pattern recognition to regional prospecting: A case study of the Sanandaj–Sirjan metallogenic zone,Iran     

Seyed Ahmad Meshkani  Behzad Mehrabi  Abdolmajid Yaghubpur  Younes Fadakar Alghalandis 《Journal of Geochemical Exploration》2011

In regional exploration programs, the distribution of elements in known mineral deposits can be used as a guide for the classification of deposits, search for new prospects and modeling ore deposit patterns. The Sanandaj–Sirjan Zone (SSZ) is a major metallogenic zone in Iran, containing lead and zinc, iron, gold, copper deposits. In the central part of the SSZ, lead and zinc mineralization is widespread and hitherto exploration has been based on geological criteria. In this study, we used clustering techniques applied to element distribution for classification lead and zinc deposits in the central part of the SSZ. The hierarchical clustering technique was used to characterize the elemental pattern. Elements associated with lead and zinc deposits were separated into four clusters, encompassing both ore elements and their host rock-forming elements. It is shown that lead and zinc deposits in the central SSZ belong to two genetic groups: a MVT type hosted by limestone and dolomites and a SEDEX type hosted by shale, volcanic rocks and sandstone. The results of elemental clustering were used for pattern recognition by the K-means method and the respective deposits were classified into four distinct categories. K-means clustering also reveals that the elemental associations and spatial distribution of the lead and zinc deposits exhibit zoning in the central part of the SSZ. The ratios of ore-forming elements (Sb, Cd, and Zn) vs. (Pb and Ag) show zoning along an E–W trend, while host rock-forming elements (Mn, Ca, and Mg) vs. (Ba and Sr) show a zoning along a SE–NW trend. Large and medium deposits occur mainly in the center of the studied area, which justify further exploration around occurrences and abandoned mines in this area. The application of a pattern recognition method based on geochemical data from known mineralization in the central SSZ, and the classification derived from it, uncover elemental zoning, identify key elemental associations for further geochemical exploration and the potential to discover possible target areas for large to medium size ore deposits. This methodology can be applied in a similar way to search for new ore deposits in a wide range of known metallogenic zones.  相似文献   

Seasonal Changes in Mayfly Communities and Abundance in Relation to Water Physicochemistry in Two Rivers at Different Elevations in Northern Peninsular Malaysia     

Suhaila Abdul Hamid  Mohd Ravi Che Salmah  Hamady Dieng  Abu Hassan Ahmad  Tomomitsu Satho  Fumio Miake 《湿地科学》2011,9(3):240-250

A field study was performed at rivers in Gunung Jerai forest reserve(Kedah,Malaysia) to assess seasonal changes in mayfly community structure and abundance in relation to altitude and water physicochemistry.Rivers at lower(Batu Hampar River) and higher(Teroi River) elevations were visited through dry and wet seasons in September 2007 to August 2008.Monthly visits were made to 20 sites on each river,and water and aquatic insects were sampled using D-pond aquatic nets.Water was warmer,more acid,and more turbid in Teroi River during wet season.Ammonia was the only nutrient exhibiting significant seasonal variations(greater during wet season).Chemical oxygen demand content was higher in Teroi River where biochemical oxygen demand content was low during wet season.Species richness was higher in Batu Hampar River,but displayed seasonal variations only in Teroi River.Among the eight families encountered,Baetidae was the commonest.Baetid abundance was usually high during wet season,and those belonging to the dominant genus(Baetis) were more abundant in Teroi River.Heptageniidae was the second commonest family;its predominant genus,Thalerospyrus was more abundant in Teroi River during dry season.Caenidae,Leptophlebiidae and Oligoneuriidae were only found in Batu Hampar River where their abundances peaked during dry season,i.e.,Habrophlebiodes sp.and Isonychia sp.Ephemerellidae and Teloganodidae occurred only in Teroi River,with the first found only during dry season.Mayflies were recorded under very distinct physicochemical conditions,illustrating their potential usefulness for assessing water quality.Caenids,leptophlebids,oligoneurids ephemerellids and teloganodids seem to be particularly sensitive to temperature,acidity,turbidity,chemical oxygen demand and biochemical oxygen demand,parameters that varied with river altitude.  相似文献   

New chelating resin for preconcentration and determination of molybdenum by inductive couple plasma atomic emission spectroscopy     

H. Sid Kalal Ph.D.  H. Ahmad Panahi Ph.D.  N. Framarzi  E. Moniri Ph.D.  A. Naeemy  H. Hoveidi Ph.D.  A. Abhari 《International Journal of Environmental Science and Technology》2011,8(3):501-512

A chelating resin is prepared by condensation polymerization of aniline with formaldehyde and characterized by Fourier transform infrared spectrometer, elemental analysis and thermogravimetric analysis and studied for the preconcentration and determination of trace Molybdate ion from environmental water sample using inductive couple plasma atomic emission spectroscopy. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 3.1 mg/g. The chelating sorbent can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. The best desorption of the metal ions from resin was obtained by 0.5 mol/L nitric acid as eluting agent. The profile of molybdenum uptake on this sorbent reflects good accessibility of the chelating sites in the aniline-formaldehyde. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Molybdate ion modified resin were analyzed by five isotherm models such as Langmuir, Freundlich and Temkin. Langmuir isotherm parameters obtained from the four Langmuir linear equations by using linear method. Based on the Langmuir isotherm analysis, the monolayer adsorption capacity was determined to be 4.03 mg/g at 20 °C. The method was applied for molybdenum ions determination from river water sample.  相似文献   

State of stress in the northern Tabas block, east-central Iran, as inferred from focal mechanisms of the 1978 Tabas earthquake sequence     

G. Behzad Zamani 《Central European Journal of Geosciences》2011,3(1):77-89

In this paper, the state of stress in the northern Tabas block in east-central Iran is analyzed based on the systematic inversion of aftershock focal mechanisms from the 1978.09.16 Tabas earthquake, to characterise the stress regime that controls most earthquakes in this area. Here, stress inversions of double-couple focal mechanisms of earthquakes recorded during the 30 days following the main shock have been carried out. The calculated average stress regime indicates dominant major 226° to 237° trending compression for the Tabas region. The dominating regime in east-central Iran is thrusting with a minimum stress axis, σ ₃, close to vertical. The reconstruction of the main seismotectonic stress in east-central Iran with a NE-SW compression is consistent with independent information of the active plate convergence related to Arabia-Eurasia convergence. Most earthquakes in the mentioned area occur near or around concealed Quaternary thrust faults with their activity being controlled by the NE-SW compression. Where ?, the ratio of principal stress differences, is 0.5, a small difference between σ ₂; σ ₃ and σ ₁ and small amounts of deviatoric stress is indicated. Therefore, for small deviatoric horizontal σ ₁ it is not possible to increase and reactivate small sections of basement thrust faults and create secondary basement aftershocks. Reconstructed stress regimes in this study for sedimentary cover (237) and basement (226) of Tabas are similar. Therefore, it seems that the basement and cover were coupled together, possibly along the 2–4 km of upper Precambrian low-grade metamorphic rocks. Then these segments of the fold-and-thrust belt were involved in similar seismic activity under a similar stress regime.  相似文献   

Region of motion in the Sitnikov four-body problem when the fourth mass is finite     

L. P. Pandey  I. Ahmad 《Astrophysics and Space Science》2013,348(2):377-383

This article deals with the region of motion in the Sitnikov four-body problem where three bodies (called primaries) of equal masses fixed at the vertices of an equilateral triangle. Fourth mass which is finite confined to moves only along a line perpendicular to the instantaneous plane of the motions of the primaries. Contrary to the Sitnikov problem with one massless body the primaries are moving in non-Keplerian orbits about their centre of mass. It is investigated that for very small range of energy h the motion is possible only in small region of phase space. Condition of bounded motions has been derived. We have explored the structure of phase space with the help of properly chosen surfaces of section. Poincarè surfaces of section for the energy range ?0.480≤h≤?0.345 have been computed. We have chosen the plane (q ₁,p ₁) as surface of section, with q ₁ is the distance of a primary from the centre of mass. We plot the respective points when the fourth body crosses the plane q ₂=0. For low energy the central fixed point is stable but for higher value of energy splits in to an unstable and two stable fixed points. The central unstable fixed point once again splits for higher energy into a stable and three unstable fixed points. It is found that at h=?0.345 the whole phase space is filled with chaotic orbits.  相似文献   

Timescales of partial melting in the Himalayan middle crust: insight from the Leo Pargil dome, northwest India   总被引：5，自引：0，他引：5  

Graham W. Lederer  John M. Cottle  Micah J. Jessup  Jackie M. Langille  Talat Ahmad 《Contributions to Mineralogy and Petrology》2013,166(5):1415-1441

The Leo Pargil dome (LPD) in northwest India exposes an interconnected network of pre-, syn-, and post-kinematic leucogranite dikes and sills that pervasively intrude amphibolite-facies metapelites of the mid-crustal Greater Himalayan sequence. Leucogranite bodies range from thin (5-cm-wide) locally derived sills to thick (2-m-wide) crosscutting dikes extending at least 100 m. Three-dimensional exposures elucidate crosscutting relations between different phases of melt injection and crystallization. Combined laser ablation inductively coupled plasma mass spectrometry U–Th/Pb geochronology and trace element analysis on well-characterized monazite grains from nineteen representative leucogranites yields a large, internally consistent data set of approximately 700 U–Th/Pb and 400 trace element analyses. Grain-scale variations in age correlate with trace element distributions and indicate semi-continuous crystallization of monazite from 30 to 18 Ma. The youngest U–Th/Pb ages in a given sample are consistent with the outcrop-scale crosscutting relations, whereas older ages within individual samples record inheritance from partially crystallized melt and source metapelites. U–Th/Pb isotopic and trace element data are incorporated into a model of melting within the LPD that involves (1) steady-state equilibrium batch melting of compositionally homogeneous metapelitic sources; (2) pulses of increased melt mobility lasting 1–2 m.y. resulting in segregation of melt from its source and amalgamation into mixed magmas; and (3) rapid emplacement and final crystallization of leucogranite bodies. Melt systems in the LPD evolved from locally derived, in situ melt in migmatitic source rocks into a vast network of dikes and sills in the overlying non-migmatitic host rocks.  相似文献   

The origin of tin deposits in the Mount Wells region,Pine Creek Geosyncline,Northern Territory     

M. Ahmad 《Australian Journal of Earth Sciences》2013,60(5):427-443

Tabular steeply dipping cassiterite‐bearing lodes in the Mount Wells region are hosted by lower greenschist fades metasediment of the Pine Creek Geosyncline within the contact aureole of late orogenic granitoids. The latter are predominantly I‐type, but S‐type phases are developed near the sediment‐granitoid contact.

Quartz, cassiterite, pyrite, arsenopyrite, chalcopyrite and pyrrhotite are the main minerals. Two types of lodes are present: (i) Sn‐quartz lodes containing 5–10 vol% sulphide minerals; and (ii) Sn‐sulphide lodes containing ～ 70 vol% sulphide minerals. At the surface, the former appear as normal quartz veins and the latter as hematite‐quartz breccia resulting from the collapse of original sulphide‐rich lodes as a consequence of volume reduction due to oxidation and leaching.

Two stages of quartz veining are recognized in both types of lodes. Cassiterite is present in stage I while stage II is composed of barren quartz with minor pyrite. Late stage III carbonate veinlets are present in Sn‐sulphide lodes. The lode‐wallrock contact is sharp with weak alteration effects confined to the fringe of the lodes. The alteration minerals include sericite, quartz, tourmaline, chlorite, pyrite and minor K‐feldspar.

Four types of fluid inclusions are present in vein quartz and cassiterite: Type A (CO₂ ± H₂O ± CH₄); Type B (H₂O+～ 20% vapour); Type C (H₂O+ < 15% vapour) and Type D (H₂O+ < 15% vapour + NaCl). Early ‘primary’ inclusions represented by Types A and B are present in stage I only and have a well‐defined temperature mode at ～300°C and a salinity range of 1–20 wt% eq NaCl. Types C and D inclusions are ‘secondary’ in stage I and primary in stage II and have a temperature mode at 120–160°C and salinities from about 1 to more than 26 wt% eq NaCl. Variable H₂O‐CO₂ ratios of Type A inclusions and homogenization in CO₂ or H₂O phase at near identical temperature indicate entrapment at the H₂O‐CO₂ solvus and define a pressure of ～ 100 MPa. The melting sequence of frozen inclusions suggests that the ore fluids were mainly H₂O‐CO₂‐CH₄‐Na‐Ca‐Cl brines. This is also confirmed by Raman Laser Spectrometry.

Oxygen and sulphur isotope data are consistent with a magmatic origin of the ore fluids. The δD values are up to 20%0 higher than those expected for magmatic fluids and probably resulted from interaction of the latter with the carbonaceous strata. This interpretation is supported by δ¹³C data on the fluid inclusion CO₂.

Fluid inclusions, stable isotope and mineralogical data are used to approximate the physico‐chemical parameters of the ore fluids which are as follows: T 300°C, m Cl～2, fO₂ ～ 10^‐35, mSS ～ 0.01, Sn ～ 1 ppm, Cu ～ 1 ppm and pH ～ 5.5.

It is suggested that fluids of granitic parentage interacted with the enclosing sediment and picked up CO₂, CH₄ and possibly Ca. The granitic phases became reduced due to this interaction and developed S‐type characteristics. Tin was probably partitioned into the CH₄‐bearing reduced fluids. At some stage the fluid overpressure exceeded the lithostatic lode enforcing failure of the carapace and the intruded rocks by hydraulic fracturing causing CH₄ and CO₂ loss resulting in the precipitation of the ore minerals.  相似文献   

A new evaluation of seismic hazard for the northwestern part of Saudi Arabia     

Al-Arifi  Nassir S.  Fat-Helbary  R. E.  Khalil  Ahmad R.  Lashin  Aref A. 《Natural Hazards》2013,69(3):1435-1457

Natural Hazards - A new evaluation of seismic hazard in the northwestern part of Saudi Arabia area has been carried out, for the minimization and mitigation of earthquake losses. The study area...  相似文献   

Effects of natural and calcined poultry waste on Cd, Pb and As mobility in contaminated soil   总被引：1，自引：0，他引：1  

Jung Eun Lim  Mahtab Ahmad  Adel R. A. Usman  Sang Soo Lee  Weon-Tai Jeon  Sang-Eun Oh  Jae E. Yang  Yong Sik Ok 《Environmental Earth Sciences》2013,69(1):11-20

The reuse of waste materials as soil additives could be a welcome development in soil remediation. The mobility of Cd, Pb and As in a contaminated soil was investigated using natural and calcined poultry wastes (eggshell and chicken bone), CaCO₃ and CaO at different application rates (0, 1, 3 and 5 %). The chemical composition accompanied with mineralogical composition indicated that CaCO₃ and CaO were the major components in natural and calcined eggshells, respectively, while hydroxyapatite (HAP) dominated the natural and calcined chicken bones. The results showed that soil pH tended to increase in response to increasing application rates of all soil additives. The effectiveness of the additives in reducing Cd, Pb and As mobility was assessed by means of chemical extractions with 0.1 N HCl for Cd and Pb or 1 N HCl for As, according to Korean Standard Test (KST) method. Both calcined eggshell and chicken bone were equally effective with CaO or CaCO₃ in reducing the concentration of 0.1 N HCl-extractable Cd from 6.17 mg kg^?1 to below warning level of 1.5 mg kg^?1, especially at the highest application rate. The application of calcined eggshell, CaO and CaCO₃ also decreased the concentration of 0.1 N HCl-extractable Pb from 1,012 mg kg^?1 to below warning level of 100 mg kg^?1. The Pb concentration decreased significantly with an increasing application rate of chicken bone, but remained above warning level even at the highest application rate. On the contrary, natural and calcined chicken bones led to a significant increase in the mobility of As when compared with the control soil. These findings illustrate that calcined eggshell in particular is equally effective as pure chemical additives in stabilizing Cd and Pb in a contaminated agricultural soil. The presence of As in metal-contaminated soils should be taken into consideration when applying phosphate-containing materials as soil additives, because phosphate can compete with arsenate on adsorption sites and result in As mobilization.  相似文献   

The geoaccumulation index and enrichment factor of mercury in mangrove sediment of Port Klang, Selangor, Malaysia   总被引：3，自引：0，他引：3  

Hazzeman Haris  Ahmad Zaharin Aris 《Arabian Journal of Geosciences》2013,6(11):4119-4128

Mangrove areas are important to the ecosystem. One of its crucial functions is as a sink of pollutants, especially metal ions. However, the accumulation of metals in mangrove sediment can generate negative impacts on plant growth, microbial activity, and soil fertility. Apart from that, the severity of the impact is highly influenced by the type of metal found in the sediment and the quality of sediment itself. One of the metals that have adverse effects on the environment is mercury. The objectives of this study are to determine the concentration and distribution of mercury and to assess the enrichment of mercury in Port Klang mangrove sediment by using geoaccumulation index and enrichment factor. Sediment samples were collected from 30 sampling points that cover Langat River and Klang River estuaries, Lumut Straits, Pulau Klang, and Pulau Indah. During sampling, water parameters such as pH, salinity, electrical conductivity, and total dissolved solids were measured in situ, whereas the total mercury in sediment samples was determined at the laboratory using inductively coupled plasma mass spectrometry. In this study, mercury was found to be concentrated along Lumut Strait especially in the mixing zone near the confluence of Langat River and at the jetty to Pulau Ketam. The geoaccumulation index and enrichment factor (calculated using logarithmized data of the reference element) found that three stations were enriched with mercury. In addition, geoaccumulation index was also observed to be more objective compared to enrichment factor whose results were influenced by the concentration of reference element used.  相似文献