جستجوی مقالات مرتبط با کلیدواژه « داده های زمین شیمیایی » در نشریات گروه « زمین شناسی »

Hanar intrusion located in 155 km South of Birjand in the east of Lut block and compositionally consist of tonalite, granodiorite, quartz-diorite and diorite that intruded as stock and dikes in volcanic sequence (basic to intermediate) outcropped in this area. Hanar granitoid rocks are metaluminous and show I-type granitoids affinity. In addition, they are belong to calk-alkaline series and reveal the active continental margin geochemical evidences. According to relation of studying intrusion to I type granitoids with oxide (magnesian) state, they have no potential to produce Sn and W mineralization. Also, Low Sr/Y and V/Sc ratios as well as the situation of the studying samples in barren domain of the fertile-barren discrimination diagrams show that Hanar granitoids have no potential for Cu porphyry mineralization. In other hand, Low degree of the magmatic evolution as well as location of the studying samples in different Fe-mineralization potential evaluation diagrams indicate that Hanar granitoids (Diorite unit) has high potential for formation of iron deposits that this case is supporting by occurrence of  Fe-mineralization (as vein-Iron deposit) in association with this intrusion.

The study of petrological findings and geochemical data of mafic and ultramafic rocks and related petrographic units in the ophiolites can be an introduction to environmental geology studies, agriculture and natural resources. Regarding the urban and rural areas of Nain to Ashin in the vicinity of ophiolitic zone (Central Iran), geochemical investigations of mafic and ultramafic rocks of these ophiolites have very important applications in the field of environmental geology of these areas. Therefore, available geochemical data of basic rocks (pillow lavas and basalts), metabasic rocks (amphibolites) and metamorphosed and altered peridotites are considered based on environmental factors. For examples, in the peridotites which are one of the most abundant rock units in these ophiolites, the enrichment factor (Ef) for Ni is extremely high, for Cr is very high, and for Co is high. In addition, the geo-accumulation index or Igeo for Ni (~4) and Ni (>5) in peridotites is heavily to extremely high. therefore, high Ef and Igeo factors of the studied heavy metals (e.g., chrome, nickel, cobalt, arsenic, vanadium) and asbestose minerals (hornblende, tremolite, talc and chrysotile) in the mafic and ultramafic rocks of Ophiolites can be known as some dangerous environmental pollutants. Thus, investigatation of the volume of such elements penetrated into the surface and underground waters and soils in the villages and cities at the foot of these ophiolites could be a theme for ongoing studies in environmental geology of these areas.

IntroductionUrumieh-Dokhtar Magmatic Arc (UDMA) is a good prospective area for Cu, Cu-Mo and Cu-Au deposits (Fig. 1A and B). The Zafarghand district is located in the central part of the UDMA and the northeastern Isfahan. The present study concerns geological observations, alteration investigations, geochemical data and fluid inclusion studies. The purpose of the research is to identify geochemical anomalies and source of metals in this area. Geochemical anomalies for mineralizing elements and element associations were identified by using statistical analysis methods. Additionally, these results together suggest a site for exploration drilling in this study area.
Materials and methodsWe collected 186 samples (rock) along multi-cross sections oriented perpendicular to the strike of the South -Ardestan fault (Fig. 2).Trace element concentrations were determined by the ICP-MS technique in Amdel laboratory (Australia). Thin sections and doubly polished sections (100–200 µm thick) from quartz veins were prepared from samples collected from the Zafarghand district in the University of Isfahan. Heating and freezing experiments on fluid inclusions were performed as defined (by Goldstein and Reynolds (1994) on a Linkam THM600 stage.
ResultsIgneous rocks in the Zafarghand area are dominated by the Eocene and post Eocene acidic-intermediate rocks that include dacite, rhyodacite and andesite associated with diorite, quartz diorite and microdiorite intrusions. The present investigations indicate that all rocks of the Zafarghand district exhibit a variety of alterations. Hydrothermal alterations include phyllic, potassic, silicification, and argillic with widespread propylitic. The mineralization consists of malachite, azurite, hematite, and goethite, rare amounts of magnetite, pyrite, and chalcopyrite. Numerical traditional statistical analysis techniques have been applied to interpret the geochemical data of the study area. These methods are aimed at producing maps resulting from the detecting of anomaly or threshold values from the background (Aitchison, 1986; Sun et al., 2009). Anomalies of Cu, Mo, Au, Ag, Pb, Zn and Sb were determined by Mean 2 standard deviation (Cheng, 2007; Zuo et al., 2009; Chen et al., 2016). Geochemical maps for these elements in rocks and soils (Fig. 4) show significant contrasts in haloes concentrations within the diorite and dacite rocks in the southeast of the study area. The addition of concentrations in rocks is suggested indicating that a district-scale geochemical present is confined to either base metals or precious metals. The obtained fluid inclusion results are compiled in Table 3. Primary fluid inclusions in quartz mostly consist of two-phases and rarely three phases. Homogenization temperatures (Th) in quartz samples represent wide variations from 123° to 550°C. They were classified according to the mode of homogenization into two immiscible types (Fig. 8): These are early inclusions stage with a high Th (between 328° and 550°C) and late stage inclusions with a low Th (between 123° and 390°C). The salinity measured using the equation of Bodnar (1993) for fluid inclusions varies from 1.15 to 43 eqv.wt% NaCl. It was divided into two groups including high salinity (32 to 43 eqv.wt% NaCl) and low salinity (1.15 to 5.16 eqv.wt% NaCl).
DiscussionThe predictive results obtained by field observations, geochemical and micro thermometric studies are in good agreement with the known deposits. Geochemical anomalies are associated with phyllic and rare silicified altered rocks. The host rocks of anomalies are mainly dacite and diorite, respectively with an Eocene and younger age. District-scale geochemical patterns of several elements (Cu, Mo, Au, Pb, Ag, As, and Sb) in the surface coincide with the southeastern area and can be used to explore for epithermal and/or porphyry-type deposits. Anomalies of Cu and Mo are suitable for targeting Cu-Mo mineralization. Weak anomalies associated with Au concentration should also be combined with other exploration methods to identify mineralization in the Zafarghand district.
Quartz veins are classified as V1 and V2 (Fig. 3G). Based on the properties of quartz hydrothermal fluids in the Zafarghand district, they are interpreted to have evolved in two-types of fluid fields (Fig. 7):- Stage 1 fluid inclusion: This inclusion included 32 to 43 wt percent NaCl eqv (high salinity) and homogenizing between 328° and 550°C. Primary quartz in stage 1 veins (V1) is poor inclusion and associated with sulfide minerals. It can be represented by fluids trapped during aporphyry- system episode.
- Stage 2 fluid inclusion. This inclusion typically contains

Study of source rock materials in Jajarm bauxite deposit is the main subject of this study to show its origin. From bottom to top, this deposit consists of lower argillaceous layer, argillaceous bauxite, hard bauxite and upper kaolinite units. Correlation coefficients and scatter diagrams of immobile elements in these four layers, demonstrate an early homogenous origin at the beginning of the bauxite formation. Accordingly, source materials were separated slowly due to the different conditions dominated in different parts of the deposit. Difference in drainage conditions and leaching of some elements from upper part and their re-deposition in lower parts of the deposit are the main reasons for hard bauxite separation from argillaceous one. Formation of the lower argillaceous layer, located between argillaceous bauxite and carbonate footwall is due to the direct contact of the argillaceous bauxite and carbonate footwall and also difference in drainage rate in contact area of the two layers. Geochemical evidence also depicts that upper kaolinite formation is the result of the silica leaching from upper horizons and its re-deposition in hard bauxites. Compositional comparison of studied samples with chondrite and upper continental crust demonstrates the effect of both of the basic and sedimentary rocks in evolution of the Jajarm bauxite. Formation of this deposit can be considered as a result of the alteration of the primitive laterite in an area close to the current location of the deposit. During alteration and transportation bauxite is deposited on the karstic topography and then some continental sediment was added to it.