IntroductionPyrite is the most abundant sulfide mineral in low sulfidation ore deposits. Experimental studies have shown that low-temperature ( 200°C) from hydrothermal or metamorphic fluids (Butler and Rickard, 2000). Framboidal pyrite mostly occurs in sedimentary environments, though it could also form during metamorphism and hydrothermal alteration (Scott et al., 2009). pyrite formed tends to be enriched in various trace elements such as Au and As. For this study we have combined the geology, alteration, mineralization with recent studies of the description of the deposit from core logging and underground mapping and geochemistry in the CheshmehZard gold district and also investigated the compositional variation and textural differences between pyrite types. This study is based on the results of our alteration and mineralization mapping and detailed logging of 1937.8 m of drill core.Materials and Methods hydrothermal alteration and mineralization were examined in drill holes along several cross sections. Host-rock alteration minerals and veins were determined for 11 samples using standard X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF) techniques. Polished sections were studied by reflected light microscopy and backscattered electron images (BSE). In this study, the trace-element composition of pyrite samples from the Au-III vein system was obtained using electron microprobe analyzer (EMPA) data. All analyseswere carried out at the department of Materials Engineering and Physics of the University of Salzburg in Austria. EMPA measurements and BSE imaging were made using a JXA-8600 electron microprobe. Spot analyses of 30 pyrite grains from CheshmehZard are given in Table 1.ResultsThe study area is located in the north of Khorasan Razavi Province 45 km to the south of Neyshabour. area near CheshmehZard could become important as a site of economically significant gold mineralization. Six gold-bearing vein systems were recognized east of Arghash. estimated resources are about 2 million metric tons of potential ore with an average of 1.9 g/t Au (Samadi, 2001;Ashrafpour et al., 2012). Multiple intrusive events are recognized in the region including Precambrian to post-Oligocene-Miocene igneous rocks (Alaminia et al., 2013a). This includes the Arghash diorite pluton, upper Cretaceous granitoids (minor diorite, mainly quartz monzodiorite and granodiorite), early Eocene granite and several lamprophyre and small intrusions of quartz monzodiorite porphyries. Volcanicsinclude andesite, dacite, pillow basalt and tuffs. Sedimentary rocks are conglomerate and minor limestone. Gold veins are hosted by intermediate to silicic volcanic rocks, tuffs, granite, granodiorite, and conglomerate. Veins consist of calcite and quartz. main alteration zones mapped at the surface and underground are sericite-quartz-pyrite-calcite, withsilicified, propylitic, argillic, and carbonate zones. The mineralization associated with sericiticalteration and silicificationoccurs asveinlets and disseminated in the propylitic zone. Gangue minerals are quartz, chalcedony, calcite, adularia, illite, and kaolinite. Mineralization occurs as veinlets, breccia filling and disseminated. veinlets are comprised of pyrite, arsenopyrite, minor chalcopyrite, sphalerite, galena, magnetite and hematite. Pyrite is the main sulfide mineral in the hypogene ore. Samples were collected with the objective of studying the pyrite in the Au (III) vein systems. All samples were therefore pyrite rich. paragenesiswas determined to show four stages of mineralization based on the following microscopic observations: 1. an initial pyrite veinlet stage with associated quartz, chlorite, epidote. Pyrite is fine to medium grained, anhedral and gold-poor. 2. a second pyritic stage (polymetallic sulfide stage) contains pyrite, chalcopyrite, galena, sphalerite, quartz and chalcedony, minor adularia and arsenopyrite. 3. An As-bearing pyrite stage with sericite, chalcedony and quartz. pyrite isframboidal.. 4. Finally, a carbonate-dominated stage. pyrite is euhedral to anhedral and coarse grained. Au concentration in Stages 2 and 3 pyrite is higher than that in Stage 4 pyrite. Conclusions gangue mineral assemblages of carbonate, chlorite, quartz, and minor sericite and potassium feldspar in the ore-forming process of the CheshmehZard gold district suggest that the pH value of the hydrothermal fluids was near neutral to slightly acid (approximately 4.5 to 5.3 under 250 to 300 °C and 1 kbar conditions) and that gold would be transported mainly as Au(HS)2- (Stefansson and Seward, 2004). Three types of pyrite based on the chemical composition have been investigated: As- bearing pyrite, Ti-V - bearing pyrite and pure or barren pyrite. EMPA analyses of the pyrite in gold veins show maximum concentrations of As (3.62 wt.%), Ti (3.91 wt.%) and V (0.53 wt.%) respectively. occurrence of the gold is usually associated with arsenian pyrite and Ti-V - bearing pyrite. Veinlets of the Py1 coexisting with arseno pyrite and gold Py2 implies the substitution of sulfur by arsenic. Gold precipitated under relatively reducing conditions in framboidal pyrite. Py3 formed prior to barren pyrite (IV). ReferencesAlaminia, Z., Karimpour, M.H., Homam, S.M. and Finger, F., 2013a. magmatic record in the Arghash region, NE Iran, and tectonic implications. International Journal of Earth Sciences, 102(6):1603-1625.Ashrafpour, E., Ansdell, K.M. and Alirezaei, S., 2012. Hydrothermal fluid evolution and ore genesis in the Arghash epithermal gold prospect, northeastern Iran. Journal of Asian Earth Sciences, 51(1):30–44. Butler, I.B. and Rickard, D., 2000. Framboidal pyrite formation via the oxidation of iron (II) monosulfide by hydrogen sulphide. Geochimica et Cosmochimica Acta, 64(15): 2665–2672. Samadi, M., 2001. Exploration in Arghash Gold Prospect. Geological Survey of Iran, unpublished report, Tehran, 73 pp. (in Persian)Scott, R.J., Meffre, S., Woodhead, J., Gilbert, S.E., Berry, R.F. and Emsbo, P., 2009. Development of framboidal pyrite during diagenesis, low-grade regional metamorphism, and hydrothermal alteration. Economic Geology, 104(8):1143–1168.Stefansson, A. and Seward, T.M., 2004. Gold (I) complexing in aqueous sulphide solutions to 500 °C at 500 bar. Geochimica et Cosmochimica Acta, 68(20):4121–4143.

منطقه ارغش- قاسم آباد در شمال‌شرق ایران و در حاشیه زون ساختاری سبزوار قرار دارد. رخنمونهای ترشیری شامل گرانیت و کوارتز مونزودیوریت پورفیری همراه با سنگهای آتشفشانی از نوع داسیت و آندزیت هستند. در منطقه مورد مطالعه، دایک‌هایی از نوع کوارتز گابرو و کوارتز مونزودیوریت، سنگهای قدیمی تر را مورد نفوذ قرار داده اند. گرانیت‌ها و سنگهای آتشفشانی، میزبان رگه های کوارتز-‌کلسیت طلا و آنتیموان دار هستند. رگه های کانی سازی عمدتا در اطراف دایک‌ها و در نیمه جنوبی منطقه دیده می شوند. مطالعات ژئوشیمیایی حاصل از این پژوهش نشان می دهد که گرانیت‌ها ماهیت کالک‌آلکالن پتاسیم بالا داشته، و از نوع گرانیتوئیدهای انتقالی بین دو نوع A و I هستند. سنگهای آتشفشانی نیز با ترکیب آداکیتی، سرشار از استرانسیم و باریم می‌باشند. دایک‌های منطقه مورد مطالعه، ویژگیهای سنگهای لامپروفیری را نشان می دهند. سن سنجی اورانیم- سرب بر روی زیرکن در گرانیت، سن 2/2 ± 4/55 میلیون سال (ائوسن زیرین) را نشان می دهد. نسبتهای 87Sr/86Sr و eNd اولیه در گرانیت‌ها به‌ترتیب 704142/0 و 84/5+ می-باشند. داده های نسبتهای ایزوتوپی 87Sr/86Sr اولیه، وجود ماگمایی با منشأ گوشته تهی‌شده را تأیید می کند. سن به‌دست آمده نشان می دهد کانی سازی طلا- آنتیموان از ائوسن زیرین جوانتر است. براساس شواهد صحرایی، ارتباط کانی سازی با دایک‌های لامپروفیری، بیش از ارتباط آن با سنگهای آداکیتی است.

منطقه اکتشافی طلای ارغش در شمال‌شرق پهنه ایران مرکزی قرار دارد. این منطقه در پهنه ساختاری سبزوار در شمال گسل درونه واقع است. رخنمون‌های سنگی شامل سنگ‌های آتشفشانی با سرشت داسیت و آندزیت، سنگ‌های درونی با طبیعت دیوریت، کوارتزدیوریت، کوارتز مونزودیوریت، گرانودیوریت و گرانیت و سنگ‌های رسوبی با ترکیب آهک، ماسه‌سنگ و کنگلومرا هستند. مطالعه سنگ‌های نفوذی دیوریت، کوارتزدیوریت، کوارتزمونزودیوریت و گرانودیوریت گویای تعلق این مجموعه به سری مگنتیت (نوع I)، پتاسیم متوسط و متاآلومین است. این سنگ‌ها با کانی‌زایی ضعیف آهن در منطقه همراه هستند. عناصر TiO2، P2O5، Nb، La و Zr در توده‌ها دارای مقادیر پایین و نسبت‌های ایزوتوپی 87Sr/86Sr اولیه و eNd اولیه در آن‌ها به‌ترتیب 703755/0 و 74/4+ است. سن این توده‌ها بر اساس سن‌سنجی اورانیوم- سرب زیرکن 9/0± 8/92 میلیون سال (کرتاسه بالایی) است. داده‌های ترکیب زمین‌شیمیایی و نسبت‌های ایزوتوپی 87Sr/86Sr اولیه، وجود ماگمایی با منشأ گوشته تهی‌شده و مرتبط با پهنه فرورانش اقیانوس قدیمه سبزوار را تأیید می‌کنند.

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.