شناسایی و مقایسه معیارهای اکتشافی کانسارهای طلای ساری‌ گونی، مس- طلای دالی و طلای زرشوران واقع در کوه‌ زاد زاگرس

ایالت متالوژنی زاگرس دارای کانسارهای مهمی نظیر طلای ساری‌گونی، مس- طلا دالی و طلای زرشوران می‌باشد. در پژوهش پیش‌رو جهت شناسایی معیارهای اکتشافی این سه کانسار، از نقشه های زمین شناس، مطالعات دور‌سنجی، ژئوشیمیایی، ژئوفیزیکی، کانی شناسی، سنگ شناسی، سیالات درگیر و سن سنجی استفاده شده است. کانی ‌سازی در ساری گونی از نوع اپی ترمال سولفید پایین می‌باشد که حدود 11 میلیون سال پیش (میوسن پایینی)  در ارتباط با ماگمای آلکالن و سنگ‌های برشی دگرسان شده داسیت پورفیری شکل گرفته ‌است. کانی سازی در کانسار دالی از نوع مس- طلا پورفیری  با سنگ میزبان دیوریتی بوده، که حدود 21 میلیون سال پیش (میوسن پسین) در رابطه با یک ماگمای کالک آلکالن شکل گرفت. کانی سازی در زرشوران، از نوع کارلین با سنگ میزبان کربناته می‌باشد، که حدود 14 میلیون سال پیش (میوسن میانی)  در ارتباط با یک ماگمای آلکالن تشکیل شده ‌است. کانی سازی در کانسارهای ساری گونی و زرشوران به رغم سنگ میزبان متفاوت، دارای معیارهای اکتشافی مشابهی بوده که از مهم‌ترین آن‌ها می‌توان به ماگماتیسم آلکالن میوسن، شکل گیری کانی سازی در اعماق بیش از 300 متر، ساختارهای با روند شمال‌- شرق، پاراژنز عناصر طلا، آرسنیک، آنتیموان، اکسید های آهن نوع هماتیتی و جاروسیتی، بافت خلل و فرج دار، برشی و  دگرسانی‌های سیلیسی و فیلیک میزبان کانی سازی اشاره کرد. از جمله معیارهای اکتشاف دالی نیز می توان به ماگماتیسم دیوریتی کالک آلکالن میوسن، شکل‌گیری کانی‌سازی در اعماق بیش از 500 متر، دگرسانی پتاسیک و سیلیسی میزبان کانی سازی، حضور کانی اسپکیولاریت،  ساختارهای با روند شمال شرق و آنومالی بالای مغناطیسی در رابطه با دگرسانی پتاسیک اشاره نمود.

identifying and comparing the exploration criteria at sari gunay gold, dalli copper-gold and zarshuran gold deposits in zagros orogen

there are important deposits such as sari gunay epithermal gold, dalli porphyry copper-gold, and zarshuran carlin deposits with a few common exploration features in the zagros metallogenic province of iran. this study used geological maps, remote sensing, geochemical, geophysical, mineralogical, petrographic, fluid inclusion and age dating information to characterize and identify exploration criteria of these deposits.  mineralization at sari gunay gold deposit is epithermal, which was formed in association with an alkaline magma and brecciated, altered dacite porphyry about 11 ma.  mineralization at zatshuran is cralin with black shale and carbonate sedimentary hosts, formed indirectly in association with a deep alkaline magma about 14 ma. mineralization at dalli deposit is copper-gold porphyry with diorite host, formed in association with a chalk alkaline magma about 21 ma. despite different host rocks, mineralization at zarhuran and sari gunay gold deposits reveals some similarities. among the common exploration criteria in the two deposits are oligo-miocene alkaline magma, mineralization depth of more than 300 meters, northeast trending structures, gold, arsenic and antimony geochemical association, presence of iron oxides such as jarosite and hematite, vuggy breccia textures, and silica and phyllic alteration hosting gold minerlization. the most important exploration criteria at the dalli deposit, however, are miocene chalk alkaline magmatism, depth of mineralization of more than 500 meters, strong potassic and phyllic alterations, presence of specularite mineral, northeast trending structures and strong high magnetic anomalies, associated with potassic alteration. introductionzagros orogenic belt and its geological subdivisions such as urumieh-dokhtar magmatic arc (udma) and sanandaj-sirjan zone (ssz), as part of alpine-himalayan belt and product of neogene closure of neo-tethys ocean, host several large porphyry copper (mo and au) and epithermal gold deposits in iran. sari gunay low sulfidation epithermal, zarshuran sediment-hosted carlin type and dalli porphyry (cu-au) deposits are three major deposits in this belt. several conceptual studies have been carried out on individual porphyry copper and epithermal gold deposits of this belt (e.g., talesh-hosseini et al., 2020; ayati et al., 2012; richards et al., 2006; hezarkhani williams-joins, 1998; mehrabi et al., 1999). nevertheless, limited studies have been conducted on the application of conceptual modelling in exploration (daeijavad et al., 2020), and comparison of porphyry copper-gold and epithermal gold mineralizations. therefore, the main objective of this research is to use earlier conceptual and description models of these deposits and, combining them with the results of this tudy, to identify various criteria for exploration across the two mentioned geological subdivisions of zagros belt. material and methodsthis study used geodynamic model of zagros belt, detailed geological maps, remote sensing data, mineralogical and petrographic studies by electron microprobe and normal microscope, icp geochemical analyses of more than 3500 surface soil samples, drill core data, 40ar/39ar age dating and fluid inclusion analyses at these deposits to characterize the controls on gold mineralization and to define exploration criteria for further exploration at sari gunay, zarshuran, and dalli, and other ones. resultssari gunay epithermal gold deposit is located in northwest of the ssz and is associated with an alkaline magma. geochemical analysis of surface and drill core samples show that gold mineralization at this deposit is associated with as, sb, hg, tl, and ag, with outer zones enriched in pb, zn, and cu. mineralization is hosted by strongly silicified subvolcanic fragmental rocks and diatreme breccias and dacite porphyritic rocks showing strong phyllic and argillic hydrothermal alterations, identified by remotely sensed image processing data. iron oxide, orpiment, realgar and stibnite minerals are closely associated with gold mineralization in the altered fragmental host rocks of dacite-lithic tuff and brecciated dacite porphyry. gold occurred as angstrom-size or solid solutions within arsenian pyrite rims over previously formed barren brassy pyrite. rare amounts of native gold noted within the late quartz, brassy pyrite, and galena veins. ar/ar and k/ar age dating and whole rock geochemical analyses showed that mineralization at sari gunay occurred at about 11 ma (oilgo-miocene).zarshuran is located in the north takab geothermal basin in northwest iran. this deposit is geologically located at the contact of the ssz and the udma. the oldest rocks are iman khan schists, followed by chaldagh limestone, zarshuran black shale, and qaradash shale. a miocene brecciated and altered dacite porphyry and locally dacite lithic tuff intruded the zarshuran black shale and chaldagh limestone. mineralization associated with silicification mostly occurred in the zarshuran black shales and chaldagh limestone and extended in a northwest direction. ar/ar and k/ar age dating revealed that mineralization at zarshuran occurred at about 14 ma and was about the time of miocene volcanic activities (13.7 ± 2.9 ma). in chaldagh limestone, gold mineralization is mostly concentrated in quartz veins. quartz veins in chaldagh limestone include barite, pyrite, arsenian pyrite, sphalerite, and iron oxides. mineralized quartz veins and jasperoid lenses in the zarshuran black shale contain arsenic-antimony sulfides, pyrite, gold-bearing arsenian pyrite, and base metal sulfides such as galena and sphalerite. mineralization showed elements association of au, as, sb, and pb.dalli is a newly discovered porphyry cu-au deposit, which is located in the western margin of udma, near the contact the ssz. discovery of dalli was initially based on alteration mapping by satellite imagery data, and then by using surface soil and rock geochemical studies, geological mapping, and magnetic surveys, which delineated two porphyry centers as targets for detailed geochemical prospecting. these porphyry centers (south hill and north hill), crop out within a northeast trending corridor of altered oligo-miocene dioritic plutonic rocks intruded into volcanic rocks. dalli is a gold-rich porphyry cu deposit in iran, with proven reserve of 5 million tons of ore containing 0.65 g/t au and 0.5% cu. mineralization is hosted by altered porphyritic amphibole-bearing diorite and occurs in quartz-hematite-magnetite stock works and veins. hypogene mineralization is characterized by chalcopyrite, pyrite, bornite, magnetite, and native gold. mineralization showed a strong element association of cu, au, and fe.