عنوان

Geology, Geochemistry, Ore controlling Parameters and genesis of Barite-(Cu-Zn-Pb-Au –Ag) mineralization in the late Proterozoic volcano-sedimentary sequence, southwest of Mahabad

شماره

T26688

زبان متن نوشتاري يا گفتاري و مانند آن

انگلیسی

عنوان اصلي

Geology, Geochemistry, Ore controlling Parameters and genesis of Barite-(Cu-Zn-Pb-Au –Ag) mineralization in the late Proterozoic volcano-sedimentary sequence, southwest of Mahabad

نام عام مواد

Dissertation

نام نخستين پديدآور

Somayeh Sharifiyan

نام ناشر، پخش کننده و غيره

Natural Sciences

تاریخ نشرو بخش و غیره

1400

نام خاص و کميت اثر

179p.

ساير جزييات

cd

جزئيات پايان نامه و نوع درجه آن

Ph.D.

نظم درجات

Geology (Economic Geology)

زمان اعطا مدرک

1400/11/23

متن يادداشت

The southwestern part of Mahabad town in the northwestern part of the Sanandaj-Sirjan metamorphic zone (SSZ) of Iran hosts seven barite-base metal deposits. They have occurred within the Precambrian-aged metasedimentary succession including black color fine-grained shale, slate, and phyllite with minor calcareous intercalation. This investigation is focused on three main ore deposits including Meraneh, Sorkhab, and Shekarbeig. The mineralized units and host rocks have been metamorphosed to lower greenschist facies in the Post-Cretaceous.Five different stages of mineralization were distinguished based on the field observations, mineralogical and textural relationships, morphology of the orebodies, and mineral chemistry studies. The followings are the stages of evolution: (1) precipitation of framboidal, colloform, and monomineralic pyrite bands and fine-grained barite (2) stratiform accumulation of barite with sulfide and un-mineralized sediment strata (3) stockwork mineralization and associated alteration (4) formation of discrete vent complex associated with massive sulfides and barite in replacement zone, and (5) post-mineralization deformation and shearing process, contemporaneous with regional metamorphism.Pyrite, chalcopyrite, sphalerite, and galena are the major sulfide minerals, in order of abundance, found in the studied deposits, accompanied by the minor amounts of tetrahedrite and covellite. The stratiform, massive and stockwork ores are indicative of the main ore-forming event and are volumetrically the most important facies. The electron probe micro-analyzer (EPMA) data of sulfide minerals indicates a distinct variation in trace element concentrations during the ore formation. Besides, this study focuses on distributions of δ 34S value in sulfide minerals, as well as δ34S and δ18O value of barite mineralization in stratiform, stratabound, and stockwork ore zones. The paragenetic relationships, mineral chemistry and isotopic study of minerals reveal that the stages 1 and 2 can be considered as the pre-date hydrothermal input of the stage 3 in all the three ore deposits. In addition, the mineralization event during stage 1 of the ore formation was found out to have occurred in a low temperature environment within the unconsolidated sediments, instantly under the sea floor. During stage 2, the stratiform ore has been deposited due to the diagenetic processes. The up-flow exhalative hydrothermal fluids resulted in the thermal alteration of the organic-rich host rock during stage 3, and formation of the massive mineralized bodies in stage 4. Finally, the lower greenschist facies metamorphism affected both the ore and host rocks during stage 5.dHigher LREE/HREE ratios, Al2O3/TiO2 ratios, Cr and Ni content, trace element ratios La/Sc, La/Co, Th/Co, Th/ Sc, Cr/Th and Th/Cr revealed sediments in the host sedimentary rocks may mainly be from felsic rocks.The geochemical compositions of sedimentary rocks support passive continental margin setting of the provenance. The V/(V+Ni), Ni/Co, V/Cr and V/Sc values, Mo concentration, Eu and Ce anomalies, Mn and Fe contents, and V versus Ni have been used to distinguish the redox state of sedimentary rocks that host mineralization. Accordingly, studied samples shows that the sediments were deposited under oxic to anoxic condition.On the basis of mineral chemistry inspections, all types of pyrites have high Ni and low Co contents and great majority of them show the Co:Ni ratios of lower than 1. Stratiform pyrites were fine-grained and enriched in As, Au, and Co, in contrast to hydrothermally pyrites. Ni, Pb, Zn, Bi, Hg, and Cu were mostly concentrated in coarse-grained hydrothermally pyrits. Also, the temperature and sulfur fugacity increased from stratiform stage to hydrothermal stage. The Se content of chalcopyrite as well as Bi and Ag contents of Galena increased from feeder to massive and stratiform ore. Sphalerite was generally iron-poor and its Fe content decreases from feeder to massive and stratiform ore. The Co/Ni ratio of pyrite and Zn/Cd ratio of sphalerite can be used to discriminate the VMS, magmatic or SEDEX origins for ore deposits. The Zn/Cd ratio of the sphalerites and Co/Ni ratio of pyrites provided the evidence for SEDEX style mineralization in the studied deposits.The geochemistry of the Rare Earth Elements, such as low ΣREE concentrations, LREE-enriched chondrite-normalised REE patterns, the negative Ce and positive Eu anomalies, and the low Ce/La ratio suggest that the barite was deposited from hydrothermally influenced sea water. So it is thought, in diagenetic stage, where Ba-rich pore waters migrate under reducing conditionsand react with sulfate ions in oxic sediments or at the sediment–seawater interface and precipitate as barite in relation to the increase in Eh is the plusible mechanism of early diagenetic barite deposition. In hydrothermal stage, barite was dissolved by moderate salinity fluids under reducing conditions and Ba+2 was transported and reprecipitate on the seafloor where the ascending Ba-bearing hydrothermal fluids encountered the seawater. Mixing with seawater and decrease in the temperature of the hydrothermal fluids was responsible for the formation of the massive barite.Barites with various textures and morphologies show overlapped distributions of δ34S and δ18O values from the stages 2, 3, and 4, range from +28.7 to +35.6‰ and +17.8 to +21.5‰, respectively. The δ 34S versus δ 18O patterns for stratiform barite resemble patterns that indicate sulfate is consumed by AOM. Sulfides have different isotopic compositions: stratiform with markedly more positive δ34S values of +31.6‰ to +33.5‰; stockwork with δ34S values of +24.1‰ to +32.7‰; and massive with δ34S between +16.6‰ and +24.8‰. It seams that the isotopic relationships (δ34S pyrite ≈ δ34S barite) in the stratiform ore zones may be related to anaerobic oxidation of methane coupled to sulfate reduction (AOM-SR), which has been developed during open system diagenesis. Textural and isotopic evidence indicate that the stockwork and massive ores has grown by thermochemical sulfate reduction (TSR) and reductively dissolving barite. On the other hand, the trend between δ 18O and δ34S suggest that the growth of the stockwork and massive barite is related to fluid seep on modern continental margins.eFluid inclusions in barit related to stratiform, massive and stockwork ore facies that are cogenetic with sulfide minerals in the main stage of mineralization, were studied by microthermometry. Investigation of the ore fluid reveals, stratiform barite, interlayered with sulfides form at relatively low salinity (<4.64) and low temperatures (<183 °C), stockwork and massive barite form at moderately high salinity (12.45-13.93; 9.98-12.42, respectively) and high temperatures (182–268 °C; 172-249, respectively). This finding suggests diagenetic condition for stratiform ore and massive barite probably arose from Selwyn-Type sedimentary exhalative hydrothermal fluids and are more like the vent-proximal sedimentary-exhalative (SEDEX) deposits. Fluid cooling and/or mixing with seawater could be the significant mechanisms that prompted the ore formation.

متن يادداشت

جنوب¬غرب مهاباد، شمال¬غرب زون دگرگونی سنندج-سیرجان (SSZ) چندین کانسار باریت-فلزات پایه را در ایران میزبانی می¬کند. این کانسار¬ها که در 54 کیلومتری جنوب¬غرب شهر مهاباد قرار دارند شامل کانسارهای مرانه، شکربیگ، سرخاب، محمودآباد، میریسه، گاگیش اولیا و گاگیش سوفلا می¬باشند. منطقه مهاباد با دارا بودن 22 درصد از معادن باریت کشور و پتانسیل بالا برای اکتشاف باریت مورد توجه بوده است (Bahrami et al., 2018). علاوه بر کانسارهای مورد مطالعه (جنوب غربی مهاباد)، چندین کانسار باریت دیگر نیز در شمال شرقی منطقه مهاباد وجود دارد که سنگ‌های میزبان متفاوتی دارند (Behyari et al., 2019). معادن باریت در این منطقه با ذخیره کل 5/3 میلیون تن، 40 درصد کل باریت مصرفی در عملیات حفاری در ایران را تولید می¬کنند (Bahrami et al., 2018).این مطالعه بر روی سه کانسار اصلی شامل مرانه، سرخاب و شکربیگ متمرکز شده است. فعالیت‌های معدنی در این کانسارها از حدود 13 سال پیش آغاز شده و به‌صورت روباز برداشت می¬شوند. عرض و طول سینه¬کارها به ترتیب از 10 تا 100 و 500 تا 1000 متر می‌باشد. لازم به ذکر است که منطقه مورد مطالعه به دلیل قرار گرفتن در مجاورت مرز ایران و عراق بسیار ناامن و صعب¬العبور می¬باشد، که مانع اصلی برای دانشگاهیان و شرکت‌های معدنی برای انجام فعالیت‌های تحقیقاتی و اکتشافی می¬باشد. بااین‌حال، استخراج بیشتر توسط مردم محلی انجام می¬شود. ازاین‌رو تاکنون مطالعات دقیقی روی این ذخایر انجام نشده است و اطلاعات منتشرشده¬ای از تناژ و عیار این ذخایر معدنی در دسترس نیست. بنابراین کار فعلی به درک بهتر پیدایش کانی سازی باریت -فلز پایه در این منطقه با پیامدهای مهم برای اکتشاف ذخایر جدید در شمال غرب ایران کمک می¬کند.

عنوان گونه گون

" زمینشناسی، ژئوشیمی، عوامل کنترل کننده کانهزایی و ژنز ذخایر باریت ) مس–روی– سرب–طلا و نقره( در توالی آتشفشانی–رسوبی پروتروزوئیک بالایی، جنوبغرب مهاباد "

اصطلاح موضوعی

Mahabad, Sanandaj-Sirjan, Kahar Formation, Iran, stratiform barite and sulfide, diagenesis, SEDEX

اصطلاح موضوعی

فاقد کلید واژه فارسی

عنصر شناسه اي

Sharifiyan,

ساير عناصر نام

Somayeh

کد نقش

Producer

عنصر شناسه اي

Hosseinzadeh,

عنصر شناسه اي

Moayyed,

عنصر شناسه اي

Maghfouri,

ساير عناصر نام

Mohammad Reza

ساير عناصر نام

Mohsen

ساير عناصر نام

Sajjad

کد نقش

Thesis advisor

کد نقش

Consulting advisor

کد نقش

Consulting advisor

عنصر شناسه اي

Tabriz

کشور

ایران

سازمان

Center library of tabriz

تاريخ عمليات

20220620

شماره بازیابی

دکتری پایاننامه QE307.Sh3 1400

نام الکترونيکي

Somayeh Sharifiyan

ارتباط براي تسهيلات دسترسي

قاسمی

فرمت انتشار

e

نوع ماده

TL

کد کاربرگه

276903

سطح دسترسي

a

تكميل شده

Y