زمین شناسی و ژئوشیمی کانه‌زایی منگنز در شوراب کبیر، (شمال شرق شهرکرد) زون سنندج سیرجان

کانسار منگنز شوراب کبیر، در 60 کیلومتری شمال شرق شهرکرد، بخش میانی زون سنندج سیرجان واقع شده است. قدیمی ترین سنگ های منطقه شامل شیل، ماسه سنگ، آهک و دولومیت های دگرگون شده پرمین می باشند. واحدهای پرمین بواسطه عملکرد گسل های رانده بر روی واحدهای جوانتر، شامل واحدهای شیل، ماسه سنگ و کنگلومراهای با میان لایه های آندزیتی ژوراسیک رانده شده اند. کانه زایی درون واحدهای کربناته به صورت رگ های، توده ای و داربستی رخ داده است. کانه زایی اغلب به صورت کانه های پیرولوزیت، پسیلوملان، منگانیت و گوتیت، هماتیت، مگنتیت همراه با کلسیت وکوارتز می باشد. دگرسانی های موجود در منطقه کربناتی و سیلیسی می باشند. الگوی بهنجار شده عناصر نادر خاکی با گوشته اولیه دال بر آنومالی منفی ce بواسطه محیط اکسیدان و اسیدی، و آنومالی منفی ضعیفی از eu بواسطه فاصله گیری سیال گرمابی از منشاء می باشد. در الگوی بهنجار شده عناصر جزیی نمونه های مطالعه شده به گوشته اولیه، غنی شدگی از ba, la, sr, pb و تهی شدگی از ce, nb, ti, nb, rb قابل مشاهده است. کلیه داده های صحرایی، میکروسکوپی و ژئوشیمیایی دال بر دخالت سیالات گرمابی در تشکیل کانسار شوراب کبیر می باشد.

geology and geochemistry of the shurab kabir mn mineralization, north shahrekord, sanandaj-sirjan zone

shurab kabir mn occurrence, 60km northeast of shahrekord, is located in the sanandaj–sirjan zone. manganese deposits occur in various tectonic settings, with ore deposits associated with ophiolites and continental sedimentary sequences. these deposits can be divided into three types based on mineralogy, geochemical composition and tectonic setting: (1) hydrogenous, (2) hydrothermal, and (3) diagenetic/biogenetic-bacterial deposits (hein et al., 1997; öksüz, 2011; polgári et al., 2012). since the sanandaj-sirjan zone is an intercontinental rift, magmatic and metamorphic phenomena are essential in forming mineral deposits (hedayati roshan, 2014). ghorbani (2011) divides the sanandaj-sirjan zone into three parts from the perspective of economic geology and the distribution of deposits. the southern part includes deposits of chromium, iron, manganese, lead, zinc and copper, the middle part contains deposits of lead, zinc, silver, iron, manganese and gold, and the northern part due to the presence of iron, gold, antimony and aluminium ores are essential. the study area is located in the middle part of the sanandaj-sarjan zone, at the latitude of 32° 29.53' n and the longitude of 50° 59.443ˊ e (alavi, 2004; fig. 1). the north of shahrekord was investigated to identify anomalies of copper, gold, iron, cobalt, zirconium and lead (hedayati roshan, 2014). also, pb mineralization in the north of shahrekord has been studied by (ahankoub et al., 2018). nasiri (2017) studied the fe-cu mineralization in the hooreh area, north shahrekord, but there is no report about mn mineralization in this area. the present paper provides an overview of the geological framework, the mineralization characteristics, and the geochemical features of the shurab kabir mn occurrence with an application for the ore genesis.2- materials and methodsa number of 73 samples of massive, layered and banded ores were collected in the field. in addition, 30 thin sections and 12 polished-thin sections from host rocks and mineralized samples were studied by conventional petrographic and mineralogical methods at the university of payam-e-noor of shahrekord. in addition, xrf and icp-ms analyzed the least-altered five samples for major and trace elements and ree compositions at binalood laboratory, tehran, iran. then all the data were processed and interpreted with gcdkit, triplot and excel software.3-results and discussionthe host rocks at the shurab kabir area consist of metamorphic rocks before permian, permian limestone and dolomite, jurassic shale, marls, limestone, sandstone, conglomerate and volcanic rocks, miocene-pliocene limestone and quaternary terraces. mn mineralization at shurab kabir occurs as nw-se- trending lens, veins and mass with different thicknesses of 3 to 5.5 meters with a length of more than 500 meters. the central part of mineralization is inside the marble units and metamorphosed dolomites, and the part is at the boundary of the layers.dominant alteration is carbonation and silicification in the study area. primary mineralization consists of pyrolusite, psilomelane, and manganite with iron oxides and hydroxides formed by the hydrothermal fluid at the primary stage. also, silica and calcite veins are formed in the later hydrothermal stage