ویژگی‌ های کانی‌ شناسی، بافتی و میان‌ بارهای سیال در زون سیلیسی میده، شمال پاریز، کمربند مس کرمان: بررسی ارتباط زایشی با سامانه‌ های پورفیری

زون‌های سیلیسی با ابعاد متفاوت در کمربند ماگمایی کرمان وجود دارد که ممکن است برخی نشان‌دهنده لیتوکپ در سامانه‌های مس پورفیری باشد. برای بررسی این پتانسیل، یک زون سیلیسی در سنگ‌های آندزیتی ‌بازالتی در منطقه‌ میده در شمال پاریز و برای مقایسه، زون‌های سیلیسی در حاشیه سامانه مس پورفیری سریدون و یک سامانه رگه در شرق سرچشمه بررسی شده است. زون سیلیسی میده بافت‌های توده‌ای، برشی و به‌ طور محلی حفره‌ای دارد و با هاله‌ای از دگرسانی سیلیسی-رسی فراگرفته شده است. رخنمون‌های کوچک و پراکنده‌ کوارتز تورمالین نیز وجود دارد. هاله سیلیسی-رسی علاوه‌بر کوارتز حاوی کائولینیت و ایلیت است. زون‌های سیلیسی در سریدون و شرق سرچشمه، بافت‌ غالب توده‌ای و برشی دارند. در سریدون بافت حفره‌ای نیز توسعه یافته است. میان‌بارهای سیال در میده، سریدون و شرق سرچشمه اغلب دوفازی مایع بخار غنی از مایع است. میانگین دمای همگن‌شدن به‌ترتیب 202، 247 و 177 درجه‌ سانتی‌گراد و میانگین شوری 1.62، 2.27 و 1.57 درصد وزنی معادل نمک‌ طعام است. سنگ کوارتز تورمالینی حاوی میان‌بارهای چندفازی نیز است. میانگین دمای همگن‌شدن و شوری برای میان‌بارهای دوفازی به‌ترتیب 231 درجه سانتی‌گراد و 5.43 درصد وزنی معادل نمک‌ طعام و برای میان‌بارهای هالیت‌دار 382 درجه‌ سانتی‌گراد و 47 درصد وزنی معادل نمک ‌طعام است. با توجه به شواهد بافتی و کانی‌شناسی، زون سیلیسی میده در تراز کنونی نمی‌تواند بیانگر لیتوکپ مرتبط با سامانه پورفیری باشد. رخداد کوارتز تورمالین می‌تواند نشان‌دهنده ارتباط با سامانه‌های ماگمایی باشد؛ اما این رخداد محلی است و نمی توان آن را تعمیم‌داد.

The mineralogy, texture and fluid inclusion characteristics of Meideh silicic zone, north Pariz, Kerman copper belt; investigation of genetic relations with porphyry systems

IntroductionThe widespread Cenozoic magmatic assemblages in Iran host a variety of ore deposits including porphyry CuMoAu, skarn type ores, and epithermal base and precious metals deposits. Silicic zones of variable sizes are common in the Kerman belt in the southern section of the UrumiehDokhtar arc, and some might be representing the upper parts of porphyry copper systems known as lithocap. To investigate this potential relation, a silicic zone in Meideh, north Pariz, is studied. The silicic zone lies in an area with several known porphyry copper deposits (PCD) including Sarcheshmeh, Nochun, Seridun, Sarkooh, and BaghKhoshk. For comparison, silica ledges and veins in Seridun and a mineralized silica vein system to the east of the Sarcheshmeh mine are also studied. Materials and methodsThe study is based on field studies and investigation of textures and structures, and sampling for mineralogy (microscopic and Xray diffraction analysis), and fluid inclusions. The XRD analyses were accomplished in the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and Kansaran Binaloud Co, Tehran. The fluid inclusion studies were performed in the Iranian Mineral Processing Research Center (IMPRC) using a Linkam THMS600 equipped with a Zeiss microscope.ResultsThe silicic zone in Meideh is developed in andesitic lava flows and pyroclastic materials, and covers an area of ~ 1 km2. Silica occurs in white to grey colors and in massive, brecciated and locally vuggy textures; the grain sizes range between 0.01mm to 1mm. The silica is locally associated by minor sulfides (pyrite and locally chalcopyrite) carbonates, and clay minerals.The silicic zone grades outward into a silicicargillic halo and into the host volcanic rocks with propylitic alteration. Chemical analysis of samples from the zone indicated enrichments in Cu, Mo, Ag, As, Bi and Au relative to the average composition of intermediatemafic volcanic rocks in the Kerman belt. Small outcrops of a quartztourmaline rock occur in the southeast of the silicic zone.In Seridun, silica ledges and veins occur in the periphery and in the upper parts of a porphyry copper deposit developed in Miocene shallow intrusive bodies and older volcanic rocks. In east of Sarcheshmeh, several NS striking silica veins locally containing pyrite, chalcopyrite, malachite, and Feoxides/hydroxides occur in Cenozoic volcanic and intrusive host rocks. In both areas, the silicic zones are products of pervasive silicic alteration, and occur in massive, breccia, and vuggy textures. Vuggy texture is well developed in Seridun. XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun.Fluid inclusions in quartz from all three areas are dominated by twophase liquidvapor. Homogenization temperature (TH) varies between 140263 oC (average: 202 oC) for Meideh, 195320 oC (average: 247 oC) for Seridun, and 140264 oC (average: 177 oC) for east of Sarcheshmeh. Salinities vary between 0.185.71 (average: 1.62), 1.224.18 (average: 2.27), and 0.73.39 (average: 1.57) wt.% NaCl eq., respectively. The quartztourmaline rock from Meideh is distinguished by the occurrence of liquidvaporhalite±hematite and liquidvaporopaque inclusions, in addition to liquidvapor inclusions. The TH and salinity for the liquidvapor inclusions, homogenizing to liquid, varies, respectively, between 202269 oC (average: 231 oC) and 3.717.16 (average: 5.43) wt.% NaCl eq. The TH and salinity for the halite bearing inclusions, homogenized by halite dissolution, varies between 240480 oC (average: 345 oC) and 33.4056.90 (average: 42.80) wt.% NaCl eq. DiscussionThe textures, structure, and spatial relations with the host volcanic rocks suggest that the Meideh silicic zone developed as a result of pervasive silicic alteration, rather than open space filling. Textures indicative of open space filling, including crustification and symmetric banding, are absent in Meideh. The silicic ledges in Seridun, and the NS striking silicic zones in east of Sarcheshmeh, are the products of pervasive silicic alteration of the host volcanic and intrusive rocks.The XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from the three silicic zones are dominated by twophase liquiddominant LV inclusions. No distinction in salinity can be made between the three zones; Seridun, however, is distinguished by higher homogenization temperature. The local quartztourmaline zones in Meideh developed from distinctly higher temperature and salinity fluids (240480 oC and 33.964 wt.% NaCl eq., respectively). A comparison of fluid inclusion data with several epithermal base and precious metals systems in the UrumiehDokhtar arc and elsewhere in Iran suggest that no meaningful distinction can be made between barren (i.e. Meideh, at current exposure level) and productive epithermal systems.Our data indicate that the silicic zone in Meideh cannot be considered as a porphyryrelated lithocap at current exposure. The quartztourmaline rock developed from fluids of higher salinity and temperature suggests a link with magmatichydrothermal systems and warrants further investigation. AcknowledgementsWe would like to thank Mr. Afrouz for introducing the area, help with field works, and discussions. We are grateful to Mr. Imani from Parsolang for his help with field works and discussions, and to Ms. Aghajani from Iranian Mineral Processing Research Center for her invaluable help with the fluid inclusion studies. Dr. Ashrafpour kindly provided us with geological maps and chemical analysis of samples from the Meideh silicic zone. The study was supported by the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and a Shahid Beheshti University grant to S.A.