Multistage Neoproterozoic granitic magmatism and formation of Yidong tin deposit in northern Guangxi, China

A number of Sn deposits associated with Neoproterozoic granites are located in the western Jiangnan Orogen of northern Guangxi. The distribution of Sn mineralization is controlled by faults occurring within and around the Neoproterozoic granites. The hydrothermal alteration and mineralization of these Sn deposits exhibit zoning from the granite to the wall rock. The laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb ages of the cassiterite and zircon from ore-bearing granite in the Menggongshan Sn deposit are 829 ± 19 Ma and 822 ± 4 Ma, respectively, indicating that the Sn mineralization and granites formed in the Neoproterozoic and can considered to be products of coeval magmatic and hydrothermal activities. The ore-bearing granite and Neoproterozoic granites in northern Guangxi are high-K, calc-alkaline, peraluminous, S-type granites that are depleted in Nb, Ti, Sr and Ba and highly enriched in Rb, U and Pb. All the granites show steep fractionated light rare earth element (LREE) and flat heavy rare earth element (HREE) patterns, with strongly negative Eu anomalies. The eHf(t) values of the ore-bearing granite vary from − 9.0 to − 1.7, with an average value of − 4.1. Additionally, the ore-bearing granite exhibits low oxygen fugacity values. The magmatic source experienced partial melting during their evolution, and the source was dominated by recycled heterogeneous continental crustal materials. Our evidence confirms that the Neoproterozoic granites in northern Guangxi formed in a collisional tectonic setting. The collision between the Cathaysia and Yangtze blocks or between the Sibao arc (Jiangnan arc) and the Yangtze Block caused asthenospheric upwelling, leading to partial melting and recycling of the crust, forming the peraluminous S-type granites in the Neoproterozoic. The Sn mineralization has a close genetic relationship with the Neoproterozoic granite. The highly differentiated, peraluminous, B-enriched, crustally derived Neoproterozoic granites provided the heat source and ore-forming material for the Sn mineralization. Furthermore, the low oxygen fugacity of these Neoproterozoic granites also favoured the Sn mineralization.

Metallogenesis of the Siding Pb-Zn deposit in Guangxi, South China: Rb-Sr dating and C-O-S-Pb isotopic constraints

Tourmaline is a common mineral in a variety of hydrothermal ore deposits (Slack 1996). Thanks to its wide P-T stability, resistance to weathering, variable composition, common presence of zoning and the dominant mineral host for boron in most crustal rocks, tourmaline not only can preserve a very good record of the composition of the fluid from which it crystallized, but also can trace the direction of fluid evolution (Trumbull et al., 1999, 2008). The Jiuwandashan-Yuanbaoshan area of Nouthern Guangxi is the oldest tin polymetallic region in South China. Tourmaline widely distributed from granite to oreforming hydrothermal vein and part in Sibao Group in this area. In this study, we focus on the chemical and boron isotopic composition of tourmaline in Pingying granite pluton and the related tourmaline type tin deposit in Baotan by Electron Microprobe and in-situ B isotopic analyses using LA-MC-ICP-MS. 2 Geological Setting Baotan tin deposit is located in the JiuwandashanYuanbaoshan region, Northern Guangxi, South China. It is in the western part of the Jiangnan Orogenic Belt, closely to the tectonic suture zone between the Yangtze and Cathaysia Blocks. The deposit is mainly controlled by a series of subparallel, NE-trending fractures and ore veins along its distributions, which are centered in the southeast margin of Pingying granitic pluton. This pluton, which has an outcrop area of ~15 km

The relationship between ductile shear zone and mineralization in the Jiufeng Sn deposit, northern Guangxi, South China: Evidence from structural analysis and cassiterite U-Pb dating

China is rich in tin resources, and contains many types of tin deposits. Among the tin deposit types, the cassiterite‐sulfide type, skarn type and quartz vein type occupy a large proportion of tin resources and reserves. From the aspect of exploitation and utilization, the most important types are cassiterite‐sulfide type and quartz vein type. The cassiterite‐sulfide type tin deposits are mainly located in Northern Guangxi and Eastern Yunnan, skarn type deposits are mainly distributed in the ore‐concentration areas of South Hunan in Middle Nanling, and the quartz vein type tin deposits are mainly distributed in South China, such as Western Fujian, Middle Jiangxi, Northern Guangzhou and Southern Hunan. The most important metallogenic epoch for tin deposits is the Mesozoic era. The metallogenic geotectonic background is mainly continental environments after orogeny process, with strong tectonic changes, interlaced deep fracture and frequent magmatism. And the most distinctive feature is the well developed Mesozoic granites, which have a close relationship with tin mineralization. Based on the detailed study of the data from 873 tin deposits in China, this paper summarized the metallogenic regularity of tin deposits, classified 20 important metallogenic series of tin or tin‐associated deposits, and inferred that the cassiterite‐sulfide type, skarn type, quartz vein type and greisen type are the main prediction types of tin resources. Forty‐four tin‐mineralization belts were divided, among which, 19 belts are the most important. In addition, a series of maps about tin metallogenic belts and tin metallogenic regularity were compiled, aiming to provide theoretical basis for potential estimation and prediction of tin mineral resources.

Tourmaline as an indicator for late-magmatic to hydrothermal fluid evolution of the Neoproterozoic Baotan tin deposit, South China

Neoproterozoic chromite-bearing high-Mg diorites in the western part of the Jiangnan orogen, southern China: Geochemistry, petrogenesis and tectonic implications

U–Pb zircon ages of granites from the southern margin of the Yangtze Block: timing of Neoproterozoic Jinning: Orogeny in SE China and implications for Rodinia Assembly

The extensive development of tourmalinite is a feature that distinguishes the northern Guangxi polymetallic tin province of China from similar metallogenic provinces elsewhere. Two types of tourmalinite occur in the province. The first type, in the lower part of the Early Proterozoic Sibao Group, is bedded, stratiform or lenticular tourmalinite that shows well-developed laminated, gel, and degelatinized structures. Its mineral assemblage is very simple and the grain size ranges from 2 to 8 μm. This tourmaline is relatively rich in Mg, with an Fe/(Fe + Mg) ratio of 0.25–0.50. The second type of tourmalinite occurs as lodes distributed in the exocontact zone of Late Proterozoic biotite-granite intrusions. Its mineral assemblage is relatively complex; the tourmaline is present as euhedral or subhedral crystals ranging from 0.1 to 3.5 mm, mostly from 0.5 to 1 mm. This tourmaline commonly exhibits a radiating, zoned structure with Fe/(Fe + Mg) ratios of 0.64–0.79. It is suggested that the bedded tourmalinite formed by exhalation in an Early Proterozoic spreading-ridge environment, whereas the vein tourmalinite formed in a plate-convergence setting genetically associated with emplacement of Late Proterozoic biotite granite. As the tourmalinites themselves are related to mineralized rocks and orebodies, their origin and the related boron cycle of the region reflect to some extent the formation and evolution of the associated polymetallic tin deposits of the region.

Neoproterozoic mineralization in a hydrothermal cassiterite-sulfide deposit at Jiumao, northern Guangxi, South China: Mineral-scale constraints on metal origins and ore-forming processes

The Baotan tin deposit (23 Mt @ 0.43% Sn) is located in the Jiuwandashan–Yuanbaoshan area, South China. It is hosted in Neoproterozoic mafic/metasedimentary rocks and apical portions of the Pinying granite pluton. Six alteration and mineralization stages have been identified: pre-ore alteration, cassiterite greisen, cassiterite–tourmaline–quartz vein, cassiterite–quartz vein, cassiterite–sulfide vein, and post-ore quartz/calcite–quartz vein stages. Tin mineralization is mainly in the cassiterite greisen, cassiterite–tourmaline–quartz, and cassiterite–quartz vein stages. The deposit is characterized by widespread tourmalinization. Both pre-ore and ore-stage tourmaline is schorl. Tourmaline from pre-ore tourmaline–quartz nodules has elevated Al2O3 and F contents and Fe/(Fe + Mg) and Na/(Na + Ca) ratios, which are probably controlled by the initial magmatic fluid. Ore-stage tourmaline shows low Al2O3 and F contents and Fe/(Fe + Mg) and Na/(Na + Ca) ratios, which are likely influenced by the surrounding mafic rocks. LA–ICP–MS U–Pb dating on two cassiterite samples from disseminated cassiterite–tourmaline–quartz ore and cassiterite–quartz vein yields 206Pb/238U weighted mean ages of 832 ± 5 Ma and 834 ± 4 Ma (2 σ), respectively. These two dates are consistent with the previously reported zircon U–Pb ages of 834–835 Ma for the Pingying granite, which indicates that tin mineralization is related to the granite. The granite has low magnetic susceptibility and zircon Ce4+/Ce3+ ratios, which are similar to those of Sn-bearing ilmenite-series granites. Our study confirms the Neoproterozoic tin mineralization event in South China and indicates that the Neoproterozoic highly fractionated S-type granites in the southeastern margin of Yangtze Block have a great potential for tin mineralization.

The early Paleozoic tectono-magmatic activity within the South China block, which is well illustrated by Ordovician–Devonian granites in the western Qinhang belt, was the response to closure of the Proto-Tethys Ocean and convergence of continental blocks. The spatiotemporal distribution and source characteristics of the granites provide us the opportunity to understand the processes and driving mechanisms of intracontinental orogeny. As an example, the Miaoershan-Yuechengling granite batholith in northern Guangxi, located along the western margin of the Qinhang orogenic belt, is mainly composed of quartz monzonite and monzogranite. All the granitic rocks from Miaoershan-Yuechengling batholith are composed of K-feldspar, quartz, plagioclase, biotite, and hornblende. Geochronologic dating indicates that the Miaoershan-Yuechengling batholith was emplaced during the late Silurian and Early Devonian, respectively. The rocks have high SiO2, with an average value of 73.29 wt%, and total alkalis (Na2O + K2O = 7.21–10.03 wt%), but low Al2O3 (12.96–15.51 wt%), showing characteristics of the high-potassium calc-alkaline series of S-type peraluminous granites (Al2O3/[CaO + Na2O + K2O] = 1.03–1.22). Trace elements in the Miaoershan-Yuechengling granitic rocks are characterized by enrichment of large ion lithophile elements and depletion of high field strength elements. Their rare earth element (REE) trends are characterized by relatively flat distribution patterns with weak light REE enrichment, weak heavy REE fractionation, and negative Eu anomalies. Zircons from the rocks have negative εHf(t) values ranging from −13.24 to −5.1, with crustal model ages (THf2) of 2.2–1.7 Ga. These features indicate that they are S-type granites with parental magmas originating from partial melting of sandy argillaceous sources of Paleoproterozoic lower continental crust. The thermal budget for Ordovician to Early Devonian magmatism is attributed either to crustal thickening in relation to intracontinental orogenic compression or to crustal thinning due to postorogenic tectonic extension during assembly and breakup of Greater Gondwana. This study reveals that the change in mantle convection systems during plate interactions acted as a major driving force for the early orogenic processes, late collapse of the orogenic belt, and massive syncollisional to postorogenic magmatism.

زون متالوژنی بافق- ساغند در ایران مرکزی میزبان کانسارهای عظیم اکسید آهن- آپاتیت (IOA) با Ti کم و یا به عبارتی کانسارهای آهن تیپ کایروناست که حدود 1500 میلیون تن سنگ آهن با عیار میانگین 55 % را شامل شده‌اند که می‌توان به کانسارهای چادرملو، چغارت، سه‌چاهون و اسفوردی اشاره کرد. منشأ این کانسارها مدت‌ها مورد بحث بوده و نظرات متعددی از جمله ماگمایی، هیدروترمال، کربناتیتی، سازند آهن نواری و رسوبی- بروندمی در این باره ارائه شده است. با توجه به مطالعات صورت گرفته تغیرات مقادیر 18O در کانی مگنتیت به عنوان جزو اصلی کانسارهای مورد مطالعه کاملا سیستماتیک و حاصل فرایندهای مؤثر در شکل‍گیری آن است. لذا در این مقاله به جهت بررسی منشأ کانسارهای اکسید آهن- آپاتیت ± عناصر نادر خاکی در محدوده بافق- ساغند از داده‌های ایزوتوپ پایدار 18O از کانی مگنتیت 4 کانسار چادرملو، چغارت، سه‌چاهون و اسفوردی استفاده شده است. مقدار18Oδ بین 1/0- و 2/2+ ‰ در مگنتیت‌های مورد مطالعه، نقش فرایندهای ارتوماگمایی (بیش از 9/0 ‰) و فرایندهای هیدروترمال (کمتر از 9/0 ‰) را در تشکیل این کانسارها نشان می‌دهد. از طرفی مقادیر کمتر از 3/0+ ‰ را می‌توان به اکسیداسیون ثانوی، هیدروترمال و یا ترکیبی از این دو فرایند نسبت داد. داده‌های به دست آمده مطابق با کانسارهای کمربند آهن ال‌لاکو در شیلی، کایرونا و گرانگزبرگ در سوئد و ژیبو و چاگانگنوئر در چین است که منشأ ماگمایی- هیدروترمال دارند. در نتیجه، با توجه به زمین‌شناسی و ماگماتیسم محدوده‌ بافق- ساغند در ابتدا طی فرایند ماگمایی در ارتباط با نفوذی‌های تونالیت- ترونجمیت- گرانودیوریت، دیوریت و گرانیت، مرتبط با فرورانش حاشیه‌ قاره به سن 525 تا 532 میلیون سال قبل کانی‌زایی اصلی شکل گرفته است. سپس فرایندهای هیدروترمال وابسته به نفوذ توده‌های آلکالن (سینیت و مونزوسینیت) منجر به شکل‌گیری فاز هیدروترمال شده است. لذا می‌توان گفت تشکیل کانسارهای اکسید آهن- آپاتیت با Ti کم در زون بافق- ساغند در ارتباط با فرایند ماگمایی- هیدروترمال بوده است.

Spatiotemporal distribution, geological characteristics and metallogenic mechanism of tungsten and tin deposits in China: An overview

Indonesia is included in the East Malaya Block of the Southeast Asian Tin Belt. Two types of tin deposits in Indonesia are primary and secondary tin deposits (placer). Factors that can cause the formation of placer tin deposits include S-type granite, weathering, transportation, and sedimentation. Factors that control the formation of placer tin deposits include the presence of source rock (granite type S), weathering processes, erosion, transportation and sedimentation, and the presence of basins or valleys where weathering materials are deposited. The transportation process has a major role in the grain shape of a material. This study aims to determine the geochemical distribution and characteristics of heavy mineral grains at the accumulation of placer tin deposits, e.g., colluvial, alluvial, and tailings, in which there are 62 sample points located Bangka Island, Indonesia. The research method used in this study was grain size analysis, radiation level measurement using a scintillometer, and geochemical analysis using ICP-MS.