scholarly journals Early Jurassic Mafic Intrusions in the Southern Youjiang Basin, SW China: Petrogenesis, Tectonic and Metallogenic Implications

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 771 ◽  
Author(s):  
Wen Jiang ◽  
Quanren Yan ◽  
Li Deng ◽  
Bin Zhou ◽  
Zhongjin Xiang ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Tectonic Setting ◽  
Element Distribution ◽  
Early Jurassic ◽  
Trace Element Distribution ◽  
Sw China ◽  
Mafic Intrusions ◽  
Isotopic Analyses ◽  
Youjiang Basin ◽  
Back Arc

A suite of mafic intrusions, composed of diabase and micro-gabbro outcrops in the Jingxi area of southern Youjiang Basin, SW China. This study conducts geochronological, geochemical, and Sr–Nd isotopic analyses on the mafic intrusions in Jingxi with the aim of determining their petrogenesis, tectonic setting, and metallogenic implications. Zircon U–Pb dating for the mafic intrusions yielded an age of 183 ± 3 Ma (MSWD = 2.3), which is coeval with the Carlin-like gold mineralization in the Youjiang Basin. The mafic intrusions are alkaline in composition and characterized by low TiO2 (1.25–1.87 wt %) contents and low Ti/Y ratios (410–550). They exhibit OIB-like patterns of trace element distribution and they have low (87Sr/86Sr)i ratios of 0.704341 to 0.705677, slightly negative εNd(t) values of −0.30 to −2.16, low La/Ta (11.57–15.66) and La/Nb (0.77–1.06) ratios, with [La/Yb]N = 6.52–10.63. The geochemical characteristics, combined with regional considerations, suggest that the mafic intrusions originated from partial melting of upwelling asthenosphere within the garnet-spinel transition zone, as a result of intracontinental back-arc extension triggered by the steep subduction of the Paleo-Pacific plate beneath the South China Block. Moreover, the new data not only suggest Early Jurassic magma was a possible heat source, but also support a magmatism-related model for the Carlin-like gold mineralization in the Youjiang Basin.

scholarly journals Tectonics of Volcanogenic Massive Sulphide (VMS) Deposits at Flores Back Arc Basin: A Review

2020 ◽  
Vol 35 (2) ◽  
Author(s):  
Noor CD Aryanto ◽  
Hananto Kurnio
Keyword(s):  
Gold Mineralization ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Hydrothermal Activity ◽  
Basaltic Lava ◽  
Sulphide Deposit ◽  
Volcanogenic Massive Sulphide ◽  
Submarine Ridge ◽  
Vms Deposits ◽  
Back Arc

The bathymetry, petrology, marine magnetic, and seismic-SBP data have identified the northwest-southeast direction submarine ridge that shows hydrothermal activity. This activity occurred through Mount Baruna Komba, Abang Komba, and Ibu Komba. The volcanic rocks are andesite basaltic lava flows, tuff, and pumice. The andesite basaltic lava shows porphyritic, intergranular, intersertal to glomeroporphyritic textures. The rock composes anhedral minerals of k-feldspar, plagioclase, and pyroxene. These minerals present in small-sized, short prismatic dispersed in very fine groundmass minerals or glasses. Most of the volcanic rocks have experienced various degrees of alteration. The k-feldspar and plagioclase are most dominantly transformed into sericite, clay mineral, carbonate, epidote and oxide mineral, opaque mineral, and secondary plagioclase through the albitization process, while pyroxene replaced by chlorite. Other minerals are biotite and quartz, and base metals are present Cu, Zn, Ag, As, Pb, and gold. Mineralization categorizes as the phyllic zone, sub-prophylithic zone, and phyllic-potassic zone that formed at a temperature range of 250-400oC. The submarine hydrothermal alteration in the Komba Ridge is associated with a volcanogenic sulphide deposit controlled by crust thinning due to the crust rifts in the back-arc tectonic setting.

Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland

1999 ◽  
pp. 65-78
Author(s):  
Henrik Rasmussen ◽  
Lars Frimodt Pedersen
Keyword(s):  
Tectonic Setting ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
West Greenland ◽  
North West ◽  
North East ◽  
Metavolcanic Rocks ◽  
Arc Setting ◽  
Area North ◽  
Back Arc

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Rasmussen, H., & Frimodt Pedersen, L. (1999). Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 65-78. https://doi.org/10.34194/ggub.v181.5114 _______________ Two Archaean supracrustal sequences in the area north-east of Disko Bugt, c. 1950 and c. 800 m in thickness, are dominated by pelitic and semipelitic mica schists, interlayered with basic metavolcanic rocks. A polymict conglomerate occurs locally at the base of one of the sequences. One of the supracrustal sequences has undergone four phases of deformation; the other three phases. In both sequences an early phase, now represented by isoclinal folds, was followed by north-west-directed thrusting. A penetrative deformation represented by upright to steeply inclined folds is only recognised in one of the sequences. Steep, brittle N–S and NW–SE striking faults transect all rock units including late stage dolerites and lamprophyres. Investigation of major- and trace-element geochemistry based on discrimination diagrams for tectonic setting suggests that both metasediments and metavolcanic rocks were deposited in an environment similar to a modern back-arc setting.

Methylmercury and Trace Element Distribution in the Organs of Stenella coeruleoalba Dolphins Stranded on the French Mediterranean Coast

2014 ◽  
Vol 8 (1) ◽  
pp. 35-48 ◽  
Author(s):  
Emmanuel Wafo ◽  
Véronique Risoul ◽  
Thérèse Schembri ◽  
Véronique Lagadec ◽  
Frank Dhermain ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Marine Pollution ◽  
Element Distribution ◽  
Mediterranean Coast ◽  
Trace Element Distribution ◽  
Slight Reduction ◽  
Stenella Coeruleoalba ◽  
Contamination Levels

The main objective of this study was to evaluate the contamination by mercury (Hg), methylmercury (Me-Hg), cadmium (Cd), selenium (Se), zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) in dolphins stranded on the French Mediterranean coast. The distributions of these contaminants in the organs of dolphins have also been studied. Overall, contamination levels varied according to the following sequence: liver > kidney > lung > muscle, except for cadmium (kidney > liver > lung > muscle). Size and sex of animals were also considered. Young dolphins were less impacted with trace elements than adults, except for copper. Among the studied parameters, the most important appeared to be the size of mammals. In addition, in the case of mercury and selenium, the sex of mammals seemed to be also relevant. The correlations between the concentrations of trace elements suggest the existence of detoxification processes. Since 1990s, using dolphins for tracing marine pollution, a slight reduction in the burden of the considered trace elements could be noted.

TRACE-ELEMENT DISTRIBUTION IN GIANT SPODUMENE CRYSTALS IN GRANITIC PEGMATITES FROM THE BLACK HILLS, SOUTH DAKOTA AND NEWRY, MAINE

2019 ◽  
Author(s):  
Stephan R. Hlohowskyj ◽  
◽  
Mona-Liza C. Sirbescu ◽  
James J. Student ◽  
Niels Hulsbosch ◽  
...  
Keyword(s):  
South Dakota ◽  
Trace Element ◽  
Element Distribution ◽  
Black Hills ◽  
Trace Element Distribution ◽  
Granitic Pegmatites

scholarly journals Re–Os Pyrite Geochronological Evidence of Three Mineralization Styles within the Jinchang Gold Deposit, Yanji–Dongning Metallogenic Belt, Northeast China

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 448 ◽  
Author(s):  
Shun-Da Li ◽  
Zhi-Gao Wang ◽  
Ke-Yong Wang ◽  
Wen-Yan Cai ◽  
Da-Wei Peng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Northeast China ◽  
Gold Mineralization ◽  
Metallogenic Belt ◽  
Isotopic Analyses ◽  
Mantle Sources ◽  
Stage 1 ◽  
Geochronological Evidence ◽  
Gold Bearing

The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources.

Trace element distribution in mineral inclusions in zoned garnets from eclogites of the Atbashi Range (South Tianshan)

2014 ◽  
Vol 52 (11) ◽  
pp. 939-961 ◽  
Author(s):  
N. I. Volkova ◽  
S. V. Kovyazin ◽  
S. I. Stupakov ◽  
V. A. Simonov ◽  
K. S. Sakiev
Keyword(s):  
Trace Element ◽  
Element Distribution ◽  
Trace Element Distribution ◽  
Mineral Inclusions ◽  
South Tianshan

Mesozoic Tectonic Setting of SE Sundaland After Magmatism and Suture Evidences in JS-1 Ridge Area

2021 ◽  
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Tectonic Setting ◽  
Plate Boundary ◽  
Early Jurassic ◽  
The South ◽  
Magmatic Arc ◽  
Plate Convergence ◽  
Ridge Area ◽  
Cretaceous Subduction

Mesozoic plate convergence in SE Sundaland has been a source of debate for decades. A determination of plate convergence boundaries and timing have been explained in many publications, but not all boundaries were associated with magmatism. Through integration of both plate configurations and magmatic deposits, the basement can be accurately characterized over time and areal extents. This paper will discuss Cretaceous subductions and magmatic arc trends in SE Sundaland area with additional evidence found in JS-1 Ridge. At least three subduction trends are captured during the Mesozoic in the study area: 1) Early Jurassic – Early Cretaceous trend of Meratus, 2) Early Cretaceous trend of Bantimala and 3) Late Cretaceous trend in the southernmost study area. The Early Jurassic – Early Cretaceous subduction occurred along the South and East boundary of Sundaland (SW Borneo terrane) and passes through the Meratus area. The Early Cretaceous subduction occurred along South and East boundary of Sundaland (SW Borneo and Paternoster terranes) and pass through the Bantimala area. The Late Cretaceous subduction occurred along South and East boundary of Sundaland (SW Borneo, Paternoster and SE Java – South Sulawesi terranes), but is slightly shifted to the South approaching the Oligocene – Recent subduction zone. Magmatic arc trends can also be generally grouped into three periods, with each period corresponds to the subduction processes at the time. The first magmatic arc (Early Jurassic – Early Cretaceous) is present in core of SW Borneo terrane and partly produces the Schwaner Magmatism. The second Cretaceous magmatic arc (Early Cretaceous) trend is present in the SW Borneo terrane but is slightly shifted southeastward It is responsible for magmatism in North Java offshore, northern JS-1 Ridge and Meratus areas. The third magmatic arc trend is formed by Late Cretaceous volcanic rocks in Luk Ulo, the southern JS-1 Ridge and the eastern Makassar Strait areas. These all occur during the same time within the Cretaceous magmatic arc. Though a mélange rock sample has not been found in JS-1 Ridge area, there is evidence of an accretionary prism in the area as evidenced by the geometry observed on a new 3D seismic dataset. Based on the structural trend of Meratus (NNE-SSW) coupled with the regional plate boundary understanding, this suggests that both Meratus & JS-1 Ridge are part of the same suture zone between SW Borneo and Paternoster terranes. The gradual age transition observed in the JS-1 Ridge area suggests a southward shift of the magmatic arc during Early Cretaceous to Late Cretaceous times.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

Geochemistry and geochronology of OIB-type, Early Jurassic magmatism in the Zhangguangcai range, NE China, as a result of continental back-arc extension

2018 ◽  
Vol 158 (1) ◽  
pp. 143-157 ◽  
Author(s):  
Guangying Feng ◽  
Yildirim Dilek ◽  
Xiaolu Niu ◽  
Fei Liu ◽  
Jingsui Yang
Keyword(s):  
East Asia ◽  
Trace Element ◽  
Partial Melting ◽  
Early Jurassic ◽  
Ne China ◽  
Mafic Rocks ◽  
Asthenospheric Mantle ◽  
Trace Element Contents ◽  
Pacific Slab ◽  
Back Arc

AbstractThe Zhangguangcai Range in the Xing’an Mongolian Orogenic Belt, NE China, contains Early Jurassic (c. 188 Ma) Dabaizigou (DBZG) porphyritic dolerite. Compared with other island-arc mafic rocks, the DBZG dolerite is characterized by high trace-element contents, relatively weak Nb and Ta enrichments, and no Zr, Hf or Ti depletions, similar to OIB-type rocks. Analysed rocks have (87Sr/86Sr)i ratios of 0.7033–0.7044, relatively uniform positive ɛNd(t) values of 2.3–3.2 and positive ɛHf(t) values of 8.5–17.1. Trace-element and isotopic modelling indicates that the DBZG mafic rocks were generated by partial melting of asthenospheric mantle under garnet- to spinel-facies conditions. The occurrence of OIB-like mafic intrusion suggests significant upwelling of the asthenosphere in response to lithospheric attenuation caused by continental rifting. These processes occurred in an incipient continental back-arc environment in the upper plate of a palaeo-Pacific slab subducting W–NW beneath East Asia.

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