scholarly journals Geochronology of Magmatism and Mineralization in the Dongbulage Mo-Polymetallic Deposit, Northeast China: Implications for the Timing of Mineralization and Ore Genesis

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 255 ◽  
Author(s):  
Wang ◽  
Li ◽  
Liu ◽  
Jiang ◽  
Chen
Keyword(s):  
Northeast China ◽  
Late Jurassic ◽  
Genetic Relationships ◽  
Molar Ratio ◽  
Time Interval ◽  
Bulk Rock ◽  
Calc Alkaline ◽  
Porphyritic Granite ◽  
Polymetallic Deposit ◽  
High K

The recently discovered Dongbulage Mo-polymetallic deposit is located in the southern part of the Great Xing’an Range, northeast China. Mineralization is closely related to the emplacement of Middle–Late Jurassic granitoids. In order to understand the petrogenetic link between mineralization and host granitoids, this study presents new zircon U–Pb ages, bulk-rock geochemistry, and molybdenite Re–Os ages for the Dongbulage deposits. LA-ICP-MS zircon U–Pb dating of the monzogranite and syenogranite intrusions yielded two weighted mean 206Pb/238U ages: of 164 ± 2 Ma and 165 ± 3 Ma, respectively. The subvolcanic rocks (red porphyritic granite and rhyolite) yielded a time interval between 161 ± 2 and 162 ± 3 Ma. In addition, molybdenite from the Dongbulage deposit gave a Re–Os isochron age of 162.6 ± 1.5 Ma, which was interpreted as the age of the mineralization. The new geochronology has established the close temporal and genetic relationships between the mineralization event and the emplacement of the Middle–Late Jurassic granitoids. Bulk-rock geochemistry shows that the Dongbulage granitoids are characterized by high SiO2, K2O, and A/CNK [Al2O3/(CaO + Na2O + K2O)(molar ratio)] values, and low TiO2, CaO, and MgO values, indicating a metaluminous to peraluminous, high-K calc-alkaline affinity. The granitoids also featured enrichments of large ion lithophile elements and light rare earth elements (LREE), and a relative depletion of high field strength elements (HFSE), along with an increasing negative δEu anomaly. The high differentiation index (DI), ranging from 81.75 to 94.76, and obvious fractionation between LREE and HREE, indicate that the Dongbulage granitoids are highly fractionated, metaluminous–peraluminous, and high-K calc-alkaline I-type granites. Combined with the regional geology, the Dongbulage granitoids may have formed during post-orogenic extension that followed the Mongol–Okhotsk Ocean closure coeval with subduction of the paleo-Pacific plate.

Release of Uranium from Uraninite in Granites Through Alteration: Implications for the Source of Granite-Related Uranium Ores

2021 ◽  
Author(s):  
Long Zhang ◽  
Zhenyu Chen ◽  
Fangyue Wang ◽  
Noel C. White ◽  
Taofa Zhou
Keyword(s):  
Uranium Concentration ◽  
Geochemical Data ◽  
Uranium Deposits ◽  
Bulk Rock ◽  
Calc Alkaline ◽  
Alkaline Granite ◽  
Compositional Evolution ◽  
High K ◽  
Backscattered Electron ◽  
Uranium Sources

Abstract Uraninite is the main contributor to the bulk-rock uranium concentration in many U-rich granites and is the most important uranium source for granite-related uranium deposits. However, detailed textural and compositional evolution of magmatic uraninite in granites during alteration and associated uranium mobilization have not been well documented. In this study, textures and geochemistry of uraninites from the Zhuguangshan batholith (South China) were investigated by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The geochemical data indicate that the Longhuashan and Youdong plutons are peraluminous leucogranite, the Changjiang pluton is highly fractionated high-K calc-alkaline granite, and the Jiufeng pluton belongs to a high-K calc-alkaline association. Uraninites from the Longhuashan and Youdong granites have lower concentrations of ThO2 (0.9–4.0 wt %) and rare earth elements (REE)2O3 (0.1–1.0 wt %) than those from the Changjiang and Jiufeng granites (ThO2 = 4.4–7.6 wt %, REE2O3 = 0.7–5.1 wt %). Uraninites observed in the Longhuashan, Youdong, Changjiang, and Jiufeng granites yielded chemical ages of 223 ± 3, 222 ± 2, 157 ± 1, and 161 ± 2 Ma, respectively. The samples (including altered and unaltered) collected from the Longhuashan, Youdong, and Changjiang granites are characterized by highly variable whole-rock U concentrations of 6.9 to 44.7 ppm and Th/U ratios of 0.9 to 7.0, consistent with crystallization of uraninite in these granites being followed by uranium leaching during alteration. Alteration of uraninite, indicated by altered domains developing microcracks and appearing darker in backscattered electron (BSE) images compared to unaltered domains, results in the incorporation of Si and Ca and mobilization of U. In contrast, the least altered samples of the unmineralized Jiufeng granite have low U concentrations (5.3–16.4 ppm) and high ΣREE/U (13.6–49.4) and Th/U ratios (2.1–5.6), which inhibit crystallization of uraninite, as its crystallization occurs when the U concentration is high enough to exceed the substitution capacity of other U-bearing minerals. These results indicate that the Longhuashan, Youdong, and Changjiang granites were favorable uranium sources for the formation of uranium deposits in this area. This study highlights the potential of uraninite alteration and geochemistry to assist in deciphering uranium sources and enrichment processes of granite-related uranium deposits.

Geology, geochemistry, and geochronology of the Laozuoshan gold deposit, Heilongjiang Province, Northeast China: implications for multiple gold mineralization events and geodynamic setting

2018 ◽  
Vol 55 (6) ◽  
pp. 604-619 ◽  
Author(s):  
Meng Wu ◽  
Liang Li ◽  
Jing-gui Sun ◽  
Rui Yang
Keyword(s):  
Gold Deposit ◽  
Contact Zone ◽  
Northeast China ◽  
Gold Mineralization ◽  
Geodynamic Setting ◽  
Heilongjiang Province ◽  
Late Permian ◽  
Calc Alkaline ◽  
High K ◽  
Diorite Porphyry

The Laozuoshan gold deposit, located in the central part of the Jiamusi Massif, is hosted by the contact zone between granitic complex and Proterzoic strata. In this study, we present the results of geochronology and geochemistry of ore-related granodiorite and diorite porphyry, and hydrothermal sericite 40Ar/39Ar dating. The granodiorite and diorite porphyry in the Laozuoshan gold deposit are calc-alkaline and high-K (calc-alkaline) series, which are enriched in LREE and LILE and depleted in HFSE, with no depletion of Eu. The geochronology data show that zircon U–Pb ages of the granodiorite and diorite porphyry are ∼262 Ma and ∼105 Ma, respectively. The sericite 40Ar/39Ar ages are ∼194 Ma and ∼108 Ma. On the basis of previous researches, ore geology and geochronology studies show that the Laozuoshan gold deposit underwent at least two gold mineralization events. We suggest that the first one, which was related to skarnization, resulted from the collision between the Jiamusi and Songnen Massifs in Late Permian. The subsequent gold mineralization resulted from the subduction of the paleo-Pacific Plate in Early Cretaceous.

Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

2017 ◽  
Vol 34 (1) ◽  
pp. 45 ◽  
Author(s):  
Elizard González-Becuar ◽  
Efrén Pérez-Segura ◽  
Ricardo Vega-Granillo ◽  
Luigi Solari ◽  
Carlos Manuel González-León ◽  
...  
Keyword(s):  
Metamorphic Core Complex ◽  
Primitive Mantle ◽  
Isotopic Ratios ◽  
Magmatic Evolution ◽  
Calc Alkaline ◽  
Core Complex ◽  
High K ◽  
Sierra Madre ◽  
Plutonic Rocks ◽  
Metamorphic Core

Plutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous two-mica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitive-mantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40Ar/39Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Electron microscope and microprobe analysis of chlorite–mica stacks in the Wenlock turbidites, mid Wales, U.K.

1986 ◽  
Vol 123 (3) ◽  
pp. 299-306 ◽  
Author(s):  
Andrew J. Dimberline
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Source Area ◽  
Pressure Solution ◽  
Pore Waters ◽  
Bulk Rock ◽  
High K ◽  
Backscattered Electron

AbstractChlorite–mica stacks in the Wenlock turbidites have been studied using backscattered electron microscopy and electron microprobe analysis, combined with thin-section work and bulk rock chemical analysis. The stacks occur in fine sandstones and silt–mud turbidites and range in length from < 30 μm to 1.5 mm. They consist of interlayered packets of Fe-rich chlorite and mica.Combined textural and chemical data suggest that many of the stacks represent altered detrital biotite micas. A four-stage alteration sequence is proposed:(1) Subaerial alteration of biotite, in the source area, to interlayered biotite–hydrobiotite/vermiculite.(2) Post-depositional collapse of vermiculite to form a mica phase under conditions of high K+/H+ in the sediment pore waters.(3) Decrease in K+/H+ ratio, possibly due to H+ build up in the fermentation zone, causing alteration of biotite layers to chlorite.(4) Kinking of the stacks and pressure solution of chlorite early in the development of cleavage.

Sign in / Sign up

Export Citation Format

Share Document