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The Altun orogenic belt, located on the northern margin of the Tibetan Plateau, records the assembly and breakup of the Rodinia supercontinent. In this paper, we report the petrography, zircon U–Pb ages and Hf isotope data, and bulk geochemistry of the Hongliugou alkali feldspar granites from the Altun orogenic belt to constrain their petrogenesis and tectonic implication. Zircon U–Pb dating yielded ages of 857–851 Ma, interpreted as the emplacement ages of the granites. The granites are metaluminous; have high SiO2, K2O, and rare‐earth element (REE) contents; low CaO and P2O5 contents; high FeOt/MgO ratios; and high 10,000 × Ga/Al values. They show marked depletion in heavy REEs, enrichment in light REEs, and pronounced negative Eu anomalies. These rocks are enriched in high‐field‐strength elements, depleted in Ba, Sr, P, and Ti, and lack Nb and Ta anomalies. These petrological and geochemical characteristics are consistent with those of A‐type granites. The samples plot in the A1‐type field in a discrimination diagram for A‐type granites. Zircon εHf(t) values vary from +1.76 to +7.40 with two‐stage Hf model ages of 1.27 to 1.63 Ga, implying that the granites were derived mainly from juvenile crust. On the basis of these and previous results, we propose that the Hongliugou alkali feldspar granites formed in an intraplate rift setting related to the initial breakup of Rodinia. [ABSTRACT FROM AUTHOR]

Abstract: The South Altyn continental block is an important geological unit of the Altyn Tagh orogenic belt, in which numerous Neoproterozoic granitoids crop out. Granitoids are mainly located in the Paxialayidang–Yaganbuyang area and can provide indispensable information on the dynamics of Rodinia supercontinent aggregation during the Neoproterozoic. Therefore, the study of granitoids can help us understand the formation and evolutionary history of the Altyn Tagh orogenic belt. In this work, we investigated the Yaganbuyang granitic pluton through petrography, geochemistry, zircon U–Pb chronology, and Hf isotope approaches. We obtained the following conclusions: (1) Yaganbuyang granitoids mainly consist of two‐mica granite and granodiorite. Geochemical data suggested that these granitoids are peraluminous calc–alkaline or high‐K calc–alkaline granite types. Zircon U–Pb data yielded ages of 939±7.1 Ma for granodiorite and ∼954 Ma for granitoids, respectively. (2) The εHf(t) values of two–mica granite and granodiorite are in the range of –3.93 to +5.30 and –8.64 to +5.19, respectively. The Hf model ages (TDM2) of two‐mica granite and granodiorite range from 1.59–.05 Ga and 1.62–2.35 Ga, respectively, indicating that the parental magma of these materials is derived from ancient crust with a portion of juvenile crust. (3) Granitoids formed in a collisional orogen setting, which may be a response to Rodinia supercontinent convergence during the Neoproterozoic. [ABSTRACT FROM AUTHOR]

Quantitative analyses of the spatial distribution of fault structures can provide a theoretical basis for forecasting prospective ore deposits. Characteristics and complexity of fault structure distribution in the Qitianling area, Southern Hunan Province, China, were quantitatively calculated and appraised by fractal and multifractal methods to evaluate the relation between fault structures and ore-prospecting potential. The results show that the lengths of faults can be modeled as multifractals. Multifractal spectra evidently reflect the characteristics of the scaling of fault structures. The box-counting dimension value (D) of fault structures is equal to 1.656, as indicates complexity of the spatial distribution of faults and favorable structural conditions for the formation of ore deposits. Moreover, the D values of sub-regions were calculated and isopleths of their fractal dimension values were plotted accordingly. Overlay analyses of isopleths of fractal dimension values and distributions of known ore deposits show that areas with the larger fractal dimension values of fault structures have more ore deposits. This spatial coupling relationship between D values and ore deposits can be used to forecast and explore other ore deposits. On the basis of complexity theory for ore-forming systems, three exploration targets with high D values were delineated as prospective ore deposits. [ABSTRACT FROM AUTHOR]

The Banshanping granitoid rocks distribute in the east of the North Qinling orogenic belt. It is a diorite-quartz diorite-granodiorite-granite series, spreading in a NW-SE direction, and intrudes into the Erlangping Group. The SiO2 content ranges from 57.04% to 76.56%, Na2O from 2.05% to 4.65%, K2O from 0.84% to 3.40%. Major element characteristics indicate that Banshanping granitoid rocks have properties of I type granotoids. SREE ranges from 36.51 ppm to 473.25 ppm, and LREE/HREE ratios lie between 3.95 and 22.18. Negative Eu anomalies are not obvious in most samples, though there are obvious Nb, P and Ti positive anomalies. The zircon LA-ICP-MS ages of Banshangping granitoid rocks are 496.0±8.1 Ma-486.9±9.3 Ma. Hf isotope shows that 176Hf/177Hf ratios range from 0.282721 to 0.282876, εHf( t) values from 8.5 to 14, all positive, and corresponding modal ages (TDM2) range from 559 Ma to 908 Ma. Based on Hf isotope characteristics and existing Sm-Nd and Rb-Sr isotope data, we consider that the Banshanping granitoid rocks originate from mantle-derived material, i.e. the igneous rocks that formed in Neoproterozoic, and there may be a certain amount of crust-derived material during the formation of Banshanping granitoid rocks. [ABSTRACT FROM AUTHOR]

The Boziguoer A-type granitoids in Baicheng County, Xinjiang, belong to the northern margin of the Tarim platform as well as the neighboring EW-oriented alkaline intrusive rocks. The rocks comprise an aegirine or arfvedsonite quartz alkali feldspar syenite, an aegirine or arfvedsonite alkali feldspar granite, and a biotite alkali feldspar syenite. The major rock-forming minerals are albite, K-feldspar, quartz, arfvedsonite, aegirine, and siderophyllite. The accessory minerals are mainly zircon, pyrochlore, thorite, fluorite, monazite, bastnaesite, xenotime, and astrophyllite. The chemical composition of the alkaline granitoids show that SiO2 varies from 64.55% to 72.29% with a mean value of 67.32%, Na2O+K2O is high (9.85%-11.87%) with a mean of 11.14%, K2O is 2.39%-5.47% (mean = 4.73%), the K2O/Na2O ratios are 0.31-0.96, Al2O3 ranges from 12.58% to 15.44%, and total FeOT is between 2.35% and 5.65%. CaO, MgO, MnO, and TiO2 are low. The REE content is high and the total SREE is (263-1219) ppm (mean = 776 ppm), showing LREE enrichment and HREE depletion with strong negative Eu anomalies. In addition, the chondrite-normalized REE patterns of the alkaline granitoids belong to the 'seagull' pattern of the right-type. The Zr content is (113-1246) ppm (mean = 594 ppm), Zr+Nb+Ce+Y is between (478-2203) ppm with a mean of 1362 ppm. Furthermore, the alkaline granitoids have high HFSE (Ga, Nb, Ta, Zr, and Hf) content and low LILE (Ba, K, and Sr) content. The Nb/Ta ratio varies from 7.23 to 32.59 (mean = 16.59) and the Zr/Hf ratio is 16.69-58.04 (mean = 36.80). The zircons are depleted in LREE and enriched in HREE. The chondrite-normalized REE patterns of the zircons are of the 'seagull' pattern of the left-inclined type with strong negative Eu anomaly and without a Ce anomaly. The Boziguoer A-type granitoids share similar features with A1-type granites. The average temperature of the granitic magma was estimated at 832-839°C. The Boziguoer A-type granitoids show crust-mantle mixing and may have formed in an anorogenic intraplate tectonic setting under high-temperature, anhydrous, and low oxygen fugacity conditions. [ABSTRACT FROM AUTHOR]

The article present the research that the Dunhuang Block, Western China represents a Paleozoic orogenic belt. Topic include the zircons were imaged using cathodoluminescence (CL) at the Chinese Academy of Geological Sciences to examine internal structures; and the Yulinhe granodiorite is an I-type granite, and the residual rock is mainly amphibolite facies, comprising amphibole and plagioclase, which may have links with the coeval amphibolite in the Dunhuang Block.