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The Triassic tectonic evolution and affinity among the Yangtze Block, Qinling Orogenic Belt and Songpan-Ganzi Terrane remain subjects of ongoing scientific debate. In this context, the sedimentary rocks of Xujiahe Formation (second segment) (T3x2) represent an ideal case for addressing this issue. In this study, new stratigraphic, geochemical and detrital zircon analyses have been conducted on two sections of the T3x2. The stratigraphic assemblage and features suggests a braided delta as the depositional setting. Whole-rock geochemical results indicate that the sandstones from the T3x2 exhibit moderate palaeo-weathering and primarily originate from upper crustal felsic rocks, mostly S-type granites. The detrital zircons within these sandstones display distinctive age peaks at intervals of 200-300 Ma, 700-900 Ma, and 1800-2000 Ma, similar to those from the Qinling Orogenic Belt. Both the clastic particle composition and whole-rock geochemistry indicates that the T3x2 sections were deposited in a tectonic environment transitioning from a passive to an active continental margin, highlighted by a braided delta influenced by rivers flowing from the northeast to the southwest. [ABSTRACT FROM AUTHOR]

This study presents a new data set that contains zircon U--Pb ages, whole-rock geochemistry, and Hf isotopes of the Huhetaoergai granitic pluton in the northern Ya-Gan Fault zone, northern Alxa, China. The Huhetaoergai pluton is composed of medium- to coarse-grained biotite monzogranite and coarse-grained biotite monzogranite with K-feldspar megacrysts, with U-Pb zircon ages of 220.5 [+ or -] 1.9 Ma and 226.5 [+ or -] 2.4 Ma, respectively. Granitoids are I-type granites with high [[epsilon].sub.Hf](t) values (9-11.05). These features indicate that the granitoids were generated from partial melting of juvenile crust and experienced an obvious fractional crystallization process. We speculate that the granitoids of the Huhetaoergai pluton were formed in an intraplate extensional environment during the post-collision process, indicating a crustal stretching and thinning event in the northern Ya-Gan Fault zone. Key words: Huhetaoergai pluton, I-type granites, geochemistry, zircon U--Pb dating, Hf isotopes. Un nouvel ensemble de donnees est presente qui contient des ages U-Pb sur zircons, des donnees geochimiques sur roche totale et les concentrations d'isotopes de Hf du pluton granitique de Huhetaoergai dans la partie nord de la zone de faille de Ya-Gan (Alxa septentrional, Chine). Le pluton de Huhetaoergai est compose de monzogranite a biotite a grains moyens a grossiers et de monzogranite a biotite a grains grossiers contenant des megacristaux de feldspath potassique qui donnent des ages U--Pb sur zircons de 220,5 [+ or -] 1,9 Ma et 226,5 [+ or -] 2,4 Ma, respectivement. Les granitoides sont de type I avec des valeurs de [[epsilon].sub.Hf](t) elevees (9-11,05). Ces caracteristiques indiquent qu'ils ont ete produits par la fusion partielle de croute juvenile et ont subi on processus de cristallisation fractionnee evident. Nous proposons que les granitoides du pluton de Huhetaoergai se sont formes dans un milieu d'extension intraplaque durant le processus post-collision, temoignant d'un episode d'etirement et d'amincissement de la croute dans la partie nord de la zone de faille de Ya-Gan. [Traduit par la Redaction] Mots-cles: pluton de Huhetaoergai, granites de type I, geochimie, datation U--Pb sur zircons, isotopes de Hf., Introduction The Central Asia Orogenic Belt, also known as the 'Central Asian mobile belt,' 'Central Asian Fold belt', or 'Altaids', is situated at the suture zone of the European, Siberian, [...]

The Jinchuan deposit, which is located in the Longshoushan uplift (LU) on the southwest margin of the Alxa Block (AB), is the third largest Ni‐Cu deposit in the world. There are igneous rocks in the LU that widely developed in ~830 Ma, which include ore‐bearing ultramafic rock and ore‐poor mafic‐ultramafic rocks. These rocks were produced in an intracontinental extension‐rift environment, which is likely related to the Rodinia supercontinent (RS) breakup. However, contemporary magmatic rocks are absent in the AB, except the ~830 Ma igneous rocks in the LU. In this study, we present two types of metamorphic mafic‐ultramafic rocks at the border of Jinchuan II and IV mineral areas, which is inside the F17 fault zone. One type is a red‐coloured altered rock formed by ultramafic rock oxidation; there are a small number of zircons with multiple ages in the rock, which are considered to be inherited and metamorphic (hydrothermal) zircons. The other type is a chlorite tremolite schist formed by the metamorphism of fault clastics; there are a large number of zircons developed in this rock, which are mostly magmatic zircons with ages between 900 and 800 Ma and a few hydrothermal zircons. Analysis of the trace elements, the 900–800 Ma zircons, have high (Sm/La)N, low Ce/Ce*, and high Th/U values, which fit the characteristics of typical magmatic zircons. There are also high Y, U, HREE, Nb, and Ta values, which indicates that the host rocks were mostly larvikite and dolerite, and high Y, Ce, Yb, Th, Gd, and Er values indicate a within‐plate basaltic origin. All these 900–800 Ma zircons have a εHf (t) in the range of −2 to −7, which is similar to the Jinchuan ore‐bearing ultramafic rock with a partial melting origin of enriched mantle. The absence of detrital zircon age peaks in the Neoproterozoic indicates that the AB has been separated from the North China Craton since the Neoproterozoic to Paleozoic. The detrital zircons in the Yangtze Block (YB) strata with Neoproterozoic ages are slightly younger than those in the AB, with more depleted εHf (t) values, which is similar to the zircons from the Jiangnan Orogen igneous rocks. All this evidence indicates that the AB may have experienced at least 100 Myr of intracontinental extension‐rift environment from 900 to 800 Ma during the Neoproterozoic and participated in the breakup of the RS. However, the location of the AB during the Rodinia may not have been beside the YB. [ABSTRACT FROM AUTHOR]

The Zaozigou gold deposit lies south of the Xiahe—Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes. Diorite porphyry, quartz diorite porphyry and biotite diorite porphyry are mineral‐bearing dikes, whereas granite porphyry is unrelated to gold mineralization. To compare the relationship between different dikes and mineralization, this study analyzed the cathodoluminescence (CL) of zircon crystals in all four types of dikes exposed in the Zaozigou deposit, using a zircon typological classification. The formation temperature of the granite porphyry (734°C) was higher than the average temperature of the other three types of dikes (704°C), whereas the former's alkalinity index (395) was lower than the average alkalinity index of the other three dikes (425). The ΣREE amount of granite porphyry (147.18 ppm) was smaller than the average ΣREE amount of the other three dikes (246.80 ppm) and its δEu value (0.33) was larger than the average δEu values of the other three dikes (0.30). The U‐Pb ages of zircon in the four types of dikes were relatively consistent with the crystallization ages of approximately 240 Ma, which indicates that all four types of dikes intruded in the Middle Triassic. Compared to the other three ore‐bearing dikes, the morphology of the zircon crystals in the barren dikes evolved from S13 to S5 and then returned to S13. These results indicate that the barren dike underwent an increase in temperature and a decrease in alkalinity, which may be an important reason for the absence of mineralization. [ABSTRACT FROM AUTHOR]