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对赣南上犹县侵入于陡水加里东期花岗岩的煌斑岩的地球化学进行了分析, 并重点分析了其中锆石的U-Pb年龄和Hf同位素组成. 岩石学和地球化学特征显示陡水煌斑岩属于高钾弱碱性辉云煌斑岩, 高Mg # (0.74), Ni (253 mg/g), Cr (893 mg/g), 但又富REE, Rb, Sr, Ba和K等不相容元素表明其母岩浆可能起源于被非壳源介质交代过的富集地幔. 形貌学和LAM-ICPMS U-Pb定年显示煌斑岩中的锆石都是捕获的, 大多数形成于古元古代晚期1.86 Ga, 少量形成于显生宙的不同时期. 古元古代锆石具有岩浆成因特征并具有相似的 176 Hf/ 177 Hf和 176 Lu/ 177 Hf同位素比值, 表明它们来源于同一火成岩基底. 该基底年龄和Hf同位素组成相似于浙南龙泉地区古元古代花岗岩, 而不同于南岭地区的基底组成, 说明研究区属于东华夏武夷地块的古元古代基底向西延伸的一部分. 这些古元古代锆石具有低的Hf同位素组成, 显示壳源特征. Hf模式年龄, 以及老的继承核的存在和结合前人的资料, 表明古元古代岩浆活动的源岩是新太古代地壳, 暗示武夷地块存在更老的基底. 古元古代克拉通化后, 武夷地块一直稳定达1.0 Ga以上. 5颗显生宙锆石的U-Pb年龄和Hf组成表明研究区深部的古元古代基底在加里东期、印支期和燕山早期受到了多期岩浆活动的改造, 而且在加里东时期的岩浆活动还可能伴有新生地壳的再造.

Based on scanning electronic microscopic observation of three fault rocks in ductile-brittle shearing-sliding zones (including one palimpsest mylonite sampled from deep bore cores of Cajon Pass, California, two flowing-structured carbargillites sampled from Shaancan Well 1 located in north Shaanxi, and Well NH located in Huanghai, respectively), micron- and nanometer-scaled ultra-fine grinding grain texture of fault rocks is discovered in this study. And the geological significance of grinding grain texture is discussed in terms of its particulate organization, rheology of particulate slipping, laminar petrography and micro dynamics including dynamotherman metamorphism, fluid transferring, particulate autorotation, and so on. In addition, the remaining problems to be solved and broad prospects in this new study field are also discussed. ∗Supported by Natural Science Foundation of China (Grant Nos. 40372092, 40373024, 40172067, and 40172034) and the State Key Laboratory of Geology and Exploitation...

to cite the paper EPISODES Volume: 30 Issue: 3 Pages: 162-186 Published: September, 2007; International audience; Chinese East Tianshan is a key area for understanding the Paleozoic accretion of the southern Central Asian Orogenic Belt. A first accretion-collision stage, before the Visean, developed the Eo-Tianshan range, which exhibits north-verging structures. The geodynamic evolution included: i) Ordovician-Early Devonian southward subduction of a Central Tianshan ocean beneath a Central Tianshan arc; ii) Devonian oceanic closure and collision between Central Tianshan arc and Yili-North Tianshan block, along the Central Tianshan Suture Zone; iii) Late Devonian-earliest Carboniferous closure of a South Tianshan back-arc basin, and subsequent Central Tianshan-Tarim active margin collision along the South Tianshan Suture Zone. A second stage involved: i) Late Devonian-Carboniferous southward subduction of North Tianshan ocean beneath the Eo-Tianshan active margin (Yili-North Tianshan arc); ii) Late Carboniferous-Early Permian North Tianshan-Junggar collision. The Harlike range, unit of Mongolian Fold Belt, collided with Junggar at Mid- Carboniferous, ending a north-dipping subduction. The last CAOB oceanic suture is likely the North Tianshan Suture Zone, between Yili-North Tianshan and Junggar. During the Permian, all the already welded units suffered from a major wrenching, dextral in Tianshan, sinistral in Mongolian Fold Belt, due to opposite motion of Siberia and Tarim.

The Yili Block is important for understanding the Late Paleozoic geodynamic evolution of Central Asia. It is bounded to the north by the Northern Tianshan Carboniferous flysch and ophiolitic mélange. The center of the Block is dominated by Carboniferous sedimentary rocks with intercalation of volcanic rocks. Petrological and geochemical features of these Carboniferous volcanic rocks show that: (1) they belong to the calc-alkaline series, (2) they display prominent Nb-Ta negative anomalies consistent with subduction-related magmas, and (3) HFSE-based discriminations place these volcanic rocks in the field of continental arcs. The depositional evolution of the sedimentary series shows evidence for Carboniferous sedimentation in a basin instead of rifting as previously proposed. All these evidences, together with the occurrence of contemporaneous turbidites and ophiolitic mélange along the northern boundary of the Yili Block, allow us to infer that the northern border of the Yili Block was a continental active margin during the Carboniferous. The Late Carboniferous southward subduction that finally closed the Late Devonian to Early Carboniferous North Tianshan oceanic basin was followed by Permian-Mesozoic polyphase transcurrent faulting.

In the last few decades, the Late Paleozoic–Early Mesozoic tectonic evolution of South China has been quite controversial. The focus of debate is on both the age of ophiolites and the Late Paleozoic–Early Mesozoic geological and geodynamic environment. The Huaiyu Domain is located in the NE part of South China and exposes numerous significant geological features that are keys to understand the tectonics of South China. In this paper, we present some new evidence on stratigraphy, petrology and SHRIMP zircon U-Pb geochronology, and together with other geological and geochemical data available in the literature, and the following conclusions are suggested: 1) The eastern Jiangnan ophiolites belt, dated at 858±11 Ma by SHRIMP zircon U-Pb method, was generated during the Neoproterozoic, but not the Late Paleozoic; 2) The sedimentary rocks associated with these oceanic rocks do not contain radiolarian but Neoproterozoic acritarchs; 3) During Permian–Early Triassic times, the Huaiyu Domain was dominantly characterized by a shallow sea depositional environment since deep sea sediments are absent; and 4) The pre-Devonian tectonics of South China has been reworked by late polyphase tectonism through the Triassic and the Cretaceous periods. A Late Paleozoic–Early Mesozoic deep marine domain floored by oceanic crust never existed in the study area. The geochronological and structural data do not comply with a Late Paleozoic– Early Mesozoic South China Ocean.

La chaîne du Tianshan s'étend sur plus de 3000 km en Asie centrale, elle sépare le Tarim au Sud du Juggar et du Kazakhstan au Nord (Fig. 1a). La collision indienne est responsable du haut-relief actuel, mais l'architecture de la chaîne est due à plusieurs événements d'âge Paléozoïque. Classiquement, la chaîne du Tianshan est divisée en Tianshan Nord, Tianshan Central, Tianshan Sud et Bloc de Yili (Fig. 1b). Ce dernier est souvent considéré comme l'extension occidentale du Tianshan Central, mais nos données structurales, géochimiques et paléomagnétiques suggèrent que ces domaines et leurs limites doivent être redéfinis.

In Xinjiang Province of NW China, the Tianshan Belt belongs to the Late Paleozoic Variscan orogens that shaped up the Eurasian continent. Most of geologists drew to a conclusion that the Tianshan Belt was built during Paleozoic times through oceanic subduction, accretion and collision between the main Precambrian cratons such as Tarim, Junggar and Kazakhstan and some intervening microcontinents such as the Yili Block. However, there are still some controversies on the geodynamics of Paleozoic Tianshan, especially the West Tianshan (WTS), which was less studied than the East Tianshan. In particular, the tectonic significance in terms of heat transfer and crustal rheology of the huge magmatic rocks that develop in WTS is rarely taken into account in the lithosphere-scale evolution models.

International audience; The Chinese Tianshan Belt is one of the key regions for the understanding of tectonics of the Central Asian Orogenic Belt (CAOB). An international field excursion and workshop were organized to conduct a common observation and discussion on the tectonic evolution of the Chinese Tianshan. This report summarizes the main achievements, including acknowledged geological features, controversial and remaining scientific problems, and discussion of a tentative geodynamic model. Thus, it is helpful to clarify what has been done in the past, what should be improved and what needs to be done in the future and therefore to better understand the tectonics of the Chinese Tianshan Belt and the CAOB as well.