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Beijing, China

Li Z.,Zhejiang University | Chen H.,Zhejiang University | Song B.,Beijing Center | Li Y.,Zhejiang University | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2011

The temporal relations of different types of rocks in the Tarim large igneous province (TLIP) are studied using stratigraphic correlation, lithologically spatial distribution and isotopic ages. The TLIP covers an area >250,000km2 in the western and central part of the Tarim Basin. The lithological units of the TLIP include basalt, diabase, layered intrusive rock, breccia pipe mica-olivine pyroxenite, olivine pyroxenite, gabbro, ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke. This is the first report for the spatial distribution of the TLIP from the spatial section lines, which shows the stratigraphic correlation among basaltic lava, tuff, interlayered mudstone, siltstone and sandstone and the thicknesses of the basaltic lavas from different field sections and drill holes, and the basalts from the Kupukuziman and Kaipaizileike Formations were subdivided in the drill hole sections. This indicates that the basaltic lavas were widely distributed in the Tarim Basin. Combined with previous study of geochemical and Sr-Nd-Pb isotopic characterization from the basalts and their genetic link with mantle plume activity, and large diabase swarms developments, the Permian igneous units constitute a Tarim large igneous province. Zircon SHRIMP U-Pb dating firstly yields 284.3±2.8Ma for the quartz syenite porphyry. Recent SHRIMP and LA-ICP-MS zircon U-Pb and 40Ar/39Ar ages are used to discuss temporal relations of different rock units in the TLIP formed between 290 and 274Ma, and these data are more reliable than the K-Ar ages of 220-310Ma reported previously. The sequence of magmatism of the TLIP in the central and western parts of the Tarim Basin are basaltic lava in the Kupukuziman and Kaipaizileike Formations (285-290Ma), layered mafic-ultramafic rock, mica-olivine pyroxenite breccia pipe, diabase and ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke (274-284Ma). © 2011.

Du L.,Chinese Academy of Geological Sciences | Yang C.,Chinese Academy of Geological Sciences | Ren L.,Chinese Academy of Geological Sciences | Song H.,Chinese Academy of Geological Sciences | And 3 more authors.
Acta Petrologica Sinica | Year: 2012

Paleoproterozoic magmas are widely distributed in Ltiliang Mountains, and the petrogenesis and tectonic setting of these magmas are significant for reshaping the geological evolution of the North China Craton. In this paper, we report Dujiagou feldspar porphyrite, intermediate basic volcanic rocks from the Jinzhouyu Formation of the Ltiliang Group and Ehutan gneiss in Ltiliang Mountains. SHRIMP U-Pb zircon dating of two Dujiagou feldspar porphyrite samples yield the ages of 2189 ±6Ma and 2186 ± 3Ma, respectively, and one Ehutan dioritic gneiss sample gets a SHRIMP U-Pb zircon age of 2182 ±5Ma. Dujiagou feldspar porphyrites show the characteristics of A-type granite formed in a post orogenic setting. While, intermdiate basic volcanic rocks in the Jinzhouyu Formation and Ehutan gneisses have the characteristics of volcanic rocks formed in island arc setting. Considering the tectonic setting of 2. 2 ∼2. OGa magmatic events in the North China Craton, the formation of the 2. 2 ∼ 2. IGa magmatic rocks is probably related to its tectonic position during the Paleoproterozoic, with Ltiliang Mountains being located at the margin of the North China Craton. The 2. 2 ∼ 2. IGa magmatic rocks in the study area were formed in both island arc and rift regimes at about same time.

Gao L.-Z.,Chinese Academy of Geological Sciences | Wang Z.-Q.,Chinese Academy of Geological Sciences | Xu Z.-Q.,Chinese Academy of Geological Sciences | Yang J.-S.,Chinese Academy of Geological Sciences | Zhang W.,Beijing Center
Geological Bulletin of China | Year: 2010

Neoproterozoic glaciations of Quruqtagh area in Tarim basin are recognized, four of which appear to be global and with different volcanic rocks. In recent years, "Snow earth" hypothesis put forwards to the study of glaciation, any advancement of sedimentary, depositional environment and glaciation chronostratigraphic dating for the four glaciations in Quruqtagh area in Tarim basin, which will put more attention to global. This paper gives a new zircon SHRIMP U-Pb dating to be showing an evidence for the Neoproterozoic glaciations of Quruqtagh area in Tarim basin.

Castro N.A.,Federal University of Ceara | Ganade de Araujo C.E.,University of Sao Paulo | Basei M.A.S.,University of Sao Paulo | Osako L.S.,Federal University of Ceara | And 2 more authors.
Journal of South American Earth Sciences | Year: 2012

We present field relationships, major and trace element geochemistry and U-Pb SHRIMP and ID-TIMS geochronology of the A-type Ordovician Quintas pluton located in the Ceará Central Domain of the Borborema Province, in northeastern Brazil. This pluton presents a concentric geometry and is composed mainly of syenogranite, monzogranite, quartz syenite to quartz monzodiorite, monzogabbro and diorite. Its geochemical characteristics [SiO 2 (52-70%), Na 2O/K 2O (1.55-0.65), Fe 2O 3/MgO (2.2-7.3), metaluminous to sligthly alkaline affinity, post-collisional type in (Y + Nb) × Rb diagram, and A-type affinity (Ga > 22 ppm, Nb > 20 ppm, Zn > 60 ppm), REE fractioned pattern with negative Eu anomaly] are coherent with post-collisional A 2-type granitoids. However, the emplacement of this pluton is to some extent temporally associated with the deposition of the first strata of the Parnaíba intracratonic basin, attesting also to a purely anorogenic character (A 1-type granitoid). The emplacement of this pluton is preceded by one of the largest known orogenesis of the planet (Neoproterozoic Pan-African/Brasiliano) and, if it is classified as an A 2-type granitoid, it provides interesting constraints about how long can last A 2-type magmatic activity after a major collisional episode, arguably triggered by disturbance of the underlying mantle, a topic extensively debated in the geoscience community. © 2011 Elsevier Ltd.

Wan Y.,Chinese Academy of Geological Sciences | Wan Y.,Beijing Center | Liu D.,Chinese Academy of Geological Sciences | Liu D.,Beijing Center | And 10 more authors.
Precambrian Research | Year: 2011

The evolution of the North China Craton (NCC) is well known for a marked 2.55-2.50Ga tectonothermal event. However, supracrustal and intrusive rocks of 2.75-2.70Ga are in fact widely distributed in the western Shandong Province, the most important area of Archaean basement in the eastern part of the NCC. This paper reports SHRIMP U-Pb dating and LA-ICPMS Hf isotopic composition of zircons from 2.75-2.70Ga supracrustal and trondhjemite-tonalite-granodiorite (TTG) rocks in that area. Three fine-grained (hornblende) biotite gneiss samples (known locally as leptynite, with meta-volcanic or volcanosedimentary rock protoliths) and five TTG samples have SHRIMP zircon U-Pb ages varying from 2.75 to 2.70Ga and 2.74 to 2.71Ga, respectively. Zircons from most of the samples have high positive e{open}Hf(t) values (+4.7 to +10.0) and tDM(Hf) ages (2.85-2.60Ga) similar to their zircon U-Pb ages. This indicates that the rocks represent largely juvenile crustal additions derived from depleted mantle only a short time before. However, some granitoids show e{open}Hf(t) zircon values of -13.6 to +5.1 and tDM(Hf) of 3.51-2.80Ga. Therefore, the strong 2.75-2.70Ga tectonothermal event in the western Shandong Province involved not only juvenile addition to the continental crust but also intracrustal recycling of older components. Combined with craton-wide data, it is shown that the NCC is similar to many other cratons around the world where tectonothermal events of ∼2.7Ga are well developed. However, the main difference is that in the NCC, superimposed ∼2.5Ga tectonothermal events were much stronger than in most other cratons. © 2011 Elsevier B.V.

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