Development of the Asian Tethyan Realm

International Journal of Earth Sciences -     

Carboniferous rifted arcs leading to an archipelago of multiple arcs in the Beishan–Tianshan orogenic collages (NW China)

International Journal of Earth Sciences - The Beishan and East Tianshan Orogenic Collages in the southernmost Central Asian Orogenic Belt (CAOB) record the final stages of evolution of the...     

Geological Characteristics and Metallogenic Setting of Representative Magmatic Cu‐Ni Deposits in the Tianshan‐Xingmeng Orogenic Belt,Central Asia

A great number of magmatic Cu-Ni deposits(including Kalatongke in Xinjiang and Hongqiling in Jilin) are distributed over a distance of almost 3000 km across the Tianshan-Xingmeng Orogenic Belt, from Tianshan Mountains in Xinjiang in the west, to Jilin in eastern China in the east. These deposits were formed during a range of magmatic episodes from the Devonian to the Triassic. Significant magmatic Cu-Ni-Co-PGE deposits were formed from the Devonian period in the Nalati arc(e.g. Jingbulake Cu-Ni in Xinjiang), Carboniferous period in the Puerjin-Ertai arc(e.g. Kalatongke Cu-Ni-Co-PGE in Xinjiang), Carboniferous period in the Dananhu-Touquan arc(e.g. Huangshandong, Xiangshan and Tulaergen in estern Tianshan, Xinjiang) to Triassic period in the Hulan arc(e.g. Hongqiling Cu-Ni in Jilin). In addition to the overall tectonic, geologic and distribution of magmatic Cu-Ni deposits in the Tianshan-Xingmeng Orogenic Belt, the metallogenic setting, deposit geology and mineralization characteristics of each deposit mentioned above are summarized in this paper. Geochronologic data of Cu-Ni deposits indicate that, from west to east, the metallogenic ages in the Tianshan-Xingmeng Orogenic Belt changed with time, namely, from the Late Caledonian(～440 Ma), through the Late Hercynian(300–265 Ma) to the Late Indosinian(225–200 Ma). Such variation could reflect a gradual scissor type closure of the paleo Asian ocean between the Siberia Craton and the North China Craton from west to east.     

从前陆褶皱冲断带看大地构造相分析及其意义

以浙西北为例,基于上二叠统长兴组(P₂c)和大隆组(P₂d)以及下三叠统政棠组(T₁z)深水浊积岩的发现,初步认为该区古生代至早三叠世具被动大陆边缘沉积楔特征。综合大地构造分析进一步表明研究区构造样式总体上以向北西逆冲的冲褶席(duplex)为特征,构造变形强度和密度自南东向北西呈递减趋势。自南东向北西具明显的分带性。该区大地构造相主要为前陆褶皱冲断带相,而上三叠统乌灶组(T₃w)为前陆磨拉石盆地相,二者可能是该区始于早中生代(T₁—T₃)造山作用的响应。大地构造相分析不仅较为圆满地解释了研究区的众多地质现象,为造山带模式提供新的制约,而且能为研究区提出新的战略目标。     

Silurian Seismites in Hanxia, Yumen, North Qilian Mountains, and Their Tectonic Significance

The Caledonian erogenic belt of the North Qilian Mountains is an intensely active structure belt. In the process of the Late Caledonian syn-orogeny, the North Qilian-Hexi Corridor area was situated on the tectonic background of a syn-orogenic basin. In response to the orogenic process of the North Qilian Mountains, typical earthquake event deposits-seismites of the Silurian were widely distributed around Hanxia of Yumen City, the Liyuan River of Sunan County and Biandukou of Minle County. In the Hanxia area, where seismites are typically developed, clastic deposits of tidal-flat facies are the background deposits of the Hanxia Formation. The earthquake event deposits are characterized by sandy mudstone veins, synsedimentary microfractures, micro-corrugated laminations and earthquake breccias, which in turn constitute complex seismites, featuring seismic corrugation, shattering and liquefied sandy mudstone veins, auto-clastic breccias and intraclastic parabreccias. The seismites and tidal flat deposits f     

新疆西昆仑库地复理石源区性质及构造背景分析

出露于库地北一些克沟中的复理石作为西昆仑库地蛇绿岩的基本组成单元之一，其本身具有重要的大地构造位置，但长期以来，有关其形成的构造环境分析却尚属空间。笔者等在对该套复理石沉积序列详细分析的基础上，本文从沉积大地构造学的角度，利用岩石矿物，主量元素，微量元素及稀土元素等地球化学数据对其母源区性质及构造背景进行了一系列分析判别，确定其形成的构造环境为大洋岛弧的弧前盆地。     

Discovery and Genetic Mechanism of Basic Granulite in the Altay Orogenic Belt, Xinjiang, NW China

Altay granulite (AG), which represents the product of high-grade metamorphism in the lower crust, was newly found in the Wuqiagou area, Fuyun County in the Altay orogenic belt, Northwest China. It is composed mainly of hypersthene, augite, basic plagioclase, amphibole and brown biotite. Its mineral compositions of amphibole and biotite are rich in Mg/(Mg+Fe2+) and Ti. Geochemically, the AG is enriched in Mg/(Mg+Fe2+) and A12O3, and poor in CaO, with depletion of U, Th, K and Rb contents. Furthermore, geochemical data reflect that the protolith of the AG is igneous-genetic calc-alkaline basalt formed under an island arc environment. The AG has ZREE of 92.38-96.58 ppm and enriched LREE model with weak positive Eu anomaly of 1.09-1.15. In the MORB normalized spider diagram, the AG shows tri-doming pattern with a strong negative Nb anomaly and medium negative P and Ti anomalies, reflecting that the AG has tectonic relation with subduction or subduction-related materials. The P-T conditions of peak metamorphi     

The adakite connection of the Tuwu–Yandong copper porphyry belt, eastern Tianshan, NW China: trace element and Sr-Nd-Pb isotope geochemistry

The Tuwu–Yandong porphyry copper belt lies in the eastern Tianshan mountains, eastern section of the Central Asian orogenic belt. The copper mineralization is mainly hosted in plagiogranite porphyries intruded into early Carboniferous volcanic rocks of the Paleozoic Dananhu island arc between the Tarim and Siberian plates. The plagiogranite porphyries have contents of 65–73 wt% SiO₂, 14–17 wt% Al₂O₃, 0.9–2.2 wt% MgO, 3–16 ppm Y, 0.4–1.40 ppm Yb, 347–920 ppm Sr, and positive Eu anomalies. The rocks also exhibit positive ɛ _Nd(t) values (+5.0 to +9.4) and low initial ⁸⁷Sr/⁸⁶Sr values (0.70316–0.70378). Such features are similar to those of adakites derived from partial melting of a subduction-related oceanic slab. The mineralization age is early Carboniferous (350–320 Ma), which is close to that of the porphyries. The close relationship between the Cu mineralization and the porphyry is also indicated by their similar Sr-Nd-Pb isotopic compositions. We suggest that the copper porphyry (magma) system in the Dananhu island arc was formed by direct melting of an obliquely subducting early Carboniferous oceanic slab.     

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