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Yu-Jie Hao Yun-Sheng Ren Ming-Xin Duan Xuan Zhao Qun Yang Kuang-Yin Tong Chao Li 《Arabian Journal of Geosciences》2016,9(15):655
The Zhengguang deposit, a representative large gold deposit in the Duobaoshan ore field in NE China, is located in the northeast of the Central Asian Orogenic Belt (CAOB). Ore body emplacement was structurally controlled and occurs mainly at the contact zone between the strata of Duobaoshan Formation and an Ordovician diorite stock. The diorite rocks have a close genetic relationship with Au mineralization. Re–Os isotope dating of Au-bearing pyrite yields an isochron age of 506 ± 44 Ma (MSWD = 15). Based on present and previous dating results, it can be concluded that the Zhengguang deposit formed at ~480 Ma. The mineralization time of the Zhengguang deposit is nearly identical to those of the Duobaoshan and Tongshan deposits, indicating they are all derived from the same metallogenic system. The Duobaoshan-style porphyry Cu–Mo mineralization may exist at deeper levels at Zhengguang. The geochemical characteristics of the Zhengguang dioritic rocks presented in this paper are similar to those of bajaitic high-Mg andesite, and the magmas originated from a mantle wedge metasomatized by melts from a subducting oceanic slab at an active continental margin setting. The Ordovician magmatic–metallogenic events in the Duobaoshan ore field were caused by the westward subduction of an oceanic slab located between the Xing’an and Songliao blocks. It is worth pointing out that the Zhengguang deposit is the oldest known Phanerozoic Au deposit in NE China. Further studies of this deposit will improve understanding of the regularity of ore formation and aid mineralization forecast across the Duobaoshan region. 相似文献
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Peixin Duan Cui Liu Xuanxue Mo Jinfu Deng Jinhua Qin Yu Zhang Shipan Tian 《地学前缘(英文版)》2018,9(5):1417-1431
The Chalukou porphyry Mo deposit, located in the Great Hinggan Range, is the largest Mo deposit in northeast China, although the age and genesis of the associated magmatic intrusions remain debated.Here we report zircon U-Pb ages and trace elements, whole rock geochemistry and Sre Nd isotope data with a view to understand the relationship between the magmatism and molybdenum mineralization.Zircon U-Pb analysis yield an age of 475 Ma for rhyolite in the older strata, 168 Ma for the premineralization monzogranite, and 154 Ma for the syn-mineralization granite porphyry. The granite porphyry and quartz porphyry are considered as the ore-forming intrusions. These rocks are peraluminous, alkali-calcic, and belong to high-K to shoshonitic series with a strong depletion of Eu. They also display characteristics of I-type granites. The rocks exhibit wide variations of(87 Sr/86 Sr)iin the range of 0.705426 -0.707363, and ε_(Nd)(t) of -3.7 to 0.93. Zircon REE distribution patterns show characteristics between crust and the mantle, implying magma genesis through crust-mantle interaction. The Fe_2O_3/FeO values(average 1) for the whole rock and EuN/Eu*Nvalues(average 0.45), Ce~(4+)/Ce~(3+) values(average 301)for zircon grains from the granite porphyry are higher than those from other lithologies. These features suggest that the ore-forming intrusions(syn-mineralization porphyry) had higher oxygen fugacity conditions than those of the pre-mineralization and post-mineralization rocks. The Chalukou Mo deposit formed in relation to the southward subduction of the Mongol-Okhotsk Ocean. Our study suggests that the subduction-related setting, crust-mantle interaction, and the large-scale magmatic intrusion were favorable factors to generate the super-large Mo deposits in this area. 相似文献
45.
Huangling Gu Zhangxing Nie Jianghong Deng Liuan Duan Qing Hu 《International Geology Review》2018,60(11-14):1404-1434
ABSTRACTThe Guichi ore-cluster district in the Lower Yangtze River Metallogenic Belt hosts extensive Cu–Au–Mo polymetallic deposits including the Tongshan Cu–Mo, Paodaoling Au, Matou Cu–Mo, Anzishan Cu–Mo, Guilinzheng Mo and Zhaceqiao Au deposits, mostly associated with the late Mesozoic magmatic rocks, which has been drawn to attention of study and exploration. However, the metallogenic relationship between magmatic rocks and the Cu–Au-polymetallic deposits is not well constrained. In this study, we report new zircon U–Pb ages, Hf isotopic, and geochemical data for the ore-bearing intrusions of Guichi region. LA-ICP-MS U–Pb ages for the Anzishan quartz diorite porphyrite is 143.9 ± 1.0 Ma. Integrated with previous geochronological data, these late Mesozoic magmatic rocks can be subdivided into two stages of magmatic activities. The first stage (150–132 Ma) is characterized by high-K calc-alkaline intrusions closely associated with Cu–Au polymetallic ore deposits. Whereas, the second stage (130–125 Ma) produced granites and syenites and is mainly characterized by shoshonite series that are related to Mo–Cu mineralization. The first stage of magmatic rocks is considered to be formed by partial melting of subducted Palaeo-Pacific Plate, assimilated with Yangtze lower crust and remelting Meso-Neoproterozoic crust/sediments. The second stage of magmatism is originated from partial melting of Mesoproterozoic-Neoproterozoic crust, mixed with juvenile crustal materials. The depression cross to the uplift zone of the Jiangnan Ancient Continent forms a gradual transition relation, and the hydrothermal mineralization composite with two stages have certain characteristics along the regional fault (Gaotan Fault). Guichi region results from two episodes of magmatism probably related to tectonic transition from subduction of Palaeo-Pacific Plate to back-arc extensional setting between 150 and 125 Ma, which lead to the Mesozoic large-scale polymetallic mineralization events in southeast China. 相似文献
46.
Atmospheric circulation anomaly is a direct cause of weather and climate change. In the past, most researches for the relationship between Weather Type (WT) and precipitation have mainly focused on the subjective classification and diagnosis. Compared to the subjective analysis, objective classification uses more consistent index and standard unification, thus, we can get more WTs, and it has been widely used in many areas. By using daily 12UTC Sea Level Pressure (SLP), Precipitable Water (PW), and 700 hPa wind speed (UV700) data from ECMWF’s Interim Reanalysis, the classification of WTs over China was performed with the method of obliquely rotated T-mode principle component analysis. WT and its link to precipitation over China were further analyzed. The results show that the influence of different WTs on precipitation is not uniform over China, and also show distinctly difference in different seasons. A common feature is that WTs great impact on the regions and months with large precipitation, while less impact on regions and months have with less precipitation. In addition, precipitation trends originating from WT intensity changes are much more deterministic, significant, and predictable than trends from WT frequency changes. 相似文献
47.
Yong Chen Jing Duan Junling An Huizhi Liu Ulrich G?rsdorf Franz H.Berger 《大气和海洋科学快报》2021,14(5):24-29
卫星估雨精度的不确定性受到当地降雨类型和像元内降雨非均匀性影响,而结合这两个关键因素开展半干旱草原卫星估雨的研究有限.2009年夏,我们在中国锡林郭勒半干旱草原用多部微雨雷达和雨量计构建了9 km卫星像元降雨观测网,观测了像元内降雨非均匀性(空间变异系数CV),并评估了卫星估雨精度.结果表明:(1)CV值受像元内平均降雨量,降雨类型,降雨云面积及移向等影响,如高Cv值的降雨过程大多为平均降雨量小,对流性降雨过程,降雨云边缘像元CV值较高;(2)TRMM 3B42V7卫星估雨产品适用性较好,CMORPH和PERSIANN次之,但TRMM 3B42V7易在半干旱草原湖泊处高估降雨. 相似文献
48.
大兴安岭北部漠河盆地内广泛发育二十二站组,其形成时代及物质来源一直以来备受争议.本文在野外地质调查及岩相学的基础上,利用碎屑锆石LA-ICP-MS U-Pb法测年,并结合岩石地球化学等方法,探讨了二十二站组形成时代、物源区大地构造环境及沉积物来源.测年结果显示132个测点年龄主要分布在4个群落,分别为508.3~492.3 Ma;486.9~435.5 Ma;278.3~254.2 Ma;209.5~178.1 Ma.本次获得二十二站组最小碎屑锆石年龄为178.1 Ma,并结合漠河盆地东西部碎屑锆石的年龄,综合认为二十二站组形成时代应为中晚侏罗世.地球化学分析结果显示,二十二站组砂岩的稀土元素与活动大陆边缘的稀土元素曲线吻合较好,且相对亏损高场强元素(Nb和Ta)和大离子亲石元素(Ba和Sr),相对富集高场强元素(La、Th、Zr、Hf),地球化学特征与活动大陆边缘相似.综合古流向、源区母岩分析、碎屑锆石测年分析、微量元素特征等诸多因素,本次研究认为本区二十二站组砂岩的母岩主要来源于盆地南缘广泛分布的前中生代沉积-变质基底(兴华渡口岩群、佳疙瘩组、额尔古纳河组等)及各期中酸性火成岩. 相似文献
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Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models 下载免费PDF全文
The problem of predicting the geometric structure of induced fractures is highly complex and significant in the fracturing stimulation of rock reservoirs. In the traditional continuous fracturing models, the mechanical properties of reservoir rock are input as macroscopic quantities. These models neglect the microcracks and discontinuous characteristics of rock, which are important factors influencing the geometric structure of the induced fractures. In this paper, we simulate supercritical CO2 fracturing based on the bonded particle model to investigate the effect of original natural microcracks on the induced‐fracture network distribution. The microcracks are simulated explicitly as broken bonds that form and coalesce into macroscopic fractures in the supercritical CO2 fracturing process. A calculation method for the distribution uniformity index (DUI) is proposed. The influence of the total number and DUI of initial microcracks on the mechanical properties of the rock sample is studied. The DUI of the induced fractures of supercritical CO2 fracturing and hydraulic fracturing for different DUIs of initial microcracks are compared, holding other conditions constant. The sensitivity of the DUI of the induced fractures to that of initial natural microcracks under different horizontal stress ratios is also probed. The numerical results indicate that the distribution of induced fractures of supercritical CO2 fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small. 相似文献