东昆仑哈日扎铅锌多金属矿床金属矿物与S-Pb同位素特征

东昆仑哈日扎铅锌多金属矿床位于东昆仑造山带东段,紧邻昆中断裂北侧。已获得的资料显示哈日扎铅锌多金属矿床具有良好的找矿前景。通过对矿床内主要金属矿物及其S Pb同位素组成进行详细研究,探讨其成矿温度与物质来源。研究表明：闪锌矿中Fe元素含量为9751%~12736%,Zn/Cd比值的变化范围为5650~11439,初步推测成矿温度为中—低温;矿床中各硫化物的δ34S值变化范围为-38‰~-05‰,具有深部岩浆硫的特征,且不同硫化物矿物中的S同位素未达到平衡分馏;Pb同位素变化相对较小,206Pb/204Pb、207Pb/204Pb及208Pb/204Pb值变化范围分别为18254~18504、15614~15800和38429~39028;表明其成矿物质主要来源于下地壳的部分熔融与深部岩浆的混合。     

Genesis of the Ore-related Granite Porphyry and Molybdenite Re-Os Age of Laomiaogou Porphyry-skarn Mo Deposit,Western Henan Province: Implications for Regional MineralizationEI北大核心CSCD

The newly discovered Laomiaogou porphyry-skarn Mo deposit is located south of the Machaoying fault in western Henan province. The ore-body is hosted in the contact between the Laomiaogou granite porphyry dyke and the Duguan Formation. LA-ICP-MS U-Pb analyses for zircons from the granite porphyry yield a weighted mean 206Pb/238U age of 152.1±0.6 Ma, and seven molybdenite separates yield a weighted mean age of 151.9±0.9 Ma and isochron age of 151.6±5.1 Ma. Thus, the granite porphyry dyke and Mo mineralization are contemporaneous. The ore-related granite porphyry dyke is a peraluminous I-type granite with high contents of SiO2 and K2O. The rocks are strongly depleted in P, Nb, Ta and Ti, indicative of intensive fractionation of apatite and Fe-Ti oxides, and characterized by low whole-rock εNd(t) (-20.6 to -17.6) and zircon εHf(t) values (-26.9 to -22.6). The old tDM2(Nd) ages (2.37 to 2.61 Ga) and zircon tDM2(Hf) ages (2.62 to 2.88 Ga) suggest that the granite porphyry was likely derived from an ancient crustal source. Considering the tectonic evolution and geochemical characteristics of the granite as well as other Mesozoic granites in the southern margin of the North China Craton, we suggest that the Laomiaogou granite porphyry dyke and Mo were most likely derived from partial melting of the Taihua Group metamorphic rocks under extensional tectonic regime related to the subduction of the paleo-pacific plate. © 2018, Science Press. All right reserved.     

新疆东昆仑卡尔瓦西地区马尔争组牙形石的发现及地质意义

通过分析新疆东昆仑卡尔瓦西地区马尔争组中上段地层,揭示该套地层的沉积旋回及韵律特征。沉积标志和微量元素分析表明,该区马尔争组地层为浅海至半深海碳酸盐台地相沉积。对研究区马尔争组采集的牙形石标本进行研究和分析,10件样品中采集到2枚Neogondolella regale化石标本,该牙形石广泛分布于早三叠世斯派斯特期末期—中三叠世安尼期早期。因此,该区原定为二叠系马尔争组的形成时代可能是早中三叠世。     

东昆仑西段夏日哈木榴辉岩原岩属性及陆(弧)陆碰撞

东昆仑西段夏日哈木榴辉岩呈透镜状分布于古元古代金水口群中,榴辉岩的SiO_2含量47.4%~50.78%,Mg#值为40~62,表明其原岩为分异程度较高的基性岩,属于拉斑玄武岩系列。基于岩石Nb的含量,将夏日哈木榴辉岩分为两类——富Nb型榴辉岩(Nb7×10~(-6))和正常榴辉岩(Nb7×10~(-6))。富Nb型榴辉岩具有贫SiO_2、MgO、Al_2O_3,富集FeOt、TiO_2的特点;稀土元素配分曲线具有右倾的OIB特点,与古生代富Nb玄武岩和Seki玄武岩微量元素特征类似;微量元素具有弱的Nb、Ta、Ti的负异常,与古生代富Nb玄武岩特征类似。正常榴辉岩具有贫FeOt、TiO_2,富集SiO_2、MgO、Al_2O_3的特点;稀土元素配分曲线具有弱右倾的E-MORB特点,微量元素具有弱的Nb、Ta、P的负异常,U、Sr的正异常,类似于Okinawa板内弧后盆地玄武岩微量元素特征。富Nb型榴辉岩的εNd(0)和εNd(t=571Ma)值分别为0~4.55、-0.88~7.26,正常榴辉岩的εNd(0)和εNd(t=571Ma)值分别为2.2~5.19、3.17~6.22,两者均位于加里东HP-UHP变质带和大别-苏鲁HP-UHP变质带榴辉岩Sm-Nd同位素组成范围内。在微量元素图解上,样品显示具有地壳混染的趋势。由此可知,夏日哈木榴辉岩的原岩可能是具有陆内弧后盆地玄武岩性质的岩石,源区受到俯冲板片熔体的改造,岩浆过程中同化混染一定量的下地壳。根据现有的年代学资料,夏日哈木榴辉岩峰期变质可能发生在晚奥陶世—志留纪。夏日哈木榴辉岩可能是在弧后盆地消亡过程中,弧陆发生俯冲碰撞的结果。     

Geochronology and geochemistry of Early Devonian intrusions in the Qimantagh area,Northwest China: evidence for post-collisional slab break-off

The Qimantagh area of Northwest China lies in the western part of the East Kunlun Orogenic Belt and is characterized by extensive magmatism, particularly in the Triassic. However, recent research has shown that Devonian magmatism was also widespread in this area and has a genetic relationship with mineralization. This article presents a detailed study of three types of Early Devonian intrusions: high-K calc-alkaline granites, A-type granites, and mafic intrusions, all from the Qimantagh region. These rocks were subjected to precise zircon U–Pb dating, major and trace element analyses, and Sr–Nd isotope measurements, focusing on the Lalingzaohuo (eastern Qimantagh) and Yemaquan (central Qimantagh) monzogranites, as well as the coeval Tanbeixuefeng (western Qimantagh) mafic dike swarm. To better understand the Early Devonian igneous activity in the Eastern Kunlun, data for other coeval granitoids were compared with our data. The Yemaquan monzogranite yielded a mean zircon U–Pb age of 400.5 ± 1.4 Ma. These rocks are metaluminous to slightly peraluminous, with Al₂O₃ contents of 13.10–14.16 wt.%, high alkali contents (total K₂O + Na₂O) of 6.89–7.68 wt.%, relatively low Sr contents (79–192 ppm), and high (La/Yb)_N ratios, all of which indicate an I-type granite affinity. The Lalingzaohuo monzogranites yielded mean zircon U–Pb ages of 396.2–402.2 Ma. These rocks have higher SiO₂ and alkali contents than the Yemaquan monzogranite, with high 10,000 Ga/Al ratios, high Zr + Nb + Ce + Y contents, high Fe₂O₃^T/MgO ratios, and high Y contents, indicating an A-type granite affinity. These two monzogranites have initial ⁸⁷Sr/⁸⁶Sr ratios of 0.703–0.706 and εNd(t) values of –0.1 to –0.7. The Sr–Nd isotopic data require a significant input of a mantle component in the petrogenesis of these granites. The Tanbeixuefeng diabase dikes formed at ~396 Ma and have a continental tholeiitic affinity, as evident from small Ti–Nb–Ta anomalies and high contents of light rare earth and large-ion lithophile elements. We propose that post-collisional slab break-off was responsible for the generation of these Early Devonian intrusions in the Qimantagh area.     

新疆阿克陶县苏巴什一带磁铁矿地质特征及成因浅析

新疆阿克陶县苏巴什一带具有优越的成矿地质条件,带内相继发现了多个铁矿床,并具有一定的空间连续性。本文通过总结对比带内不同铁矿床的地质特征、赋矿地层、构造变质变形等特征,并以带内典型的磁铁矿床为例,深入分析矿体地质特征、矿体形态、矿物组合及矿石结构构造特征,认为该地区的磁铁矿具有相似的矿床成因及成矿演化史,经历了原始沉积期、区域变质改造期和热液叠加改造期3个阶段,属于沉积变质型磁铁矿。通过物探磁测,明确了区内磁异常主要由磁铁矿（化）引起,并总结了带内磁铁矿找矿标志,为该区铁矿进一步勘探调查指明方向。     

西昆仑北缘沙拉吾如克铜铅矿地质特征及矿床成因浅析

西昆仑北缘沙拉吾如克铜铅矿是区域内较为典型的矿床类型之一,矿体主要赋存于加里东期阿勒玛勒克杂岩体中,受沙拉吾如克断裂的控制。矿石矿物主要有黄铜矿、方铅矿、黄铁矿等,矿石铜铅品位相对较贫,一般Cu含量为0.50%~1.33%(平均0.7%),Pb为0.60%~5.99%(平均0.9%)。铜铅矿石的稀土总量(ΣREE)为83.5×10~(-6)~122×10~(-6),相对围岩(ΣREE为257×10~(-6)~342×10~(-6))来说,明显偏低。铜铅矿石的δEu为0.90~1.04,δCe为0.95~0.96,表现为铕和铈的无异常。含矿岩系稀土元素含量及配分模式显示出成矿元素直接来源于阿勒玛勒克杂岩体,特别是来自晚序次的似斑状石英二长岩或二长花岗岩(均为埃达克岩),矿床类型属于斑岩型矿床,为区域上加里东期成矿事件的产物,与大同一带加里东期铜钼矿的形成具有一致的大陆动力地质学过程,即原特提斯洋(西昆仑北洋)向南俯冲消减,进而引起花岗质岩浆活动并成矿。     

Early Ordovician CA-IDTIMS U–Pb zircon dating and conodont biostratigraphy,Canning Basin,Western Australia

A continuously cored section of more than 300 m through the Nambeet Formation and the basal part of the conformably overlying Willara Formation in the Olympic 1 petroleum well, drilled in the Canning Basin of northern Western Australia, yields valuable information that increases by more than 40% the number of precise isotopic ages available to constrain the Ordovician Period. New CA-IDTIMS U–Pb zircon ages for seven bentonite layers in the Olympic 1 core are integrated into a new conodont biostratigraphic framework for the Early Ordovician comprising four biozones recognised in this well. The weighted mean U–Pb dates range from 479.37 ± 0.16 Ma within the late Tremadocian Paroistodus proteus conodont Biozone, to 470.18 ± 0.13 Ma near the boundary between the Floian and Dapingian stages within the Jumudontus gananda conodont Biozone. The intervening Prioniodus oepiki–Serratognathus bilobatus conodont Biozone (early Floian) and succeeding Oepikodus communis conodont Biozone (middle Floian) are similarly well constrained by isotopic dates centred on ca 477 Ma for the early Floian and by three ages of 473–471 Ma for the middle Floian. The seven new isotopic dates significantly increase the precision of dating for the Early Ordovician, where previously only two ages with limited or imprecise biostratigraphic control were known globally.     

The start‐up of the Dolomia Principale/Hauptdolomit carbonate platform (Upper Triassic) in the eastern Southern Alps

Wide carbonate platform environments developed on the western passive margin of the Tethys during the Late Triassic, after a major climate change (Carnian Pluvial Episode) that produced a crisis of high‐relief microbial carbonate platforms. The peritidal succession of this epicontinental platform (Dolomia Principale/Hauptdolomit, Dachstein Limestone) is widespread in the Mediterranean region. However, the start‐up stage is not fully understood. The original platform to basin depositional geometries of the system have been studied in the north‐eastern Southern Alps, close to the Italian/Slovenian boundary where they are exceptionally preserved. Sedimentological features have been investigated in detail by measuring several stratigraphic sections cropping out along an ideal depositional profile. The analysis of the facies architecture allowed reconstruction of the palaeoenvironments of the Dolomia Principale platform during its start‐up and early growth stages in the late Carnian. The carbonate platform was characterized by an outer platform area, connected northward to steep slopes facing a relatively deep basin. Southward, the outer platform was connected to inner sheltered environments by a narrow, often emerged shelf crest. Behind this zone, carbonate sedimentation occurred in shallow lagoons and tidal flats, passing inward to a siliciclastic mudflat. The Dolomia Principale platform was initially aggrading and able to keep pace with a concomitant sea‐level rise, and then prograding during the late Carnian. This stratigraphic interval was correlated with the Tuvalian succession of the Dolomites, allowing depiction of the depositional system on a wide scale of hundreds of kilometres. This large‐scale depositional system presents features in common with some Palaeozoic and Mesozoic carbonate build‐ups (for example, the Permian Capitan Reef complex, Anisian Latemar platform), both in terms of architecture and prevailing carbonate producers. A microbial‐dominated carbonate factory is found in the outer platform and upper slope. The recovery of high‐relief microbial carbonate platforms marks the end of the Carnian Pluvial Episode in the Tuvalian of Tethys.     

Calpionellid zones of the Tithonian–Berriasian exotic limestone clasts from the Outer Carpathians,Poland

Calpionellids and chitinoidellids were identified from exotic limestone clasts occurring in flysch deposits of the Early Cretaceous to Oligocene age from the Silesian and Subsilesian nappes of the Polish Outer Carpathians. They represent the remnants of carbonate sedimentation along the northern and southern margin of the Severin-Moldavidic Basin, areas which are no longer preserved on the surface. Chitinoidellid and calpionellid assemblages characterize the Chitinoidella, Crassicollaria and Calpionella zones (latest early Tithonian–early Berriasian). The calpionellid zonation for the Western Carpathians was used for the present study, but some difficulties were encountered resulting from the application of this zonation. Cathodoluminescence imaging (CL) was useful for the identification of these microfossils in samples containing sparse and poorly preserved specimens, especially in the studied shallow-water limestone (the so-called Štramberk-type limestones).