内蒙古准格尔黑岱沟超大型煤型镓矿床的形成与物质来源

鄂尔多斯盆地东北缘黑岱沟太原组顶部6号煤层属于低等煤化程度的低硫烟煤,其中铝土质粘土岩、煤层中超 常含有勃姆铝石,发现超常含镓、超常富集稀土,7段煤层平均含Ga 44.8 μg/g、含∑REE 110.82～467.21 μg/g,显示出铝、镓、稀土元素三者地球化学行为的相似性和共生特性.是特殊地质背景与古沉积环境下的产物.研究认为,铝、镓、稀土元素三者有共同的来源:①古老基底剥蚀区,古陆富钾高铝的岩浆岩与变质岩建造;②中奥陶统顶部风化剥蚀面产出的上石炭统本溪组粘土层及铝土层中富集的镓是重要来源;③煤层系中粘土质砾岩中发现显量火山晶屑及火山灰,部分提供易分解的铝-镓物源;④下二叠统太原组海陆交互滨海-溻湖相、三角洲相、堡岛与沼湖沉积岩相古地理优越,是煤层与铝土质粘土层发育集中富集含镓的良好沉积古环境.总之,镓的物源具有多来源、继承性、分时期、有阶段复杂富集的特点.     

安徽铜陵矿集区南部新生代岩浆活动——来自科学深钻TK01的证据

本文主要是对铜陵矿集区南部丁桥科学深钻中的碱性辉长岩进行了LA-MC-ICPMS锆石U-Pb定年,年龄为63.54±0.53 Ma,表明碱性辉长岩是新生代岩浆侵入活动的产物。全岩主、微量研究结果表明TK01中的碱性辉长岩富钾(K_2O平均为1.75%)、富碱(K_2O+Na_2O平均为3.90%)、富钛(TiO_2平均为1.58%),富集大离子不相容元素和轻稀土元素,亏损重稀土元素,属于过铝质岩石。SiO_2-K_2O图解中,样品点落在含钾较高的钾玄岩和钙碱性区域中,岩浆演化过程中有矿物的分离结晶作用。碱性辉长岩的锆石εHf(t)值介于-4.7~-11.5。推测TK01中的碱性辉长岩主要来源于富集地幔,稍有陆壳物质的混染,岩浆形成于大陆板内拉张的构造背景。     

Geochemistry,Sr–Nd–Pb–Hf isotopes systematics and geochronological constrains on petrogenesis of the Xishan A-type granite and associated W–Sn mineralization in Guangdong Province,South China

The Xishan deposit, located in the western Guangdong Province in South China, is a quartz-vein type W-Sn deposit with an average Sn grade of 0.1–0.4 wt%. The deposit is temporally and spatially associated with Xishan alkali feldspar granite. The W–Sn mineralization is present mainly as veins that are hosted by the granite. In this paper we present new zircon U–Pb age, whole-rock geochemical data, Sr–Nd–Pb–Hf isotopic data and Re–Os age in order to constrain the nature and timing of magmatism and mineralization in the Xishan mining district with implications on geodynamic settings. LA–ICP–MS zircon U–Pb analyses yielded an age of 79.14 ± 0.31 Ma for the alkali feldspar granite, consistent with the molybdenite Re–Os age of 79.41 ± 1.11 Ma. The alkali feldspar granite shows high contents of SiO₂ (71.52–76.25 wt%), high total alkalis (Na₂O + K₂O = 9.35–13.51 wt%), high field strength elements (e.g. Zr = 95.4–116 ppm, Y = 97.1–138 ppm, Nb = 36.1–55.5 ppm, Ga = 97.1–138 ppm), and rare earth elements (total REE = 171.8–194.0 ppm) as well as high Ga/Al ratios (10,000 × Ga/Al = 3.23–3.82) suggesting that it has the geochemical characteristics of A-type granite and shows an A₂ subtype affinity. Sr–Nd isotopes of the alkali feldspar granite show that (⁸⁷Sr/⁸⁶Sr)_i values range from 0.7111 to 0.7183, and the ε_Nd(t) values and Nd model ages (T_2DM) vary from −6.8 to −6.5 and 1414 to 1433 Ma, respectively. The Pb isotopic compositions are variable, with ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values ranging from 18.783 to 18.947, 15.709 to 15.722 and 38.969 to 39.244, respectively, indicating that the alkali feldspar granite was derived from a mantle-crust mixed source. In situ Hf isotopic analyses reveal that the alkali feldspar granite has ε_Hf(t) values ranging from −9.69 to −0.04 and two-stage Hf model ages from 1145 Ma to 1755 Ma, indicating that the alkali feldspar granite was formed by the partial melting of Mesoproterozoic crusts of the Cathaysia Block with additions of mantle-derived materials. These results, together with previously presented regional geological relationships, suggest that the formation of the Xishan granite and associated W–Sn mineralization is related to lithospheric extension and asthenospheric upwelling that are attributed to a directional change of Pacific plate motion.     

In–situ LA–ICP–MS trace elemental analyzes of magnetite: The Tieshan skarn Fe–Cu deposit,Eastern China

The Tieshan Fe–Cu deposit is located in the Edong district, which represents the westernmost and largest region within the Middle–Lower Yangtze River Metallogenic Belt (YRMB), Eastern China. Skarn Fe–Cu mineralization is spatially associated with the Tieshan pluton, which intruded carbonates of the Lower Triassic Daye Formation. Ore bodies are predominantly located along the contact between the diorite or quartz diorite and marbles/dolomitic marbles. This study investigates the mineral chemistry of magnetite in different skarn ore bodies. The contrasting composition of magnetite obtained are used to suggest different mechanisms of formation for magnetite in the western and eastern part of the Tieshan Fe–Cu deposit. A total of 178 grains of magnetite from four magnetite ore samples are analyzed by LA–ICP–MS, indicating a wide range of trace element contents, such as V (13.61–542.36 ppm), Cr (0.003–383.96 ppm), Co (11.12–187.55 ppm) and Ni (0.19–147.41 ppm), etc. The Ti/V ratio of magnetite from the Xiangbishan (western part of the Tieshan deposit) and Jianshan ore body (eastern part of the Tieshan deposit) ranges from 1.32 to 5.24, and 1.31 to 10.34, respectively, indicating a relatively reduced depositional environment in the Xiangbishan ore body. Incorporation of Ti and Al in magnetite are temperature dependent, which hence propose that the temperature of hydrothermal fluid from the Jianshan ore body (Al = 3747–9648 ppm, with 6381 ppm as an average; Ti = 381.7–952.0 ppm, with 628.2 ppm as an average) was higher than the Xiangbishan ore body (Al = 2011–11122 ppm, with 5997 ppm as an average, Ti = 302.5–734.8, with 530.8 ppm as an average), indicating a down–temperature precipitation trend from the Jianshan ore body to the Xiangbishan ore body. In addition, in the Ca + Al + Mn versus Ti + V diagram, magnetite is plotted in the skarn field, consideration with the ternary diagram of TiO₂–Al₂O₃–MgO, proposing that the magnetite ores are formed by replacement, instead of directly crystallized from iron oxide melts, which provide a better understanding regarding the composition of ore fluids and processes responsible for Fe mineralization in the Tieshan Fe–Cu deposit.     

Mass Fractions of Forty‐Six Major and Trace Elements,Including Rare Earth Elements,in Sediment and Soil Reference Materials Used in Environmental Studies

Development of new techniques, enabling simultaneous determination of large numbers of elements in environmental samples, can force analysts to use certified reference materials that do not contain all the elements of interest. In this paper, the mass fractions of forty‐six major and trace elements, including rare earth elements (REE), are presented in one soil (NCS DC 77302 also known as GBW 07410) and five sediment (Metranal‐1, IAEA 405, MESS‐3, NCS DC 73309 also known as GBW 07311 and NCS DC 75301 also known as GBW 07314) certified reference materials determined by high resolution inductively coupled plasma‐mass spectrometry. The selected certified materials represent a spectrum of geological matrices often analysed in environmental studies. Measured elements include certified elements, elements listed with information values as well as new elements absent from certificates, including REEs and some other elements. REE + Y mass fractions in the river sediment reference material Metranal‐1 are reported for the first time. The results obtained are in agreement with available certified or information values.     

“Spherulite-like” jadeite growth in shock-melt veins of the Novosibirsk H5/6 chondrite

The Novosibirsk H5/6 ordinary chondrite has signs of shock metamorphism, such as dark shock-melt veins (SMVs) crossing the chondrite host rock. The plagioclase composition grains (Ab₇₈An₁₄Or₇) with jadeite were found in the host-rock fragments inside the SMVs. Jadeite has an unusual radial-concentric spherulite-like microtexture. The spherulite-like jadeite formed from the molten plagioclase grain under high-pressure and high-temperature conditions during an impact event. The crystallization was accompanied by sodium-potassium differentiation between coexisting jadeite and residual melt. The PT-conditions of jadeite formation were estimated to be 3-14 GPa and 1400-2150 °C. Jadeite crystallization, Na-K differentiation, and the pressure-temperature estimates of jadeite formation in the Novosibirsk chondrite are very close to those in the Chelyabinsk LL5 chondrite. The spherulite-like microtexture and jadeite-glass coexistence, most likely, point to a high cooling rate of the SMVs at the pressure release stage of the metamorphic process.     

《中国数字地震台网观测报告》震级的确定

概述了用我国数字化地震台网的资料测定的各种震级标度及相关问题。同时阐明矩震级标度Mw的优势和良好的应用前景。建议今后我国观测报告中给出新参数Mw。     

氧同位素第6期北印度洋的一次重大古海洋学事件

北印度洋赤道海岭的远洋沉积记录在氧同位素第6期的早期,即167～160ka期间,揭示出一次重大的古海洋学事件。在多项代用指标中,浮游有孔虫组合和通量的变化对该事件的反映最为强烈,因此将其命名为“第6期海洋生态环境严重恶化事件”。该事件以广适性种Globigerinita glutinata的高度发育、凉水种Neogloboquadrina pachyderma和Globigerina bulloides的异常增多、其他有孔虫常见种的普遍减少及有孔虫总量的大幅度降低为特征。结合其他代用指标和邻区资料,认为导致事件发生的主控因素在于超强的南亚冬季风及其所引发的表层水温降低和贫瘠的深层水团上涌。一般情况下,南亚冬季风对研究区环境的影响力远较夏季风弱,它的阶段性超常强化似乎总与青藏高原的强烈隆升有关。可推测,发生在第6期的生境恶化事件很可能是最近一次高原大规模构造抬升的产物。     

锂辉石单矿物中锂含量ICP- MS和ICP- AES分析方法准确性对比研究

锂是我国重要的战略金属资源,锂辉石是伟晶岩型锂矿床中最重要的工业矿物之一。有效、合理圈定锂矿体、评价锂矿床的开发利用价值、深入研究锂矿成矿机制,锂元素含量的准确测定具有重要意义。本文以新疆维吾尔族自治区的卡鲁安、大红柳滩和镜儿泉锂矿床中锂辉石单矿物为研究对象,首次开展了伟晶岩型锂矿床中锂辉石单矿物锂元素ICP- MS和ICP- AES分析方法准确性对比研究。本文选取三个锂矿床共22件具有代表性的锂辉石单矿物样品,采用高压密闭湿法消解法,对ICP- MS和ICP- AES分析方法测定锂元素的工作条件(包括雾化气流速、辅助气流速、等离子体流速等)进行了详细探讨。测定结果表明,针对同一份锂辉石单矿物消解溶液,ICP- MS分析方法得到的锂元素存在系统性误差,较ICP- AES分析结果,结果偏差约28倍,锂元素含量损失近648%。同时进一步对ICP- MS测定锂元素结果的系统误差可能来源作了分析,提出目前技术条件下ICP- MS溶液分析方法用于测定锂辉石单矿物的锂元素含量尚不可取,宜采用操作简单、耐盐度高、无需内标校正的ICP- AES分析技术。     

论鄂尔多斯盆地陕北盐洼镇钾1井奥陶系马四段的重复

陕北奥陶纪盐洼区钻探的镇钾1井"马五6盐层段"(奥陶系马家沟组五段6分段)出现了异常的岩性组合序列,盐岩厚度大幅度减薄,代之以厚度100 m以上的纯碳酸盐岩地层,这一变化单从沉积学角度无法解释。为了弄清该井异常岩性段的层位归属,开展了岩性组合、测井旋回、碳氧同位素对比和地震剖面多种资料的综合分析。纵向地层岩性、测井旋回特征、碳氧同位素对比分析表明,这套地层是构造复杂化了的异常地层序列,并非原地沉积,厚度超过100 m的碳酸盐岩地层实为马四段(马家沟组四段),与下伏原地正常沉积的马四段重复。地震剖面显示马四段重复可能与塑性盐岩卷入复杂化了的逆断层有关。因此,镇钾1井钻前预测的"马五6盐层段"实际上是以马四段为主的逆冲断片,该井地层存在重复。镇钾1井马四段重复的确认,有助于正确认识陕北盐洼区马五6地层充填序列,推动局部构造—沉积相关研究工作的进一步开展。