不同植被覆盖率地区遥感矿化蚀变提取研究

从遥感图像上识别出的围岩蚀变信息往往是一种弱信息。地表植被和第四系覆盖的干扰,增加了遥感蚀变信息提取的难度。为了研究不同植被覆盖条件下的矿化蚀变信息提取方法,分别选取内蒙古西部戈壁荒漠基岩裸露区（温根地区）、中北部中覆盖草原区（达来庙地区）和东北部高覆盖森林草原区（颇格鲁山地区）,利用TM数据进行遥感蚀变信息提取方法研究,得出以下结论：在基岩裸露地区,利用比值法、主成分分析法均能较好地提取出矿化蚀变信息;在中覆盖草原区,利用掩膜对图像进行预处理,再利用主成分分析法提取矿化信息效果比较好;在高覆盖森林草原区,利用掩膜技术和抑制植被信息方法对遥感数据进行综合处理,再利用比值-主成分分析方法能够提取部分矿化蚀变信息。这些方法对今后在类似地区开展遥感蚀变信息提取工作具有一定的指导意义。     

对铬铁磨球组织选择的理论探讨

通过对磨球运动、受力状况和磨损机制及其影响因素的分析，提出了对磨球使用性能的要求；应用材料科学基本理论，重点探讨了铝铁磨球组织选择的方法、原则和依据。结论是：根据磨球的工况条件，准确判断磨球的磨损机制是合理选择磨球组织的前提。     

西藏尼雄矿田滚纠铁矿成矿作用机制：来自矿物学和稳定同位素证据

本文分析了冈底斯成矿带西段尼雄矿田滚纠铁矿石榴子石、辉石、绿泥石成因矿物学特征,结果显示矿区石榴子石多为钙铁榴石,并存在一定量的钙铝榴石;辉石主要为透辉石、次透辉石和铁次透辉石,表明成矿流体早期为酸性、高温和高氧逸度环境。矽卡岩内接触带富钙铝榴石,外接触带富钙铁榴石,反映成矿流体由矽卡岩内接触带运移至矽卡岩外接触带过程中,温度逐渐降低,而pH和氧逸度逐渐升高。绿泥石主要为富铁贫镁的铁镁绿泥石,其在低温(206~268℃)、低pH值、还原环境下形成。方解石C-O同位素揭示成矿流体δ¹³C_∑C为-2.6‰~-0.7‰,δ¹⁸O_V-SMOW为+9.8‰~+12.0‰。石榴子石、磁铁矿、石英δD_V-SMOW值为-121‰~-105‰,成矿流体δ¹⁸O_H2O为8.7‰~11.3‰,反映成矿流体主要来源于花岗质岩浆。磁铁矿矿石中黄铁矿弱富铁亏硫,S/Fe为1.05~1.07,Co/Ni>1,指示为岩浆热液成因;黄铁矿δ³⁴S为4.2‰~11.1‰,与花岗质岩浆硫相当,综合反映成矿物质也来源于花岗质岩浆。结合前人研究资料,认为高温、高氧逸度使金属元素大量进入岩浆,岩浆上升侵位、分异出富含成矿物质的流体。成矿流体运移过程中遭遇围岩,并与之反应形成矽卡岩和退化蚀变矿物,导致成矿流体物理化学性质改变,在温度(180~400℃)、氧化-弱氧化和弱碱性-碱性条件下,发生磁铁矿沉淀。     

安徽省庐江县泥河铁矿床地质特征及成因分析

泥河铁硫矿床位于长江中下游成矿带内庐枞盆地的西北部,矿床中铁、硫储量均达到大型矿床规模,硬石膏储量达到中型规模,是长江中下游成矿带内近年来重大找矿突破之一,其发现具有重要的理论意义和勘探价值.泥河矿区内主要地层为砖桥组和双庙组安山质火山熔岩和碎屑岩,侵入岩体主要为辉石闪长玢岩.磁铁矿体呈厚大的透镜状分布于闪长玢岩穹窿顶...     

Constraints on the mineralization processes of the Makeng iron deposit,eastern China: Fluid inclusion,H–O isotope and magnetite trace element analysis

The Makeng iron deposit is located in the Yong’an-Meizhou depression belt in Fujian Province, eastern China. Both skarn alteration and iron mineralization are mainly hosted within middle Carboniferous-lower Permian limestone. Five paragenetic stages of skarn formation and ore deposition have been recognized: Stage 1, early skarn (andradite–grossular assemblage); Stage 2, magnetite mineralization (diopside–magnetite assemblage); Stage 3, late skarn (amphibole–chlorite–epidote–johannsenite–hedenbergite–magnetite assemblage); Stage 4, sulfide mineralization (quartz–calcite–fluorite–chlorite–pyrite–galena–sphalerite assemblage); and Stage 5, carbonate (quartz–calcite assemblage). Fluid inclusion studies were carried out on inclusions in diopside from Stage 2 and in quartz, calcite, and fluorite from Stage 4.Halite-bearing (Type 1) and coexisting two-phase vapor-rich aqueous (Type 3) inclusions in the magnetite stage display homogenization temperatures of 448–564 °C and 501–594 °C, respectively. Salinities range from 26.5 to 48.4 and 2.4 to 6.9 wt% NaCl equivalent, respectively. Two-phase liquid-rich aqueous (Type 2b) inclusions in the sulfide stage yield homogenization temperatures and salinities of 182–343 °C and 1.9–20.1 wt% NaCl equivalent. These fluid inclusion data indicate that fluid boiling occurred during the magnetite stage and that fluid mixing took place during the sulfide stage. The former triggered the precipitation of magnetite, and the latter resulted in the deposition of Pb, Zn, and Fe sulfides. The fluids related to magnetite mineralization have δ¹⁸O_fluid-VSMOW of 6.7–9.6‰ and δD of −96 to −128‰, which are interpreted to indicate residual magmatic water from magma degassing. In contrast, the fluids related to the sulfide mineralization show δ¹⁸O_fluid-VSMOW of −0.85 to −1.04‰ and δD of −110 to −124‰, indicating that they were generated by the mixing of magmatic water with meteoric water. Magnetite grains from Stage 2 exhibit oscillatory zoning with compositional variations in major elements (e.g., SiO₂, Al₂O₃, CaO, MgO, and MnO) from core to rim, which is interpreted as a self-organizing process rather than a dissolution-reprecipitation process. Magnetite from Stage 3 replaces or crosscuts early magnetite, suggesting that later hydrothermal fluid overprinted and caused dissolution and reprecipitation of Stage 2 magnetite. Trace element data (e.g., Ti, V, Ca, Al, and Mn) of magnetite from Stages 2 and 3 indicate a typical skarn origin.     

沉积强度及氮养分改变对闽江河口短叶茳芏残体短期分解与养分释放的影响

互花米草入侵过程中较强的促淤作用可导致湿地沉积环境和养分状况发生明显变化.2017年4月,选择闽江河口鳝鱼滩西北部受互花米草入侵影响的短叶茳芏湿地为研究对象,基于野外原位沉积及养分改变模拟试验,设置无沉积强度(S0,0 cm·a-1)、当前沉积强度(S5,5 cm·a-1,氮养分水平为沉积物自然氮背景值)以及当前沉积强...     

Chemical compositions and cassfication of Grove Mountains （GRV） 98003 and other Chinese iron meteorites

Concentrations of Cr, Co, Ni, Cu, Ga, Ge, As, Sb, W, Re, Ir, Pt and Au of two ungrouped iron meteorites, Grove Mountains （GRV） 98003 from Antarctica and Ujimqin, were measured using instrumental neutron activation analysis. According to the bulk chemistry, GRV 98003 is classified as a member of ⅠAB group, and Ujimqin as a unique one of ⅠAB iron meteorite complex. The elemental abundance pattern and correlation between elements （e. g. Ni-Au, Co-Au, As-Au, W- Au, Cu-Au, Sb-Au） of GRV 98003 are similar with those of NAW 468 （ⅠAB）, but significantly depleted in refractory siderophile elements （ Re, It） and moderate volatile elements （Ca, Ge） relative to the latter. In addition, we reclassify Nantan （ⅢCD） as a member of ⅠAB main group （MG） and Yongning （ⅠA） as a unique iron meteorite related with IAB iron meteorite complex.     

阿尔金山喀腊大湾铁矿田地质特征与形成时代

阿尔金山喀腊大湾铁矿田位于北东向阿尔金走滑断裂与东西向阿尔金北缘断裂所夹持的地区。通过对已有铁矿床地质特征的研究,确认喀腊大湾地区铁矿床属于火山沉积型,因此,铁矿床具有成带状分布的特点,由八八铁矿床、八八西铁矿床、7914铁矿床、7915铁矿床、7918铁矿床和7910铁矿床共同构成喀腊大湾铁矿田。铁矿田范围内的地层以向北陡倾的单斜层为主,倾角75~88°;仅矿田西段八八西铁矿床、八八铁矿床一带沿走向发生直立陡倾伏(背斜)褶皱,可见地层和含矿岩系局部发生褶皱重复,形成铁矿带和含矿层位呈横卧"勾"状形态。铁矿床的产出严格受火山沉积岩系的特定层位和岩性控制,即铁矿床均产在卓阿布拉克组第三亚组第一岩性段(下部玄武岩段)的上部,其北侧为卓阿布拉克组第三亚组第二岩性段(大理岩段)标志层。与铁矿床关系密切的中基性火山岩锆石SHRIMP U-Pb年龄为(517±7)Ma,显示该套火山沉积岩系中基性火山岩的时代为早古生代晚寒武世,因此,铁矿床的形成(火山-沉积)时代为晚寒武世。铁矿床形成之后主要发生2期地质构造事件,其一是发生了构造变形,致使铁矿体及含铁岩系均呈陡立状态,并形成褶皱;其二是中酸性岩浆侵入活动,使已经形成的铁矿床受到中酸性侵入岩的吞食破坏,并发生接触变质矽卡岩化改造。矽卡岩化改造时代为早奥陶世末期(辉钼矿铼锇等时线年龄480 Ma)。     

Geochemistry and Genesis of Iron-apatite Ore in the Khanlogh Deposit, Eastern Cenozoic Quchan-Sabzevar Magmatic Arc, NE Iran

The Khanlogh deposit in the Cenozoic Quchan-Sabzevar magmatic belt, NE Iran, is hosted by Oligocene granodioritic rock. The Khanlogh intrusive body is I-type granitoid of the calc-alkaline series. The orebodies are vein, veinlet, massive, and breccia in shape and occur along the fault zones and fractures within the host rock. Ore minerals dominantly comprise magnetite and apatite associated with epidote, clinopyroxene, calcite, quartz, and chlorite. Apatites of the Khanlogh deposit have a high concentration of REE, and show a strong LREE/HREE ratio with a pronounced negative Eu anomaly. Magnetites have a high concentration of REE and show weak to moderate LREE/HREE fractionation. They are comparable to the REE patterns in Kiruna-type iron ores and show an affinity to calc-alkaline magmas. The Khanlogh deposit is similar in the aspects of host rock lithology, alteration, mineralogy, and mineral chemistry to the Kiruna-type deposits. Field observations, hydrothermal alteration halos, style of mineralization, and the geochemical characteristics of apatite, magnetite, and host rock indicate that these magnetite veins have hydrothermal origin similar to Cenozoic Kiruna-type deposits within the Tarom subzone, NW Iran, and are not related to silica-iron oxide immiscibility, as are the major Precambrian magnetite deposits in central Iran.     

闽西南马坑式铁矿成矿结构面特征及找矿意义

马坑式铁矿位于闽西南晚古生代坳陷盆地内,是福建省境内最主要的矽卡岩型铁-多金属矿床。矿体主要受岩性界面及构造结构面控制,尤以硅钙面控矿作用显著。马坑式铁矿主矿体定位于林地组（C₁l）石英砂岩与经畲—栖霞组（C₂j—P₂q）碳酸盐岩的岩性界面（硅钙面）。通过对马坑式铁矿硅钙面的基本特征进行分析,划分了五类主要的成矿结构面类型:林地组与经畲组—栖霞组、经畲组—栖霞组与文笔山组、经畲—栖霞组内部碎屑岩与灰岩、经畲组—栖霞组与花岗岩类以及推覆（滑脱）界面。研究认为马坑式铁矿主矿体受不同的物理化学岩性界面（硅钙面）控制,这种界面在构造活动及流体参与过程中容易形成扩容空间,构成成矿地球化学障,有利于成矿物质的沉淀富集。在以上认识基础上,建立了以硅钙面为主要成矿作用标志的马坑式铁矿成矿模式,认为运用硅钙面控矿理论指导闽西南地区找矿预测的具有重要的找矿指导意义。