广西大厂拉么矿区萤石的稀土元素特征

随着测试技术的提高和地质研究的不断深入,稀土元素(REE)在地质上作为示踪剂愈益得到广泛应用.由于Ca~(2 )与REE~(3 )的晶体化学性质相近,并且在萤石中,Ca~(2 )的配位数为8,当REE~(3 )以类质同象替代Ca~(2 )进入萤石时,属于完全配分型,即萤石中的REE成份特征与其形成时熔(流)体的REE成份特征是一致的.因此,通过研究萤石的REE特征,     

游离氧化铁对红色粘土工程性质的影响

我国南方有许多含有大量游离氧化铁的红色粘土(砖红壤),它们是在湿、热成土条件下形成的,具有由成份和结构引起的特殊工程性质。它们往往含水量高,孔隙比大,但力学强度仍然较高,即存在所谓物理指标和力学参数似乎相互矛盾的现象。本文着重讨论游离氧化铁对砖红壤的工程性质(如强度、膨胀特性等)的影响。研究结果表明,土中的游离氧化铁的形成、淋失和结晶程度的不同,土的工程性质也各异;土的物理力学性质会随周围环境的物理化学因素变化而变化。     

天然钒钛磁铁矿中出溶现象的高分辨电镜观察

利用高分辨电子显微镜及微区X射线能谱成分测定的方法,对含钒的天然磁铁矿的精细结构进行了研究。结果表明,[110]方向的高分辨像清楚地显示钒钛磁铁矿在磁铁矿基体中以共(110)面紧密连生的方式与基体共生,形成波状连生体。这种成份调制波结构表明它们是出溶产物。     

含锰碳酸盐矿物中碳酸锰组份的定量测定

一、前言 含锰碳酸盐矿物是锰矿的重要工业类型之一,分布广泛,储量丰富。该类矿物中的Ca~( 2)、Mn~( 2)、Fe~( 2)等二价阳离子常常相互置换,形成完全的类质同象系列。这一系列矿物的化学组份变化大,成份复杂,光学性质及其它物理性质相似,易于混淆,难以鉴别。     

全风化花岗岩化学及矿物成份在全土和粘粒中的不同表征

对全风化花岗岩化学和矿物成份的测试常用全土和粘粒部分(粒径<2μm)分别进行。业已发现两者由于物质组成和结构特征的差异,对土工程地质性质所起作用不同。本文给出了6个全风化花岗岩样品的全土和粘粒部分筛分法和移液管法测定粒度成份,用X荧光光谱仪做全量化学分析,及XRD矿物学分析的结果。对比这两部分数据发现,属于含砾土的这些样品化学成份的变化同矿物一致,尤其是同粘土矿物成份含量变化很一致。同全岩相比,粘粒化学成份中的SiO₂减少了近50%,K₂O含量也降低,而Al₂O₃、Fe₂O₃和H₂O⁺都明显升高。粘粒中氧化物相对含量升高者居多;全岩矿物成份以石英、粘土矿物和长石为主,粘粒中埃洛石和高岭石占大多数,其次为伊利石;粒度成份、化学成份和矿物含量相关性比较明显的是:石英和角砾正相关,和砂粒负相关,长石和砂粒正相关,粘土矿物含量和Al₂O₃、烧失量(LOI)和埃洛石含量正相关。     

贵州镇远,台江地区铅锌矿地质特征及找矿前景

镇远、台江地区铅锌矿,严格受下江群平略组(Pt_3p)及清水江组二段(pt_3g~2)层位制约。矿体形态简单,围岩蚀变微弱,矿石物质成份和矿物成份十分简单,铅锌矿与岩浆活动没有时间和空间上的联系,为层控型铅锌矿。     

在野外如何以肉眼鉴别长石类矿物

岩浆岩,特别是期中的花岗岩类岩石,不仅分布广泛,而且与绝大多数的金属矿床有着密切的成因联系。在岩浆岩中,仅仅除了超基性岩之外,长石矿物几乎是所有其余岩浆岩个可缺少和唯一主要的矿物成份。尤其是斜长石类,由于它们广泛的并按自已成份的变化(Ca 与 Na 含量比例的变化),而有规律性的出现在酸性到基性岩浆岩中,因而就成了鉴定岩浆岩(包括肉眼和镜下)唯一重要的标志了。所以,在野     

宇宙成因核素~(10)Be、~(36)C1及其加速器质谱测定

~(10)Be、~(36)Cl是宇宙射线与大气成份进行散裂核反应的产物。它们在大气圈停留1—2年,然后通过降水沉降至地表。~(10)Be半衰期1.5×10~6a,~(36)Cl半衰期0.301×10~6a,均属纯β放射体,在自然界含量极低,传统的衰变测量法已难以适应现代地球科学中高分辨研究的需要,七十年代末八十年代初兴起的加速器质谱技术使这两核素的测量灵敏度提高了五个数     

大兴安岭森林覆盖区金矿土壤离子电导率异常特征离子成份的研究及找矿预测

为了解森林覆盖区金矿体土壤离子电导率异常特征,探讨金矿体土壤离子电导率成份是由哪些种类离子组成,弄清不同种类离子的含量变化关系对电导率的贡献大小,为解释金矿土壤离子电导率异常的形成机制提供理论依据.通过在大兴安岭森林覆盖区虎拉林金矿的研究:(1)在已知的金矿体上测出了清晰的电导率异常,异常呈典型双峰形态"兔耳"状或"锯齿"状, 异常垂直指示金矿体的赋存位置.(2)弄清了金矿体组成土壤离子电导率异常的离子成份特征,其成份主要是HCO-3、SO-24、Ca2 、Cl-、K 、Na 、F-、Mg2 、Mn2 等一套水可溶性离子,经过相关分析得出金矿电导率异常与各水可溶性离子的相关系数是HCO-3＞Ca2 ＞SO2-4＞Cl-＞K ＞F-＞Na ＞Mg2 ＞Mn2 .(3)在未知区的找矿预测中找到3个具有成矿远景的离子电导率异常.     

识别华南燕山期含锡花岗岩的岩石化学方法及其在新路矿区的应用

本文对比华南燕山期同属钛铁矿系列和S型的含锡与贫锡花岗岩的化学成份,发现(1)前者含SiO_2、Na_2O、P_2O_5较高,其它常量元素及K_2O+Na_2O、K_2O/Na_2O较低。差异的原因可能是:含锡花岗岩演化得更充分,且形成于fO_2较低,含挥发份较高的条件下;(2)戈蒂尼指数τ-SI、M-F,il-hy中en(CIPW标准矿物)等图解及根据贝叶斯准则建立的两个判别函数,可较有效地区分含锡与贫锡花岗岩。此方法在新路矿区应用取得了较好的效果。     

新疆蒙库铁矿床矽卡岩矿物学特征及其意义

蒙库铁矿床是一个以下泥盆统斜长角闪变粒岩(原岩为火山岩)为围岩的大型矽卡岩型矿床,矽卡岩矿物组合为辉石、石榴子石和方柱石,退化蚀变岩的组成矿物为角闪石、绿帘石、绿泥石、磷灰石等。电子探针分析结果表明,矽卡岩矿物中单斜辉石以透辉石为主,仅存在少量普通辉石;石榴子石端员组分以钙铁榴石为主,伴以少量钙铝榴石和锰铝榴石;角闪石属于单斜角闪石中的阳起石。蒙库铁矿床的矽卡岩与正常的矽卡岩矿床形成方式不同,不是中酸性岩浆与碳酸盐地层接触交代的产物,而是由热流体沿裂隙交代火山变质岩形成的。     

Pumpellyite–actinolite facies of the Sanbagawa metamorphism

The pumpellyite–actinolite facies proposed by Hashimoto is defined by the common occurrence of the pumpellyite–actinolite assemblage in basic schists. It can help characterize the paragenesis of basic and intermediate bulk compositions, which are common constituents of various low-grade metamorphic areas. The dataset of mutually consistent thermodynamic properties of minerals gives a positive slope for the boundary between the pumpellyite–actinolite and prehnite–pumpellyite facies in P–T space. In the Sanbagawa belt in Japan, the mineral parageneses of hematite-bearing and -free basic schists, as well as pelitic schists have been well documented. The higher temperature limit of this facies is defined by the disappearance of the pumpellyite+epidote+actinolite+chlorite assemblage in hematite-free basic schists with X_Fe3+ of epidote around 0.20–0.25 and the appearance of epidote+actinolite+chlorite assemblage with X^Ep_Fe3+≤0.20. In hematite-bearing basic schists, there is a continuous change of paragenesis to higher grade, epidote–glaucophane or epidote–blueschist facies. In pelitic schists, the albite+lawsonite+chlorite assemblage does occur but only rarely, and its assemblage cannot be used to determine the regional thermal structure. The lower temperature equivalence of the pumpellyite–actinolite assemblage is not observed in the field. The Mikabu Greenstone complex and the northern margin of the Chichibu complex, which are located to the south of the Sanbagawa belt, are characterized by clinopyroxene+chlorite or lawsonite+actinolite assemblages, which are lower temperature assemblages than the pumpellyite+actinolite assemblage. These three metamorphic complexes belong to the same subduction-metamorphic complex. The pumpellyite–actinolite facies or subfacies can be useful to help reveal the field thermal structure of metamorphic complexes     

Phase equilibria among pumpellyite,lawsonite, epidote and associated minerals in low grade metamorphic rocks

Phase relations of pumpellyite, epidote, lawsonite, CaCO₃, paragonite, actinolite, crossite and iron oxide are analysed on an Al-Ca-Fe³⁺ diagram in which all minerals are projected from quartz, albite or Jadeite, chlorite and fluid. Fe²⁺ and Mg are treated as a single component because variation in Fe²⁺/Mg has little effect on the stability of phases on the diagram. Comparison of assemblages in the Franciscan, Shuksan, Sanbagawa, New Caledonia, Southern Italian, and Otago metamorphic terranes reveals several reactions, useful for construction of a petrogenetic grid:

1. lawsonite+crossite + paragonite = epidote+chlorite + albite + quartz + H₂O
2. lawsonite + crossite = pumpellyite + epidote + chlorite + albite+ quartz + H₂O
3. crossite + pumpellyite + quartz = epidote + actinolite + albite + chlorite + H₂O
4. crossite + epidote + quartz = actinolite + hematite + albite + chlorite + H₂O
5. calcite + epidote + chlorite + quartz = pumpellyite + actinolite + H₂O + CO₂
6. pumpellyite + chlorite + quartz = epidote + actinolite + H₂O

     

Chadormalu Kiruna-type magnetite-apatite deposit,Bafq district,Iran: Insights into hydrothermal alteration and petrogenesis from geochemical,fluid inclusion,and sulfur isotope data

The Chadormalu is one of the largest known iron deposits in the Bafq metallogenic province in the Kashmar-Kerman belt, Central Iran. The deposit is hosted in Precambrian-Cambrian igneous rocks, represented by rhyolite, rhyodacite, granite, diorite, and diabasic dikes, as well as metamorphic rocks consisting of various schists. The host rocks experienced Na (albite), calcic (actinolite), and potassic (K-feldspar and biotite) hydrothermal alteration associated with the formation of magnetite–(apatite) bodies, which are characteristic of iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) systems. Iron ores, occurring as massive-type and vein-type bodies, consist of three main generations of magnetite, including primary, secondary, and recrystallized, which are chemically different. Apatite occurs as scattered irregular veinlets in various parts of the main massive ore-body, as well as apatite-magnetite veins and disseminated apatite grains in marginal parts of the deposit and in the immediate wall rocks. Minor pyrite occurs as a late phase in the iron ores. Chemical composition of magnetite is representative of an IOA or Kiruna-type deposit, which is consistent with other evidence.Whole rock geochemical data from various host rocks confirm the occurrence of Na, Ca, and K alteration consistent with the formation of albite, actinolite, and K-feldspar, respectively. The geochemical investigation also includes the nature of calc-alkaline igneous rocks, and helps elaborating on the spatial and temporal association, and possible contribution of mafic to felsic magmas to the evolution of ore-bearing hydrothermal fluids.Fluid inclusion studies on apatites from massive- and vein-type ores show a range of homogenization temperatures from 266 to 580 °C and 208–406 °C, and salinities from 0.5 to 10.7 wt.% and 0.3–24.4 wt.% NaCl equiv., respectively. The fluid inclusion data suggest the involvement of evolving fluids, from low salinity-high temperature, to high salinity-low temperature, in the formation of the massive- and vein-type ores, respectively. The δ³⁴S values obtained for pyrite from various parts of the deposit range between +8.9 and +14.4‰ for massive ore and +18.7 to +21.5‰ for vein-type ore. A possible source of sulfur for the ³⁴S-enriched pyrite would be originated from late Precambrian-early Cambrian marine sulfate, or fluids equilibrated with evaporitic sulfates.Field observations, ore mineral and alteration assemblages, coupled with lithogeochemical, fluid inclusion, and sulfur isotopic data suggest that an evolving fluid from magmatic dominated to surficial brine-rich fluid has contributed to the formation of the Chadormalu deposit. In the first stages of mineralization, magmatic derived fluids had a dominant role in the formation of the massive-type ores, whereas a later brine with higher δ³⁴S contributed to the formation of the vein-type ores.     

新疆和静县查岗诺尔铁矿床FeⅠ矿体围岩蚀变特征

新疆和静县查岗诺尔铁矿床位于伊犁微板块北缘之博洛科努早古生代岛弧带,属于阿吾拉勒金、铜、铅、锌、铁成矿带东段。矿区出露地层主要为下石炭统大哈拉军山组火山岩和上石炭统伊什基里克组火山岩,两者为断层接触关系。由于成矿矿浆的多期次活动,查岗诺尔铁矿广泛发育围岩蚀变,形成沿断裂带分布的带状蚀变带。通过研究发现,矿床主矿体FeⅠ号主矿体的围岩蚀变情况,按不同蚀变矿物组合,自东向西可分出石榴石带、绿帘石-阳起石带、阳起石-磁铁矿带、蚀变大理岩带和阳起石带,对应三期蚀变作用。各阶段的矿物共生组合分别为：磁铁矿＋透辉石＋石榴石、磁铁矿＋阳起石＋绿帘石、磁铁矿-石榴石-阳起石-绿帘石-石英-碳酸盐。矿区蚀变是由高、中温火山热液交代中酸性火山碎屑岩而形成。     

Phase relations of biotite and stilpnomelane in the greenschist facies

Phase relations of biotite and stilpnomelane and associated silicate minerals have been studied in rocks of the greenschist facies, chiefly from Otago, New Zealand and western Vermont, but also from Scotland, Minnesota-Michigan iron range, and northwest Washington. That stilpnomelane in the greenschicht facies crystallizes initially with nearly all iron in the ferrous state is indicated by chemical analyses, high p-T experiments, and phase relationships. Alteration of stilpnomelane after metamorphism not only oxidizes iron but leaches potassium; corrections for both effects must be made in using analyses of brown stilpnomelane in studies of phase relations. Two discontinuous reactions which produce biotite at the biotite isograd have been identified:

1. muscovite+stilpnomelane+actinolite→ biotite+chlorite+epidote
2. chlorite+microcline→ biotite+muscovite. Biotite produced by the first of these reactions has a limited range of variation in Fe/Mg. As grade advances within the biotite zone more magnesian and ferruginous biotites become stable in consequence of the two continuous reactions:
3. muscovite+actinolite+chlorite→ biotite (Mg-rich)+epidote
4. muscovite+stilpnomelane→ biotite (Fe-rich)+chlorite.

Stilpnomelane is stable in muscovite-free rocks throughout the biotite zone, and even up to the grade at which hornblende becomes stable. Phengitic muscovite is stable throughout the biotite zone in New Zealand and thus apparently does not contribute to the formation of biotite until a higher grade is reached.     

Lawsonite zone blueschists and a sodic amphibole producing reaction in the Tavşanli Region,Northwest Turkey

The petrology and mineralogy of lawsonite zone metabasites have been studied northeast of town of Tav?anli, NW Turkey. In the field the metabasites are characteristically green and lack foliation; the essential mineral assemblage being sodic pyroxene+ lawsonite+chlorite+quartz±sodic amphibole. Sodic pyroxene of aegirine-jadeite composition occurs as pseudomorphs after magmatic augite. Lawsonite and chlorite are the other two dominant minerals. Sodic amphibole forms progressively from a reaction between sodic pyroxene, chlorite and quartz, and an isograd representing the first abundant occurrence of sodic amphibole in basic rocks has been mapped. The widespread occurrence of sodic pyroxene pseudomorphs in other blueschist terrains indicates that the inferred sodic amphibole producing reaction is of general significance for blueschist metabasites.The conversion of greenstones with the assemblage albite+chlorite+actinolite directly into glaucophane-lawsonite blueschists without any intervening lawsonite zone illustrates the influence of the initial mineral assemblage on the reaction path.     

Effect of the disproportionation reaction of ferrous iron in impact-evaporation processes

Evidence for the disproportionation of iron was found in model experiments imitating impact melting, evaporation, and condensation. The experiments were carried out using a laser system at a characteristic temperature of ～3000–4000 K and a pulse duration of ～10^?3 s in a He atmosphere (P = 1 atm). Augite and mixtures of peridotite with MnO₂ and WO₃ were used as starting target materials. Experimental products (condensed vapor phase) were analyzed by X-ray photoelectron spectroscopy. The results of condensate analysis provided compelling evidence for the presence of iron in three oxidation states (Fe⁰, Fe²⁺, and Fe³⁺). In an experiment with augite, the proportions of iron species of different valences were similar to the stoichiometry of the disproportionation reaction. Similar evidence for this reaction was first found in a condensate from the samples of the fine fraction of the Luna 16 regolith. In the layers of the lunar condensate, the proportions of the valence states of iron were on average Fe⁰:Fe²⁺:Fe³⁺ = 1.2: 1.9: 0.7.     

Determination of Fe3+ and Fe2+ concentrations in feldspar by optical absorption and EPR spectroscopy

Ferrous and ferric iron concentrations in feldspars with low total iron content (<0.32 wt% total Fe) were determined from optical and electron paramagnetic resonance (EPR) spectra to better than ±15 percent of the amount present. Optical spectra indicate that Fe²⁺ occupies two distorted M-sites in plagioclases of intermediate structural state. The linear dependence of the Fe²⁺/Fe total ratio on An content demonstrates that Fe²⁺ substitutes for Ca (not Na) so that the number of Ca-sites is a principal factor in iron partitioning in plagioclase. EPR powder spectra show that the number of sites for Fe³⁺ depends on structural state rather than on plagioclase chemistry. The observed linear correspondence of EPR double-integrated intensities with optical peak areas shows that all Fe³⁺ is tetrahedrally coordinated in both plagioclase and disordered potassium feldspar. Microcline perthites show, in addition to tetrahedral Fe³⁺, a signal due to axially coordinated ferric iron, which we associate with formation of hematite inclusions.     

P–T–X controls on phase stability and composition in LTMP metabasite rocks – a thermodynamic evaluation

The stability of pumpellyite + actinolite or riebeckite + epidote + hematite (with chlorite, albite, titanite, quartz and H₂O in excess) mineral assemblages in LTMP metabasite rocks is strongly dependent on bulk composition. By using a thermodynamic approach (THERMOCALC), the importance of CaO and Fe₂O₃ bulk contents on the stability of these phases is illustrated using P–T and P–X phase diagrams. This approach allowed P–T conditions of ～4.0 kbar and ～260 °C to be calculated for the growth of pumpellyite + actinolite or riebeckite + epidote + hematite assemblages in rocks containing variable bulk CaO and Fe₂O₃ contents. These rocks form part of an accretionary wedge that developed along the east Australian margin during the Carboniferous–Triassic New England Orogen. P–T and P–X diagrams show that sodic amphibole, epidote and hematite will grow at these conditions in Fe₂O₃‐saturated (6.16 wt%) metabasic rocks, whereas actinolite and pumpellyite will be stable in CaO‐rich (10.30 wt%) rocks. With intermediate Fe₂O₃ (～3.50 wt%) and CaO (～8.30 wt%) contents, sodic amphibole, actinolite and epidote can coexist at these P–T conditions. For Fe₂O₃‐saturated rocks, compositional isopleths for sodic amphibole (Al³⁺ and Fe³⁺ on the M2 site), epidote (Fe³⁺/Fe³⁺ + Al³⁺) and chlorite (Fe²⁺/Fe²⁺ + Mg) were calculated to evaluate the efficiency of these cation exchanges as thermobarometers in LTMP metabasic rocks. Based on these calculations, it is shown that Al³⁺ in sodic amphibole and epidote is an excellent barometer in chlorite, albite, hematite, quartz and titanite buffered assemblages. The effectiveness of these barometers decreases with the breakdown of albite. In higher‐P stability fields where albite is absent, Fe²⁺‐Mg ratios in chlorite may be dependent on pressure. The Fe³⁺/Al and Fe²⁺/Mg ratios in epidote and chlorite are reliable thermometers in actinolite, epidote, chlorite, albite, quartz, hematite and titanite buffered assemblages.