川滇震旦系灯影组葡萄石的沉积环境

川镇地区震旦系地层发育，其中，灯影组含葡萄石。本文记述云南宜良九乡震旦系剖面以及川滇地区震旦系葡萄石，并探讨其沉积环境。     

葡萄石的热膨胀性与压缩性及其地质意义

利用同步辐射X射线衍射及拉曼光谱技术对葡萄石分别进行了原位高温及原位高压实验。原位高温实验结果表明葡萄石的热膨胀系数为K=1. 77(3)×10~(-5)K~(-1),轴向热膨胀系数具有各向异性(α_aα_bα_c),葡萄石在1073K时开始发生脱水反应,分解为钙长石及硅灰石。原位高压X射线衍射实验结果表明,在大于12. 4GPa时,葡萄石的晶胞参数发生不连续变化,可能发生了相变;在24. 0GPa左右,葡萄石发生不可逆的非晶化转变。原位高压拉曼光谱表明,葡萄石在12. 6GPa左右发生相变,这一相变很可能与其[(Si,Al)O_4]四面体中的Si发生有序排列有关。结合葡萄石的热膨胀性及压缩性,我们确定了葡萄石在高温高压下的稳定范围,这一结果对认识上地幔中含水矿物的状态以及地幔中水的来源有重要意义。     

会聚束电子衍射对葡萄石空间群的辅助测定

利用透射电子显微技术测定了湖北大冶铁山矿床中的微米级葡萄石空间群。选区电子衍射几何构图法分析表明,该矿物系斜方晶系,衍射消光符号为Ｐｎ－－晶胞参数为α＝０．４５８,ｂ＝０．５５５和ｃ＝１．８５３ｎｍ。（１００）和（３０１）方向的会聚束电子衍射花样研究表明,其空间群为Ｐｎｃｍ。     

黄色葡萄石的光谱学特征研究

利用傅里叶变换红外光谱仪、拉曼光谱仪和紫外可见光谱仪等测试分析手段,并结合偏光显微镜及常规宝石学方法,对黄色葡萄石样品进行了系统的测试研究。结果表明,黄色葡萄石具有典型的显微交织结构。红外吸收光谱和拉曼光谱显示了硅氧官能团的振动在900-1100cm~(-1)和400~800cm~(-1)波段产生特征吸收峰,同时OH~-的振动产生了3495cm~(-1)红外吸收峰和320cm~(-1)、390cm~(-1)拉曼吸收峰。紫外可见光谱显示,葡萄石具有430nm和580nm的吸收带,推断其黄色调是由Fe~(3+)致色形成的。     

含钙铝榴石的葡萄石—绿纤石相平衡：以新疆萨尔托海蛇绿岩中变基性岩石为例

利用矿物内部一致性热力学数据,建立了在ＣａＯ－Ａｌ２Ｏ３－ＭｇＯ－ＳｉＯ２－Ｈ２Ｏ体系中含钙铝榴石的葡萄石－绿纤石变质相平衡,确立了在葡萄石－绿纤石－钙铝榴石－绿帘石－绿泥石－石英组合中出现绿纤石－钙铝榴石共生、葡萄石－绿纤石共生、葡萄石－绿帘石共生和绿泥石－绿帘石－钙铝榴石共生的ＰＴ区间及其意义。根据该相平衡计算了新疆萨尔托海蛇绿岩中变基性岩石的葡萄石－绿纤石相变质ＰＴ条件为Ｔ＝３２５℃～３３５℃,Ｐ＝０．４５～０．４７５ＧＰａ。并讨论了Ｆｅ３＋＝Ａｌ替代对于形成钙铝榴石－绿纤石共生的影响。本文的研究表明,葡萄石－绿纤石－钙铝榴石－绿帘石－绿泥石－石英共生组合是葡萄石－绿纤石相中偏高压组合,钙铝榴石－绿纤石共生与绿纤石－阳起石相一样代表着葡萄石－绿纤石相中较高压相,钙铝榴石在葡萄石－绿纤石相中是可以稳定存在的。     

川东南地区灯影组葡萄石地球化学特征及成因分析

长期以来,人们对灯影组葡萄石的成因存在较大的争议。本文对灯影组葡萄石及基岩的地球化学特征进行了详细的对比分析,讨论了灯影组葡萄石的形成环境。灯影组葡萄石与基岩相比,具有较明显的Ce负异常和相对低的稀土总含量,说明了葡萄石并非是和基岩同时沉积而成;葡萄石中Na、K元素含量低而Mn、 Fe含量较高,具有很低的Sr/Ba比值,同时具有碳、氧同位素明显偏负和⁸⁷Sr/⁸⁶Sr值偏高的特点,表明葡萄石是在淡水的作用下形成的。证实了灯影组在沉积过程中有过一次短暂暴露过程,这次沉积间断使灯影组暴露地表接受淡水淋滤,形成了小规模的岩溶现象,为葡萄石的形成创造了条件。这次短暂暴露过程对人们更好地理解葡萄石的成因及灯影组中部储层的形成有重要的意义。     

粘土矿物中嵌晶态硅酸钴的浸取实验研究

系统地研究了用 Ｎ Ｈ４ Ｈ Ｆ２ 和柠檬酸浸取粘土矿物中嵌晶态硅酸钴的新方法。实验过程中对浸取剂的用量、水浴时间、温度等影响因素进行了正交实验设计,选出了最佳的浸取条件。结果表明,该方法浸取粘土矿物中嵌晶态硅酸钴的浸出率达 ９６０５％ 以上,相对标准偏差为１２２％ 。     

湖北大冶铁山铁矿床葡萄石和硅硼钙石矿物学特征及形成条件

大冶铁山铁矿床的葡萄石与硅硼钙石均产于夕卡岩的晶洞或裂隙中,与片沸石、菱沸石、辉沸石、方解石等密切共生。本文运用化学分析、X射线粉末衍射、红外吸收光谱和差热分析等现代测试方法,对葡萄石与硅硼钙石矿物学特征及形成条件进行了全面研究。     

Exhumation of the Dayman dome metamorphic core complex, eastern Papua New Guinea

The ～750 km² Dayman dome of the Late Cretaceous Suckling‐Dayman massif, eastern Papua New Guinea, is a domed landform that rises to an elevation of 2850 m. The northern edge of the dome is a fault scarp >1000 m high that is now part of an active microplate boundary separating continental crust of the New Guinea highlands from continental and oceanic crust of the Woodlark microplate. Previous work has shown that a parallel belt of eclogite‐bearing core complexes north‐east of the Dayman dome were exhumed from up to 24–28 kbar in the last few millions of years. The remarkably fresh and lightly eroded scarp of the Dayman dome exposes shallowly‐dipping mylonitic (S1) metabasite rocks (500 m thick) on the northern flank of Mount Dayman. Field relationships near the base of this scarp show a cross cutting suite of ductile and brittle meso‐structures that includes: (i) rare ductile S2 folia with a shallowly ESE‐plunging mineral elongation lineation defined by sodic‐calcic blue amphibole; (ii) narrow steeply‐dipping ductile D2 shear zones; and (iii) semi‐brittle to brittle fault zones. Pumpellyite‐actinolite facies assemblages reported by previous workers to contain local aragonite, lawsonite and/or glaucophane are found in the core of the complex at elevations greater than 2000 m. These assemblages indicate peak metamorphic pressures of 6–9.5 kbar, demonstrating exhumation of the core of the Dayman dome from depths of 20–30 km. The S1 metamorphic mineral assemblage in metabasite includes actinolite‐chlorite‐epidote‐albite‐quartz‐calcite‐titanite, indicative of greenschist facies conditions for the main deformation. New mineral equilibria modelling suggests that this S1 assemblage evolved at 5.9–7.2 kbar at ～425 °C. Modelling variable Fe³⁺ indicates that the sodic‐calcic blue amphibole (D2) formed under a higher oxidation state compared with the S1 assemblage, probably at <4.5 kbar. A SE‐dipping, Mio‐Pliocene sedimentary sequence (Gwoira Conglomerate) forms a hangingwall block juxtaposed by low‐angle fault contact with the metabasite footwall. Prehnite‐bearing D3 brittle fault zones separate the two blocks and likely accommodated the final exhumation of the S1 greenschist facies assemblage in the footwall. These results indicate that the extensive Mt Dayman fault surface coincides with a domed S1 greenschist facies foliation that was last active at >20 km depth. Exhumation of this foliation must therefore be controlled by brittle faults of the active microplate boundary that are largely not observed in the study area. The structural record of the final exhumation of the Dayman dome to the surface was likely lost as a result of erosion, poor exposure or wide spacing of semi‐brittle to brittle fault zones.     

萨碳硼镁钙石晶体结构的精确测定

本文对萨碳硼镁钙石(sakhaite)Ca_(48)Mg_(16)(BO_3)_(28)(CO_3)_(16)(Cl,F)_6(OH)_6·nH_2O的晶体结构进行了重新测定,求得晶胞参数:a=b=c=1.46151(9)nm。晶胞体积:V=3.1218(3)nm~3。单位晶胞中分子数Z=1,空间群为Fd3。结构测定的精度偏离因子R=0.0504。根据矿物化学成分及晶体结构特征,与前人报道的萨碳硼镁钙石及其人工合成矿物晶体结构特征进行了对比,指出本次测定的矿物与前人报道的天然萨碳硼镁钙石或人工合成矿物在矿物成分与结构上的差异,据此,讨论了我国产出的“萨碳硼镁钙石”有待重新命名的必要性。     

Isotope systematics of secondary minerals from the Prospect Intrusion,New South Wales

The differentiated Mesozoic alkali dolerite Prospect Intrusion contains a wide range of secondary minerals, including carbonates (primarily calcite), laumontite, prehnite and heulandite, whose stability relationships imply a formation temperature of <200°C. The δ¹⁸O data for carbonates define a higher temperature (160 – 195°C) suite, and a lower temperature (51 – 73°C) suite. The δ¹³C, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr isotope systematics for these carbonates suggest derivation of the higher temperature group from magmatic fluids, whereas the other group had a major meteoric component that probably originated from porewater in the country rock. Source fluids for prehnite were meteoric rather than magmatic in origin based on their δD and δ¹⁸O ratios. Early in the intrusion's emplacement, CO₂-rich hydrothermal fluids formed a carbonate rind sealing the upper part of the hydrothermal system and produced the higher temperature carbonates (calcite) and laumontite. Later, cooler fluids with a meteoric component infiltrated vesicles and fractures, depositing the lower temperature carbonates (calcite, aragonite), heulandite and prehnite.     

低温高压微地质体中微米纳米级矿物相研究——以大冶葡萄石中绿纤石和多硅白云母为例

低温高压地质体因与地壳碰撞、俯冲等构造活动密切相关,长期以来一直是国内外地学界关注的研究对象。但由于受研究手段、分辨能力所限,对于呈微米纳米级微粒形式存在于低温高压微地质体（即矿物）中的成分、物相及其成因等问题的研究,至今仍是地学研究中的薄弱环节。随...     

Automatic identification of rocks in thin sections using texture analysis

This paper presents a test of the automatic identification of photomicrographs of rocks in thin sections using digital image processing and texture analysis. Three sets of textural measures derived respectively from the cooccurrence matrix, texture space, and texture spectrum have been used to identify six rock types (mylonite, diorite porphyry, diorite. gabbro, granite, and peridotite). Exploring only the texture characteristics of images, the average correct recognition rate reaches 89% for 58 photographs belonging to the six types. The results also show the importance of using those more discriminating texture features in the classification algorithm. For the present study, the average rate of correct classification ranges from 46% to 89% depending on the set of texture measures used. The features extracted from the texture spectrum have more discriminating performance than the conventionally used Haralick measures derived from the cooccurrence matrix.     

Dehydration veins in diagenetic and very-low-grade metamorphic rocks: features of the crustal seismogenic zone and their significance to mineral facies

Abstract Declining temperatures during decay of a hydrothermal system, or during uplift and erosion, tend to result in veins involving progressive hydration reactions, e.g. veins with laumontite cutting prehnitepumpellyite facies rocks, and stilbite veins cutting laumontite veins. In contrast, examples are described of analcime replacement of heulandite along fractures in heulanditized vitric tuff, of replacement of analcime by albite along fractures in quartz-analcime rock, of joint-controlled replacement of heulandite in tuff by laumontite + quartz + (Na, K)-feldspars, of replacement of laumontite by prehnite + quartz along fractures in alumontitized vitric tuff, and of laumontitebearing feldspathic sandstones cut by vein assemblages of quartz and prehnite ° Calcite. The vein mineral assemblage, sometimes with pumpellyite and/or epidote in the prehnite-bearing veins, tends to spread as a zone of dehydration into the adjacent country rock. Except perhaps for albite replacement of analcime, and for laumontite replacement of heulandite, these open-system reactions involve cation activity ratios in the fluid. All involve dehydration. They are favoured by an increase in temperature, and except under certain situations where P-T equilibrium curves have negative slopes, are favoured by a fall in P_H2O. Evidence indicates that in at least some cases the triggering mechanism was a drop in P_H2O; this may be a widespread phenomenon associated with brittle fracture in the seismogenic upper crust. This may cause fluid pressure to drop from values approaching lithostatic to nearer hydrostatic, and equilibrium may be displaced to yield a less hydrous assemblage that appears as a dehydration vein and vein verge. The dehydration vein assemblage may be diagnostic of a higher grade mineral facies and adds to the mineral complexity attributable to varying permeabilities and fluid pressures in upper crustal strata. Mineral facies are likely to be more uniformly distributed in higher grade rocks from below the brittle-ductile transition zone. Reactions involving complex solid solutions are inappropriate as facies boundaries.     

The identification of organic input sources of sediments from the santa catalina basin using factor analysis

Individual neutral lipids, including hydrocarbons, ketones, alcohols, sterols, keto-ols and diols have been analysed from eight horizons in a sediment core taken from the Santa Catalina Basin, Calif. Variations in the concentration of individual lipid components between sites are studied using factor analysis to determine their inputs. Several sources of organic material are postulated from the composition of hypothetical factors, including methanogenic bacteria, higher plants and algae including coccolithophores, dinoflagellates and diatoms. Sources for long chain keto-ols and diols and a C₃₅ bicyclic alkene are suggested as methanogenic bacteria and algae respectively.     

草莓红绿柱石(Pezzottaite)的晶体结构测定及其意义

利用CCD单晶衍射仪对草莓红绿柱石进行晶体结构测定,测定其空间群为R3c,并讨论了结构中Li 有序地置换Be2 造成c/a值的变化特征。晶体中发现复三方偏三角面体的负晶包裹体,其宏观对称属m,它与空间群Rc相对应,但与测出晶体结构的空间群有矛盾。X射线结构测定已否定了其空间群为Rm的看法。要解决草莓红绿柱石晶体空间群是否有对称中心(Rc或Rc)的问题,还需进一步将X射线结构的数据及其有关的电性实验结合分析。