维拉斯托稀有金属-锡多金属矿床铌铁矿族矿物特征及其对岩浆-热液演化的指示

大兴安岭南段维拉斯托大型稀有金属-锡多金属矿床的成矿岩体从深部的中粒花岗岩向上逐渐过渡为斑状细粒碱长花岗岩,记录了岩浆演化的不同阶段。为查明铌铁矿族矿物成分、结构变化及其与岩浆演化过程的耦合关系,文章对采自不同深度的3种类型花岗岩（中粒花岗岩、石英斑晶不具雪球结构的斑状细粒富云母碱长花岗岩和具雪球结构的斑状细粒碱长花岗岩）中的铌铁矿族矿物进行了详细的电子探针成分分析和元素面扫工作。维拉斯托矿床铌铁矿族矿物主要为铌铁矿,发育渐变环带结构,从核部到边部Ta含量增加,且斑状细粒富云母碱长花岗岩和斑状细粒碱长花岗岩铌铁矿族矿物边部的铌铁矿、铌锰矿相较于幔部和核部的铌铁矿,其Ta含量具有明显的组分间隔;铌铁矿族矿物Mn/(Fe+Mn)原子比具有多种演化趋势,与分离结晶的矿物相和流体交代作用有关。中粒花岗岩和斑状细粒富云母碱长花岗岩中的铌铁矿结晶于岩浆阶段,斑状细粒碱长花岗岩中的铌铁矿族矿物结晶于岩浆-热液过渡阶段。其中,斑状细粒富云母碱长花岗岩铌铁矿边部Ta含量增加与铁锂云母的分离结晶作用有关,斑状细粒碱长花岗斑岩铌铁矿族矿物边部Ta含量的突变与岩浆-热液过渡阶段的水硅酸盐液体中Ta溶解度的增加...     

西南天山科桑溶洞新元古代-早奥陶世花岗岩锆石U-Pb年代学研究

在新疆西南天山科桑溶洞地区,新厘定出一套斜长角闪岩-花岗岩地质单元:侵入斜长角闪岩中的新元古代白云母花岗岩(片麻状构造)、以及侵入上述古老岩石单元的早奥陶世花岗岩(块状构造)。片麻状白云母花岗岩中锆石具有热液锆石边、岩浆锆石幔和碎屑锆石核(边-幔-核结构),剔除被热液锆石和碎屑锆石混染的SHRIMP测点,获得岩浆锆石幔的加权平均年龄752.3±5.1Ma(MSWD=0.95),代表岩浆的结晶年龄。块状花岗岩的锆石具有边-核结构,热液锆石边的U-Pb年龄(419.5±5.7Ma)明显偏低。剔除热液锆石和碎屑锆石,获得岩浆锆石的平均U-Pb年龄481.1±4.4Ma(MSWD=0.88),代表花岗岩的结晶年龄。早奥陶世早期,岩浆侵入新元古代片麻状白云母花岗岩中。在晚志留世或者更晚时期,两类花岗岩共同经受了变质热液改造,变质流体交代岩浆锆石,导致锆石溶蚀再生长。     

云南六合正长斑岩中花岗岩包体锆石U-Pb定年及其地质意义

滇西地区沿金沙江-哀牢山断裂带广泛发育新生代富碱斑岩,其中六合富碱斑岩中发现了与镁铁-超镁铁质深源包体紧密共生的花岗岩包体。本文对花岗岩包体中锆石进行了阴极发光图像、LA-ICP-MS微量元素分析和U-Pb定年研究。研究表明,该花岗岩包体中锆石可分为岩浆锆石、老核新壳的复合岩浆锆石和变质交代成因锆石;复合岩浆锆石的新壳206Pb/238U平均加权年龄为39.2±2Ma,代表花岗岩包体的成岩年龄,与寄主富碱斑岩的成岩年龄基本一致;复合岩浆锆石的老核206Pb/238U平均加权年龄为828.1±7.1Ma,代表基底岩石年龄。变质锆石的206Pb/238U平均加权年龄为108.4±4.4Ma,与角闪石化金云石榴透辉岩中角闪石Ar-Ar年龄102.87±1.19Ma基本吻合,代表地幔流体交代矿物的结晶年龄,表明地幔流体交代作用过程可能在白垩纪前后延续一个相当长的时期。结合岩相学研究,认为该花岗岩包体被捕获运移时处于熔融态;花岗质熔浆的形成很可能与地幔流体作用引发的地壳部分熔融与壳幔岩浆混合作用密切相关。     

五大连池钾质火山岩中的壳源捕虏体特征及地质意义

黑龙江省五大连池钾质火山岩石中普遍含有壳源捕虏体和捕虏晶,并多赋存于火山集块、浮岩砾、火山渣等各级火山碎屑物及盾状台地的表皮相到内部相火山熔岩中。花岗岩质捕虏体一般大小为5～50cm,捕虏晶一般为0.2～5mm,成分以二长花岗岩为主,少见花岗闪长岩及黑云母英云闪长岩和少量砂岩捕虏体。石英、斜长石、少数钾长石捕虏晶见于各期火山碎屑(物)和熔岩中,其中以石英捕虏晶最为常见。壳源捕虏体中的代表性矿物及浅色玻璃电子探针分析结果表明,火山岩SiO2偏高是岩浆上涌喷发过程中捕获了大量壳源物质的结果。五大连池火山群富钾火山岩岩石化学、地球化学长期保持均一,说明其岩浆直接来自EMⅠ型钾质地幔,岩浆在上升过程中遭受了地壳物质的明显混染。     

滇西六合正长斑岩和花岗岩包体中锆石U-Pb年代和微量元素地球化学研究

六合正长斑岩是滇西新生代富碱斑岩的典型代表,以发育各类深浅不一的岩石包体而闻名,其中包括了同期的花岗岩包体;主岩和包体所蕴含的深部地质过程对于富碱岩浆的形成和演化具有重要约束作用。本文以六合正长斑岩和其中花岗岩包体的锆石微量元素地球化学为研究重点,结合主岩主量元素、锆石U-Pb年龄、Ti温度、锆石氧逸度的对比研究,分析和探讨富碱岩浆的形成和演化过程。研究表明:锆石U-Pb年龄所限定的六合富碱岩浆活动时限为(37.89±0.96)~(35.87±0.58) Ma;而花岗岩包体代表的同期富硅酸性岩浆活动时限为(38.21±0.44)~(36.21±0.36) Ma;两者几乎同步活动。锆石微量元素成因判别图显示主岩锆石主要位于钾镁煌斑岩范围,暗示富碱岩浆源区具地幔属性;花岗岩包体锆石大多位于花岗岩范围,两者在花岗岩范围有部分重叠,证实了主岩锆石和花岗岩包体锆石结晶时存在共同的生长环境。Ce^(Ⅳ)/Ce^(Ⅲ)比值估算和Ti温度计算显示,在36.42~36.41 Ma范围内富碱岩浆氧逸度和锆石结晶温度发生突变,指示在该时限内富碱岩浆及所裹挟的花岗质岩浆发生了混合作用;氧逸度的振荡降低反映了后期幔源岩浆的补充。综合研究认为,六合地区来自富集地幔的喜山期富碱岩浆底侵熔化上覆深部地壳长英质岩石形成花岗质岩浆,随即以富碱岩浆为主与少量花岗质岩浆不均一混合并同步结晶成岩形成含有花岗岩包体的正长斑岩。     

西准噶尔紫苏花岗岩成因岩石学研究

紫苏花岗岩呈岩体形式侵入于石炭纪地层中．又为碱长花岗岩侵入．紫苏花岗岩由斜方辉石、单斜辉石、铁橄榄石、条纹长石、石英组成．以正εNd为特征(εNd= 4．8- 5．8)矿物组成、结构和野外产状表明：这些紫苏花岗岩是火成成因的．温压计算估测其结晶条件是T=700～800℃，P=420～575kPa．紫苏花岗岩中有小的富云母包体和巨大的条带状捕虏体．前被认为是残留体，后与其围岩．火山碎屑岩相当．残留体中较低的εNd正值(εNd= 2．6- 3．5)要求新生的下部地壳是紫苏花岗岩的主要源岩：来自这些源岩的紫苏花岗岩的母岩浆在结晶前与一些来自于亏损地幔中的融体混合．该地区体积巨大的碱性花岗岩可能也来自相同的岩浆源，只不过它是在较浅的地壳深度上结晶的．     

赣西大港花岗岩型锂矿床锂赋存状态及成岩成矿年代学

大港锂矿床是赣西地区近年来新探明的超大型花岗岩型锂矿之一,成矿与白云母花岗岩密切相关.研究开展了云母矿物学特征及电子探针分析确定锂赋存状态,并利用锆石和锡石LA-ICPMS U-Pb定年法对白云母花岗岩进行了系统的年代学研究,精确厘定成岩成矿时代.年代学结果显示I型热液锆石Tera-Wasserburg U-Pb下交点年龄为129±2 Ma,而颜色较暗的II型锆石下交点年龄为100±4 Ma.锡石核部和边部Tera-Wasserburg U-Pb下交点年龄分别为125±3 Ma和108±7 Ma,同期结果与锆石年龄在误差范围内一致.这些年龄数据显示大港锂矿呈多期次成矿特点.成矿作用均形成于早白垩世,与江南造山带中段燕山期大规模稀有金属成矿时限一致.大港锂矿床中云母主要为富锂白云母、铁锂云母和锂云母,且云母具有明显环带特征,边部较核部富Si、Li和F等元素.云母微观结构及矿物化学特征表明大港高演化花岗岩型锂矿床经历了早期岩浆分异和晚期热液交代两个阶段.晚期富氟富锂热液对白云母花岗岩进行了强烈的交代改造,使锂元素在云母边部高度富集,从而形成富锂矿物.九岭南缘高演化花岗岩型锂矿床的厘定指示了...     

黑龙江省毛家屯花岗岩中碱性暗色矿物特征及其地质意义

碱性暗色矿物作为具有特殊指示意义的矿物,其存在对岩浆演化过程具有重要的意义。毛家屯花岗岩体位于兴蒙造山带东部的小兴安岭—张广才岭南段,岩体内部发育碱性暗色矿物。以毛家屯岩体内部发育的碱性暗色矿物为研究对象,进行了矿物学和矿物化学电子探针分析。研究表明,碱性角闪石的类型为铁-镁铝钠闪石,具有富碱,尤其富钠、富硅、富铁、贫钙、镁、钛等特征。辉石的类型为霓辉石,化学特征上高硅-高钠,高铁,低钛、镁、铝、锰。碱性暗色矿物主岩为碱性岩,成因类型为铝质A型花岗岩类。毛家屯花岗岩碱性角闪石具有很低的M值,证明其来源于地壳物质的熔融。毛家屯花岗岩中碱性角闪石的特征指示,在结晶过程中,岩浆体系处于封闭还原条件,且岩体从中央到边部存在偏酸性和偏基性组分分带现象。结合前人的同位素和年代学方面的分析资料,认为毛家屯碱性花岗岩形成于造山后期伸展转换环境中。     

巴尔哲超大型稀有稀土矿床富晶体的流体包裹体初步研究

巴尔哲矿床是一个超大型稀有稀土多金属矿床,它受巴尔哲碱性花岗岩体（株）控制,稀有稀土矿体分布在巴尔哲岩体上部的钠长石碱性花岗岩中。本文在钠长石碱性花岗岩的石英中发现了大量的富晶体的流体包裹体,并对其进行了初步的激光拉曼光谱和显微测温研究。与一般含盐类晶体矿物的三相流体包裹体不同,巴尔哲富晶体的流体包裹体的晶体不是盐类矿物,而是长石、云母等硅酸盐矿物;同时,该类包裹体内还广泛分布着稀土碳酸盐矿物。富晶体的流体包裹体的发现从微观角度揭示了巴尔哲含矿钠长石碱性花岗岩的形成与岩浆-热液过渡阶段有直接的成因联系,并为阐述巴尔哲岩体稀土元素及氧同位素的地球化学特征提供了新思路。稀土碳酸盐矿物在富晶体的流体包裹体中广泛地分布则充分说明。巴尔哲碱性花岗岩演化到岩浆-热液过渡阶段体系内的稀土元素已经达到足以形成独立稀土矿物的富集程度,其稀土元素矿化受岩浆-热液过渡阶段的制约。     

白云母成分对富锂铍伟晶岩成因的指示：以卡鲁安稀有金属矿田为例

新疆阿尔泰造山带是我国重要的稀有金属矿床矿产资源基地,尤以富Li和富Be伟晶岩型矿床广泛发育为特色。本研究选择阿尔泰造山带卡鲁安-阿祖拜矿田富Li和富Be伟晶岩型矿床开展典型解剖,以贯穿岩浆阶段-伟晶岩阶段的白云母矿物为研究主线,探讨不同矿化类型伟晶岩中云母的成分演化规律、花岗岩与伟晶岩的成因联系。矿物学特征显示富Be伟晶岩中发育大量磷酸盐矿物,而富Li伟晶岩含较多橙色锰铝榴石、锂云母而缺乏典型的Fe-Mn磷酸盐。白云母成分分析显示,从白云母花岗岩→富Be伟晶岩→富Li伟晶岩,白云母总体呈Nb含量和Nb/Ta值降低,指示白云母花岗岩、富Be伟晶岩经历了不同程度的分离结晶作用,也代表了富Li伟晶岩的岩浆分异演化程度更高。尽管利用云母成分变化(尤其是K、Rb、Cs等大离子亲石元素)模拟岩浆结晶演化过程,显示可由初始花岗质岩浆经瑞利分离结晶作用依次形成白云母花岗岩→富Be伟晶岩→富Li伟晶岩的假设。但研究区年代学、矿物学、同位素证据指示富Li伟晶岩和富Be伟晶岩具有不同的熔体性质和形成时代。因此,应用云母成分探讨伟晶岩的成因联系应当建立在花岗岩-伟晶岩系统具有合理的时空分布和其它支持源自同一...     

嫦娥五号返回月壤微观形貌特征及其对太空风化的指示意义

研究识别嫦娥五号返回月壤样品颗粒的类型、含量、形貌、结构和成分特征,可为嫦娥五号着陆区月壤的成因与月球表面演化过程提供关键科学依据.利用扫描电镜-能谱仪、矿物自动定量分析系统和显微激光拉曼光谱仪对嫦娥五号表取月壤样品CE5C0400（YJFM00403）进行了系统研究,发现月壤颗粒组成多样,包括斜长石、单斜辉石和橄榄石等矿物、玄武岩碎屑、黏结物和玻璃球.颗粒表面和内部微观结构复杂,呈现各种破碎、表面附着堆积、微撞击坑、溅射物等形式的微米-纳米级的形貌特征.嫦娥五号月壤的微形貌特征记录了以微陨石撞击为主导的复杂太空风化过程:一方面反复的撞击作用使月壤颗粒破碎、粒度变细,另一方面撞击引发的局部熔融又使颗粒发生胶结,同时伴随含铁矿物分解形成微-纳米级单质铁颗粒.上述过程反复进行,导致月壤颗粒大小和物相组成复杂多变.      

南岭地区钨锡花岗岩的成矿矿物学：概念与实例

南岭地区的钨锡成矿作用与花岗岩岩浆活动有十分密切的关系。花岗岩的物源与成矿元素的初始富集、花岗岩的分异程度和花岗岩中流体性质与活动性集中体现了花岗岩对成矿的控制能力,即花岗岩的成矿能力。初步建立了南岭地区钨锡花岗岩的成矿矿物学研究体系。黑云母、榍石、锆石、锡石、金红石、黑钨矿、白钨矿和钨铁铌矿等是讨论的重点矿物,它们可用于判别花岗岩的成矿能力。首先以矿物晶体化学为基础,介绍了上述矿物在钨锡花岗岩中的岩相学特征、内部构造和矿物化学及其变化,并分别论证了花岗岩原始含矿性、花岗岩结晶演化和花岗岩中成矿元素活动性的矿物学标志;其次,系统对比了南岭地区三类钨锡花岗岩（准铝质含锡花岗岩、过铝质含锡花岗岩和过铝质含钨花岗岩）的成矿矿物学特征。以湖南骑田岭花岗岩复式岩体为实例,进行了芙蓉- 菜岭含锡花岗岩和新田岭含钨花岗岩的成矿矿物学对比研究。前者以黑云母、榍石为典型含锡矿物,它们在流体富集阶段,经热液蚀变作用,导致锡的淋滤和结晶富集作用;后者则以出现岩浆白钨矿和黑钨矿为特征。提出的钨锡花岗岩成矿矿物学研究体系有助于深化矿床学研究和矿床勘探工作,并将在今后工作中进一步完善。     

Significance of selective crystal entrainment and differential crystal-melt separation in petrogenesis of granites from the Tongbai orogen

Partial melting has been shown to be an important mechanism for intracrustal differentiation and granite petrogenesis. However, a series of compositional differences between granitic melt from experiments and natural granites indicate that the processes of crustal differentiation are complex. To shed light on factors that control the processes of crustal differentiation, and then the compositions of granitic magma, a combined study of petrology and geochemistry was carried out for granites (in the forms of granitic veins and parautochthonous granite) from a granulite terrane in the Tongbai orogen, China. These granites are characterized by high SiO₂ (>72 wt%) and low FeO and MgO (<4 wt%) with low Na₂O/K₂O ratios (<0.7). Minerals in these granites show variable microstructures and compositions. Phase equilibrium modelling using P–T pseudosections shows that neither anatectic melts nor fractionated melts match the compositions of the target granites, challenging the conventional paradigm that granites are the crystallized product of pure granitic melts. Based on the microstructural features of minerals in the granites, and a comparison of their compositions with crystallized minerals from anatectic melts and minerals in granulites, the minerals in these granitoids are considered to have three origins. The first is entrained garnets, which show comparable compositions with those in host granulites. The second is early crystallized mineral from melts, which include large plagioclase and K-feldspar (with high Ca contents) crystals as well as a part of biotite whose compositions can be reproduced by crystallization of the anatectic melts. The compositions of other minerals such as small grained plagioclase, K-feldspar and anorthoclase in the granites with low Ca contents are not well reconstructed, so they are considered as the third origin of crystallized products of fractionated melts. The results of mass balance calculation show that the compositions of these granites can be produced by mixing between different proportions of crystallized minerals and fractionated melts with variable amounts of entrained minerals. However, the calculated modal proportions of different crystallized minerals (plagioclase, K-feldspar, biotite and quartz) in the granites are significantly different from those predicted by melt crystallization modelling. Specifically, some rocks have lower modes of biotite and plagioclase, whereas others show lower K-feldspar modes than those produced by melt crystallization. This indicates that the crystallized minerals would be differentially separated from the primary magmas to form the evolved magmas that produce these granites. Therefore, the crystal entrainment and differential melt-crystal separation make important contributions to the composition of the target granites. Compared with leucogranites worldwide, the target granites show comparable compositions. As such, the leucogranites may form through the crystal fractionation of primary granitic magmas at different extents in addition to variable degrees of partial melting.     

The variety of lithologies in the Yamato-86032 lunar meteorite: Implications for formation processes of the lunar crust

We performed a petrologic, mineralogical, geochemical, and isotopic study of several lithologies in the Y-86032 feldspathic breccia. This study leads us to conclude that Y-86032 likely originated on the lunar farside. Y-86032 is composed of several types of feldspathic clasts, granulitic breccias, and minor basaltic clasts set in a clastic matrix. We identify an “An97 anorthosite” that has An contents similar to those of nearside FANs. Mg′ (= molar Mg/(Mg + Fe) × 100) values vary significantly from ∼45 to ∼80 covering the ranges of both nearside FANs and the Mg′ gap between FANs and the Mg-suite. A light-gray feldspathic (LG) breccia making up ∼20% of the investigated slab (5.2 × 3.6 cm²) mainly consists of fragments of anorthosites (“An93 anorthosite”) more sodic than nearside FANs. LG also contains an augite-plagioclase clast which either could be genetically related to the An93 anorthosite or to slowly-cooled basaltic magma intruded into the precursor rock. The Na-rich nature of both An93 anorthosite and this clast indicates that the LG breccia was derived from a relatively Na-rich but incompatible-element-poor source. The Mg′ variation indicates that the “An97 anorthosite” is a genomict breccia of several types of primary anorthosites. Granulitic breccias in Y-86032 have relatively high Mg′ in mafic minerals. The highest Mg′ values in mafic minerals for the “An97 anorthosite” and granulitic breccias are similar to those of Mg-rich lithologies recently described in Dhofar 489. Basaltic clasts in the dark-gray matrix are aluminous, and the zoning trends of pyroxene are similar to those of VLT or LT basalts. The crystallization of these basaltic clasts pre-date the lithification age of the clastic matrix at ∼3.8 Ga. The low K contents of plagioclase in both the anorthositic and basaltic clasts and generally low incompatible element abundances in all the lithologies in Y-86032 indicate that KREEP was not involved during the formation of the precursor lithologies. This observation further suggests that urKREEP did not exist in the source regions of these igneous lithologies. All these facts support the idea that Y-86032 was derived from a region far distant from the PKT and that the lithic clasts and fragments are indigenous to that region. An An97 anorthositic clast studied here has distinct Sm-Nd isotopic systematics from those previously found for another An97 anorthositic clast and “An93 anorthosite”, and suggests either that An97 anorthosites come from isotopically diverse sources, or that the Sm-Nd isotopic systematics of this clast were reset ∼4.3 Ga ago. These lines of geochemical, isotopic, and petrologic evidence suggest that the lunar crust is geochemically more heterogeneous than previously thought.     

Genesis of the Paleoproterozoic Rare-Metal Granites of the Katugin Massif

We studied the petrography, mineralogy, and geochemistry of the Paleoproterozoic (2.06 Ga) granites of the Katugin massif (Stanovoy suture zone), which hosts the combined rare-metal Katugin deposit. Three groups of granites were distinguished: (1) biotite (Bt) and biotite–riebeckite (Bt–Rbk) granites of the western block of the massif; (2) biotite–arfvedsonite (Bt–Arf) granites of the eastern block; and (3) arfvedsonite (Arf), aegirine–arfvedsonite (Aeg–Arf), and aegirine (Aeg) granites of the eastern block. The Bt and Bt–Rbk granites of the first group are mainly metaluminous and peraluminous rocks with rather high CaO contents and the minimum F contents among the granites described here. It was suggested that the granites of this group could be derived from a source dominated by crustal rocks with a small addition of mantle materials. These granites probably crystallized from a metaluminous–peraluminous melt with elevated CaO and moderate F contents. Melts of such compositions are least favorable for the crystallization of ore minerals. The Bt–Arf granites of the second group are mainly peralkaline and show high contents of CaO and Y and low contents of Na₂O and F. A mixed mantle–crust source was proposed for the Bt–Arf granites. The initial melt of the Bt–Arf granites could have a peralkaline composition with elevated CaO content and moderate to high F content. The Arf, Aeg–Arf, and Aeg granites of the third group are enriched in ore mineral and were classified as peralkaline granites with very low CaO contents, elevated Na2O and F contents, and usually very high contents of Zr, Hf, Nb, and Ta. Based on the geochemical and isotopic data, it was supposed that the source of the granites of the third group could be derivatives of basaltic magmas produced in an OIB-type source with a minor addition of crustal material to the magma generation zone. It was suggested that the primary melt of this granite group could be a peralkaline CaO-poor and F-rich silicic melt, which is most favorable for the crystallization of ore minerals. Based on the analysis of the geochemical characteristics of the three granite groups and their relationships within the Katugin massif, a qualitative model of its formation was proposed. According to this model, the Bt and Bt–Rbk granites of the western block crystallized first, followed by the Bt–Arf granites of the eastern block and, eventually, the Arf, Aeg–Arf, and Aeg granites enriched in ore minerals.     

Uranium and microcracks in a 1,000-meter core,Redstone, New Hampshire

The spatial distribution and mineralogical association of uranium in 30 samples of a 1,000 meter core from the Redstone (NH) Quarry were examined with fission track techniques, backscattered electron imaging, and energy dispersive X-ray spectrometry with the following results for the Conway and Mount Osceola granites: (1) Uranium occurs in microcracks sealed with siderite and/or with Ca+ RE fluorocarbonate minerals; the uranium contents of siderite and the RE fluorocarbonates are 1 to 30 ppm and 500–1,500 ppm, respectively. (2) Siderite and to a lesser extent RE fluorocarbonate minerals occur as replacement minerals of amphibole and biotite; the RE fluorocarbonates are the main alteration minerals of allanite. (3) The degree of alteration and the extent of uranium redistribution are greater in samples with major uraniferous microcracks. (4) The contents of Ca and Mn are approximately constant for siderite in sealed cracks throughout the Conway and Mount Osceola granites for the entire section penetrated by the corehole, approximately 700 meters. — From these observations, we conclude that an extensive set of fractures throughout a significant volume of the Mount Osceola and Conway granties were the conduits through which hydrothermal fluids containing CO₂, uranium, and REs circulated. Microcracks facilitated fluid-rock interactions resulting in alteration and uranium redistribution. Certain primary uraniferous accessory minerals, i.e., allanite and ilmenorutile may have been the source for at least part of the uranium and REs that now occur in secondary minerals in these granites.     

关于高岭村高岭土矿物的新认识

江西省景德镇市高岭村是世界闻名的高岭土产地,高岭石矿物的定名即渊源于此。搞清该区高岭土的成因和矿物组成,对我国粘土矿物学的研究具有一定意义。1978年我们对高岭村地区的高岭土矿物作了进一步的分析研究,获得了一些新认识,报导出来供有关方面讨论。     

Provenance evolution of collapse graben fill in the Himalaya—The Miocene to Quaternary Thakkhola-Mustang Graben (Nepal)

This study focuses on the detailed provenance evolution of young, syn- to post-orogenic extensional grabens in orogens like the Himalaya to trace the tectonic history of such late-stage basins, using the Neogene Thakkhola-Mustang Graben as a case study. The graben is situated within the Tibetan-Tethys zone and is filled with > 870 m of continental deposits of Miocene to Holocene age-. Based on logged sections within the predominantly alluvial to coarse-grained fluvial fill of the graben we investigated paleocurrent data and the petrology of sandstones and conglomerates including heavy minerals studies to interpret provenance and source areas in detail. Significant changes are recorded by slight differences in heavy mineral and pebble compositions.The sandstones can be classified as lithic greywackes, lithic arkoses and feldspathic litharenites. Sandstone, mudstone, quartzite and some granite clasts are dominant in conglomerates of the central part of the graben. Tetang Formation conglomerates of Miocene age comprise mostly clasts of Mesozoic rocks with an eastern provenance, consistent with measured paleocurrent directions. All paleocurrent data and compositional analyses of imbricated conglomerates of the Miocene–Pliocene Thakkhola Formation in the northeast of the graben suggest that clasts were derived from eastern source areas comprising mainly Mesozoic rocks whereas Paleozoic clasts of a western to northern source area predominate in the centre of the graben.Heavy mineral analysis indicates that tourmaline, staurolite, zircon, garnet and apatite constitute a significant proportion of the assemblages of all formations through time whereas epidote, andalusite, kyanite, chloritoid, hornblende, chrome-spinel, rutile and amphiboles are less common. These assemblages reflect in general stable minerals and low to high-grade metamorphic source rocks, and are principally controlled by reworking of older, passive margin sediments of the Tibetan-Tethys zone as indicated by provenance discrimination diagrams.Three successive stages in provenance evolution were recognized: (1) The Miocene Tetang Formation, characterized by higher kyanite values, corresponding to the Himalayan foreland evolution; (2) the Thakkhola Formation, characterized by granite clasts and significantly higher amounts of andalusite, indicating source area expansion and erosion of the Mustang-Mugu granites to the northwest; (3) the Upper Pleistocene/Holocene Kaligandaki Formation, bearing higher amounts of epidote/klinozoisite and ophiolite and high-pressure/low temperature detritus as indicated by chrome spinel and blue amphiboles, derived from the north-lying Indus-Tsangpo suture zone. The change in source areas from the Miocene/Pliocene to the Late Pleistocene/Holocene is interpreted as a result of the evolution from an initial stage of high-angle normal faulting and collapse basin formation to a low-angle extensional detachment basin system.     

Solubility of tin,tungsten and molybdenum oxides in felsic magmas

Saturation versus undersaturation of granitic melts in tin, tungsten and molybdenum oxides is discussed on the basis of experimental data. Results of dry and hydrothermal experiments are evaluated under the assumption of ideal solubility of Sn, W and Mo oxides in granitic melts. A conservative interpretation arrives at concentration levels of 1000 ppm SnO₂, WO₃ and MoO₃ respectively, considered as the maximum solubility of these components in granitic melts at 750°C-800 °C. Such values are never reached in natural granites unaffected by hydrothermal alteration and therefore even highly evolved granites are expected to be undersaturated in these metals. Consequently cassiterite and scheelite are neither common liquidus minerals of ore-bearing granites nor restite minerals from partial melting events.