赞比亚铜矿床类型及地质特征

赞比亚是世界著名的铜产地之一,其铜矿类型可分为层控型、沉积型、变质改造型及热液型,以沉积型为主。据现有大中型矿床铜资源量统计,沉积型矿产铜资源量占赞比亚铜总资源量的79%。各类型铜矿床总体受卢弗里安(Luflian)弧控制,层控型铜矿主要分布在穹窿核部边缘,含矿岩系为莫瓦(Muva)超群的黑云母片岩、二云石英片岩;沉积型铜矿主要分布在背斜或穹窿外缘周围,含矿岩系主要是加丹加(Katanga)超群下部的砂页岩层。     

依兰盆地达连河组油页岩沉积特征及分布规律

依兰盆地为伸展作用下形成的半地堑式断陷盆地,油页岩发育于古近系达连河组中。油页岩与煤层伴生,分布在煤层顶部,是最主要的含矿层位。它形成于湖泊体系与沼泽体系,主要发育在水进体系域与高水位体系域中。其中,高水位体系域即上煤层顶板存在油页岩密集段,使得盆地油页岩资源潜力大幅度提高。达连河矿区是油页岩富集成矿的中心区带,东西向断裂控制着达连河组油页岩矿层的埋深以及展布成矿过程。     

Examples of convective fractionation in high‐temperature granites from the Lachlan Fold Belt

Igneous rocks derived from high‐temperature, crystal‐poor magmas of intermediate potassic composition are widespread in the central Lachlan Fold Belt, and have been assigned to the Boggy Plain Supersuite. These rocks range in composition from 45 to 78% SiO₂, with a marked paucity of examples in the range 65–70% SiO₂, the composition dominant in most other granites of the Lachlan Fold Belt. Evidence is presented from two units of the Boggy Plain Supersuite, the Boggy Plain zoned pluton and the Nallawa complex, to demonstrate that these high‐temperature magmas solidified under a regime of convective fractionation. By this process, a magma body solidified from margin to centre as the zone of solidification moved progressively inwards. High‐temperature near‐liquidus minerals with a certain proportion of trapped interstitial differentiated melt, separated from the buoyant differentiated melt during solidification. In most cases much of this differentiated melt buoyantly rose to the top of the magma chamber to form felsic sheets that overly the solidifying main magma chamber beneath. Some of these felsic tops erupted as volcanic rocks, but they mainly form extensive high‐level intrusive bodies, the largest being the granitic part of the Yeoval complex, with an area of over 200 km². Back‐mixing of fractionated melt into the main magma chamber progressively changed the composition of the main melt, resulting in highly zoned plutons. In the more felsic part of the Boggy Plain zoned pluton back‐mixing was dominant, if not exclusive, forming an intrusive body cryptically zoned from 63% SiO₂ on the margin to 72% SiO₂ in the core. It is suggested that tonalitic bodies do not generally crystallise through convective fractionation because the differentiated melt is volumetrically small and totally trapped within the interstitial space: back‐mixing is excluded and homogeneous plutons with essentially the composition of the parental melt are formed.     

Two contrasting granite types: 25 years later

The concept of I‐ and S‐type granites was introduced in 1974 to account for the observation that, apart from the most felsic rocks, the granites in the Lachlan Fold Belt have properties that generally fall into two distinct groups. This has been interpreted to result from derivation by partial melting of two kinds of source rocks, namely sedimentary and older igneous rocks. The original publication on these two granite types is reprinted and reviewed in the light of 25 years of continuing study into these granites.     

Rb‐Sr geochronology and Sr isotopic composition of Devonian granitoids,eastern Tasmania

Biotite igneous ages and well‐defined isochron ages of plutons from the composite Blue Tier Batholith and the Coles Bay area in northeastern Tasmania range from 395 to 370 Ma. The older limit of this range, for the George River granodiorite, is considerably older than any age previously recorded for NE Tasmania. The ages of the youngest plutons (Mt Paris and Anchor granites), which host cassiterite ores, record pervasive hydrothermal alteration events. The initial ⁸⁷Sr/⁸⁰Sr ratios of the granitoids range from 0.7061 to 0.7136 and suggest different protolith compositions, consistent with mineralogical and geochemical characteristics of each pluton. The S‐type garnetbiotite granites (Ansons Bay and Booby alia granites) have initial ratios greater than 0.7119, indicative of enriched, high Rb/Sr ratio, crustal source‐rocks of Proterozoic age (1700–800 Ma). The S‐type biotite granites (Poimena and Pearson granites) have relatively high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7070, 0.7105) but overlap with those of the I‐type granodiorites (George River, Scamander Tier, Pyengana and Coles Bay granodiorites) which are in the range of 0.7061 to 0.7073. The initial ratios of the enriched altered plutons are poorly constrained, and on both hand‐specimen and thin‐section scales, reveal open‐system Sr isotopic patterns.

Isochron ages for the arenite‐lutite and lutite sedimentary associations of the Mathinna Beds, which are intruded by the granitoids, reflect an approach to Sr isotopic equilibrium during regional metamorphism. The metamorphic age (401 ± 7 Ma) of the early Pragian arenite‐lutite association indicates a relatively small time interval between deposition, regional metamorphism and granitoid intrusion. The isotopic age for the lutite sedimentary association (423 ± 22 Ma) is tentatively correlated with a Benambran‐age burial metamorphic event that has not previously been recorded in Tasmania.     

辽宁西丰大岩体的解体及其地质意义

西丰大岩体在辽宁省地质上占有十分显赫的位置,一方面它出露面积巨大,另一方面与其相关的矿产比较丰富.西丰大岩体未解体之前是辽宁省最大的岩体之一,位于辽宁省的东北角,南起清河,向北延至吉林省,在辽宁省境内出露面积逾2500km2.与其相关的矿产有铁矿、铜矿、铅锌金银钼多金属矿及萤石矿.根据构造-岩浆演化期次原则,按岩石学、岩石地球化学、同位素年代学、岩体间的接触关系及岩体与地层的接触关系等,将西丰大岩体(辽宁省部分)进行了详细解体,重新归并成早二叠世、早三叠世、中侏罗世和晚白垩世4个侵入期次.其中早二叠世有3个侵入序次、早三叠世1个侵入序次、中侏罗世3个侵入序次、晚白垩世4个侵入序次,共划分为11个侵入序次.在此基础上对岩性的成矿专属性、矿床成因类型和成矿时限进行了专门研究.     

山西富东煤矿水害类型分析及其防治建议

富东煤矿主采煤层为石炭系上统太原组8、9、12、15上、15下号煤。近年来,随着开采水平的不断延伸,矿井水害日益呈现,对采掘工作面人员及安全生产构成威胁。以涌水水源与导水通道为划分原则,将整合后的富东煤矿面临的水害类型划分为采(古)空区及相邻矿井开采积水水害、含水层突水水害、断层破碎带突水水害、岩溶陷落柱水害以及地表水体突水水害,并分析了各种水害类型特点及其对煤矿安全生产的影响程度,认为在煤层开采过程中,导水裂隙带直接进入第四系松散强含水体或断层破碎带,若支护不当,雨季沟谷中的地表径流、各种含水层中地下水以及上覆煤层采空区积水都会通过断层及陷落柱等导水构造发生水力联系,对矿井造成威胁。指出了矿井水害防治重点,并提出了相应的防治水建议。     

桃山铀矿田地学信息数据库建立及成矿预测系统开发

以桃山铀矿田为例,对GIS地学信息数据库的建立及成矿预测系统的开发进行了研究,阐述了其关键技术,探讨了该数据库系统和预测系统在实际应用中的发展前景及存在的问题。     

四川省九龙县里伍铜矿矿床地球化学特征

通过对里伍铜矿地球化学特征:包裹体地球化学、稳定同位素地球化学、放射性同位素地球化学的研究,探讨里伍铜矿成矿物质来源,成矿流体来源,成矿时代,为探讨里伍铜矿成因类型和找矿提供理论依据。     

滇西茅草坪脉状铜矿床脉体构造与成矿时代研究

西南三江造山带兰坪盆地西缘发育一条重要的脉状铜矿带,通常认为其成矿与盆地演化有关,而忽略了同处于盆地西缘的崇山剪切带和成矿的关系。茅草坪是近来在该带南段新发现的一例脉状铜矿床,本文通过详细野外工作厘定矿床地质特征,重点开展露头及镜下尺度的含矿脉体构造观察,在此基础上,分选成矿期热液白云母开展40 Ar/39 Ar定年,进而探讨成矿与剪切变形的关系。研究表明,矿床热液矿物以3种形式出现:热液蚀变晕、平行剪切面理的热液脉(A1脉)、横切剪切面理的热液脉(A2脉)。以上不同脉体中的矿物不仅有连续生长的特点,而且存在一定的交切关系,反映它们大致同期形成,但矿物沉淀顺序由早到晚变化。蚀变晕形成于早期,主要由电气石和石英组成,矿物呈强定向排列,长轴平行于剪切面理,为将挤压剪切应变下形成;A1脉形成略晚于蚀变晕,主要由电气石、石英、方解石、白云石、白云母、黄铜矿等组成,矿物弱定向排列,长轴近平行于剪切面理,为弱挤压剪切应变下形成;A2脉形成最晚,脉内矿物与A1脉相似,矿物无定向性、张性充填,反映形成时剪切变形已停止,可能为变形后应力松弛阶段形成的张性脉。因此,茅草坪矿床矿化形成在剪切作用由强变弱、直至停止的过程中,为剪切作用末期的产物。A1脉体中的白云母40 Ar/39 Ar坪年龄为20.34±0.19 Ma,可以代表矿床形成年龄,表明茅草坪地区的剪切作用结束于20Ma。综上表明,茅草坪矿床形成在崇山剪切带区域剪切走滑期间(末期),矿化受与剪切变形末期相关构造控制,是一个与崇山剪切带演化有关的脉状Cu矿床。因此,兰坪盆地西缘脉状铜矿带矿床成因应充分考虑与崇山剪切带演化的关系。