金刚石钻探促进了我局钻探工程的飞跃发展──为吉林省地矿局推广小口径金刚石钻探20周年而作

吉林省地矿局自１９７４年推广小口径金刚石钻探以来，钻探效率大幅度提高，加强金刚石多工艺钻探技术，使全局钻探水平跃居地矿系统的前列，加快了吉林省地质找矿的速度。金刚石钻探技术成为我省黑色、有色、贵金属、非金属矿床的重要勘探手段。     

New high-pressure phases in BaCO<Subscript>3</Subscript>

Barium carbonate (BaCO₃) was examined in a diamond anvil cell up to a pressure of 73 GPa using an in situ angle-dispersive X-ray diffraction technique. Three new phases of BaCO₃ were observed at pressures >10 GPa. From 10 to 24 GPa, BaCO₃-IV had a post-aragonite structure with space group Pmmn. There are two molecules in a single unit cell (Z = 2) of the orthorhombic phase, which is same as the high-pressure phases of CaCO₃ and SrCO₃. The isothermal bulk modulus of BaCO₃-IV is K ₀ = 84(4) GPa, with V ₀ = 129.0(7) Å³ when K ₀′ = 4. The c axis of the unit cell parameter is less compressible than the a and b axes. The relative change in volume that accompanies the transformation between BaCO₃-III and BaCO₃-IV is ～6%. BaCO₃-V, which has an orthorhombic symmetry, was synthesized at 50 GPa. As the pressure increases, BaCO₃-V is transformed into tetragonal BaCO₃-VI. This transformation is likely to be second order, because the diffraction pattern of BaCO₃-V is similar to that of BaCO₃-VI, and some single peaks in BaCO₃-VI become doublets in BaCO₃-V. After decompression, the new high-pressure phases transform into BaCO₃-II. Our findings resolve a dispute regarding the stable high-pressure phases of BaCO₃.     

Linkam热台与热液金刚石压腔的熔体包裹体均一实验对比研究

熔体包裹体均一实验是利用熔体包裹体研究原始岩浆演化和挥发分组成的基础。目前,开展包裹体均一温度实验的设备主要为Linkam系列的高温热台,而热液金刚石压腔(HDAC)是近年来才被应用到熔体包裹体均一实验中的。文章以义兴寨金矿床石英斑岩为例,对比研究了Linkam TS1500高温热台和HDAC在熔体包裹体均一实验应用中的优劣。利用Linkam TS1500高温热台得出熔体包裹体的均一温度范围为943~1190℃,而HDAC的测试结果为780~890℃。实验研究表明:HDAC能够在加热的同时提供接近熔体捕获条件的外压,更适于开展富挥发分的高内压熔体包裹体的均一实验。实验过程中得到的熔体包裹体固相初熔温度范围,可为估算义兴寨金矿床石英斑岩原始岩浆晚期结晶的压力提供依据。     

英标和国标标贯设备试验结果相关性分析

为了在国内岩土设计中很好利用英国标准（BS）标贯设备的试验结果,对英国标准和中国标准（GB）标贯设备及试验结果进行分析,研究相关性。BS和GB标贯设备主要的区别是前者的锤垫质量大于后者,造成试验时两者锤击能量有差别,因此,获得的标贯击数不同。通过采用标贯能量分析仪,测量配置不同直径钻杆的BS和GB设备试验时的实际锤击能量,计算两者不同的实际锤击能量与理论锤击能量的能量比,利用能量比的差别分析BS与GB标贯击数的相关性,建立相关公式。分析显示,试验时BS标贯设备比GB标贯设备的锤击传递能量要小,标贯击数要大;钻杆直径为50 mm比直径为42 mm传递的锤击能量略高,标贯击数略低。通过研究,最终建立了BS与GB标贯设备试验结果的相关关系,英标标贯设备获得的数据从而能更好运用于中国标准中,并提供符合中国利用标贯评价的岩土设计参数。     

中国主要高压-超高压变质带的大地构造背景及俯冲/折返机制的探讨

造山带中发现超高压矿物柯石英和金刚石,被认为与洋壳或陆壳岩片的深俯冲(>100km)有关。但探讨这些岩片是如何俯冲和折返的？却是一个极具挑战的难题。目前,中国境内含榴辉岩的高压超高压（HP/UHP）变质带已经发现11条,此外,世界各地发现的高压超高压变质带还有至少20条。高压超高压变质带,特别是中国众多的HP-UHP变质带,在什么特定的大地构造条件中形成？又是在怎样的构造背景下折返而剥露地表？中国大陆上为什么出现众多规模可观的HP-UHP变质带？为什么出现洋壳（深）俯冲与陆壳（深）俯冲不同类型的HP-UHP带？这是本文试探讨的问题。根据中国境内的11条高压/超高压变质带形成时代和区域构造背景,将其分为4类：Ⅰ.始特提斯（早古生代）高压/超高压变质带,包括（1）柴北缘-南阿尔金超高压变质带,（2）北祁连-北阿尔金高压变质带,（3）东秦岭超高压变质带;Ⅱ.古特提斯高压/超高压变质带,包括（4）大别高压/超高压变质带,（5）苏鲁高压/超高压变质带,（6）西藏羌塘高压变质带;（7）西藏松多（超）高压变质带;Ⅲ.新特提斯高压/超高压变质带,包括（8）雅鲁藏布江东构造结南迦巴瓦（超）高压变质带;Ⅳ.古亚洲域南缘高压/超高压变质带,包括（9）新疆西南天山超高压变质带,（10）甘肃北山高压变质带,和（11）冀北高压变质带。中国高压/超高压变质带形成的大地构造背景有洋壳（深）俯冲和陆壳（深）俯冲两大成因类型,认为前者大都与始-古特提斯洋盆中微陆块之间的汇聚碰撞有关;后者为大陆块之间剪式碰撞和撕裂式岩石圈舌形板片深俯冲的产物。由于中国（邻区）大陆是三大陆块与许多小陆块聚集构成的巨大拼合体,小陆块在特提斯洋盆（特别是始、古特提斯洋盆）中的独特位置,使陆块之间的刚性洋盆岩石圈得以（深）俯冲插入小陆块之下。而大陆块之间特殊部位的碰撞为陆壳（深）俯冲创造条件。研究表明,高压/超高压变质岩石和蛇绿岩、混杂堆积、俯冲增生楔一起构成俯冲/折返杂岩带;认为代表印支造山带山根物质的大别-苏鲁高压/超高压俯冲/折返杂岩带,呈面形推覆岩片的构造样式叠置在扬子陆块之上,提出汇聚陆块边缘深部地幔物质折返的“斜向挤出”和“沿岩石圈板片的多层隧道的多重/分片挤出”的两种模式;认为走滑断裂在高压/超高压变质岩石的快速折返中起重要作用,即阿尔金走滑断裂、郯庐走滑断裂和喀喇昆仑走滑断裂,分别制约了阿尔金和祁连山中的南北两条早古生代高压/超高压变质带、大别-苏鲁印支期超高压变质带和喜马拉雅西构造结的喜山期超高压变质带的快速折返。     

Petrology,genesis and geodynamic implication of the Mesoproterozoic–Late Cretaceous Timmasamudram kimberlite cluster,Wajrakarur field,Eastern Dharwar Craton,southern India

New mineralogical and bulk-rock geochemical data for the recently recognised Mesoproterozoic(ca.1100 Ma) and late Cretaceous(ca.90 Ma) kimberlites in the Timmasamudram cluster(TKC) of the Wajrakarur kimberlite field(WKF),Eastern Dharwar Craton,southern India,are presented.On the basis of groundmass mineral chemistry(phlogopite,spinel,perovskite and clinopyroxene),bulk-rock chemistry(SiO_2.K_2O,low TiO_2.Ba/Nb and La/Sm),and perovskite Nd isotopic compositions,the TK-1(macrocrystic variety) and TK-4(Macrocrystic variety) kimberlites in this cluster are here classified as orangeites(i.e.Group Ⅱ kimberlites),with geochemical characteristics that are very similar to orangeites previously described from the Bastar Craton in central India,as well as the Kaapvaal Craton in South Africa.The remaining kimberlites(e.g.,TK-2,TK-3 and the TK-1 microcrystic variant),are more similar to other 1100 Ma,Group Ⅰ-type kimberlites of the Eastern Dharwar Craton,as well as the typical Group Ⅰkimberlites of the Kaapvaal Craton.Through the application of geochemical modelling,based on published carbonated peridotite/melt trace element partition coefficients,we show that the generation of the TKC kimberlites and the orangeites results from low degrees of partial melting of a metasomatised,carbonated peridotite.Depleted mantle(T_(DM)) Nd perovskite model ages of the 1100 Ma Timmasamudram kimberlites show that the metasornatic enrichment of their source regions are broadly similar to that of the Mesoproterozoic kimberlites of the EDC.The younger,late Cretaceous(ca.90 Ma) TK-1(macrocrystic variant)and TK-4 kimberlites,as well as the orangeites from the Bastar Craton,share similar Nd model ages of1100 Ma,consistent with a similarity in the timing of source enrichment during the amalgamation of Rodinia supercontinent.The presence of late Cretaceous diamoncliferous orangeite activity,presumably related to the location of the Marion hotspot in southern India at the time,suggests that thick Iithosphere was preserved,at least locally,up to the late Cretaceous,and was not entirely destroyed during the breakup of Gondwana,as inferred by some recent geophysical models.     

山东蒙阴金刚石的晶体形态和晶面特征

为探讨山东蒙阴金刚石的形成条件,研究了胜利Ⅰ号金伯利岩筒的金刚石晶面及晶形特征,结果认为金刚石的形成温度范围为１０００～１６００℃,压力范围为４０×１０８Ｐａ～５０×１０８Ｐａ。     

Static compression of the hydrous magnesium silicate phase D to 30 GPa at room temperature

Phase D is a dense hydrous magnesium silicate (ideal formula MgSi₂H₂O₆) which contains silicon cations exclusively in octahedral coordination. Measurements of the unit cell parameters of phase D were made to pressures of 30 GPa using a diamond anvil cell and employing synchrotron X-ray diffraction. A neon pressure medium was used. Using a third order Birch-Murnaghan equation of state the isothermal bulk modulus of phase D was determined as 166(±3) GPa with K′ equal to 4.1(±0.3). The compression of phase D is anisotropic with the c-axis twice as compressible as the a-axis. Above 20 GPa, however, the c/a ratio becomes pressure independent. Received: 29 July 1998/ Revised, accepted: 5 August 1998     

苏鲁超高压变质带中国大陆科学钻探主孔(CCSD-MH)榴辉岩中发现金刚石

苏鲁榴辉岩中除了早前发现的一粒金刚石外,最近又发现了6粒,它们具有基本相似的外形和大小,但其晶体结构与普通自然界金刚石和人工合成金刚石存在一定差别.金刚石具有异常X-射线衍射峰以及有磁铁矿的包裹体等特征,表明可以排除这些金刚石是人造或被外来样品混染的可能性.金刚石的再发现,证实苏鲁榴辉岩的形成压力可以达到4GPa以上,并且为大别和苏鲁两个超高压变质带的对比提供了一个重要标志.金刚石的异常晶胞参数和X-Ray异常峰的出现有可能与超高压变质作用有关,但需要实验岩石学研究证实.     

Aspects of diamond mineralisation and distribution at the Helam Mine, South Africa

The diamonds from the Swartruggens dyke swarm are mainly tetrahexahedra, with subsidiary octahedral and cuboid crystals. They are predominantly colourless, with subordinate yellows, browns, and greens. The existence of discrete cores and oscillatory growth structures within the diamonds, together with the recognition of harzburgite, lherzolite, at least two eclogitic and a websteritic diamond paragenesis, variable nitrogen contents, and both Type IaAB and Type Ib–IaA diamonds provides evidence for episodic diamond growth in at least six different environments. The predominance of plastic deformation in the diamonds, the state of nitrogen aggregation, and the suite of inclusion minerals recovered are all consistent with a xenocrystic origin for the diamonds, with the Type Ib–IaA diamonds being much younger than the rest. Mantle storage at a time-averaged temperature of ±1100 °C is inferred for the Type IaAB diamonds. The distribution of mantle xenocrysts of garnet and chromite within the high-grade Main kimberlite dyke compared to the low-grade Changehouse kimberlite dyke strongly suggests that the difference in diamond content is due to an increased eclogitic component of diamonds in the Main kimberlite dyke.