变质岩构造置换与片层理概念的讨论

构造置换应分成形体置换和方位置换两类。形体置换是在一定尺度内新的透入性构造要素代替了旧的透入性构造要素,使后者不易识别或无法识别的置换作用;方位置换是在一定尺度内旧的透入性构造要素残存着,但其方位被改变,与新的透入性构造要素平行或近于平行的置换作用。片层理是受到不明显的形体置换和强的方位置换的层理,它具有片理的方位,层理的形体,是与片理产状一致的那一部分层理。     

Interpretation of aeromagnetic anomalies over part of Southeastern Nigeria using three-dimensional Hilbert transformation

We present the results of the application of three-dimensional Hilbert transformation to the analysis of airborne total field magnetic anomalies over part of Southeastern Nigeria. This study not only substantiates the usefulness of 3-D Hilbert transforms in the interpretation of magnetic anomaly maps but also more clearly delineates the structural pattern of the area, of study. Results from the previous study are discussed in relation to the results of previous geological and geophysical studies of the area.     

湖北凤梨山铅锌矿床的闪锌矿标型特征及其成因探讨

凤梨山铅锌矿产于中酸性岩浆岩与三叠系海相碳酸盐地层的热接触变质晕内。闪锌矿为主要的矿石矿物。其成矿作用可分为沉积成岩同生成矿期（I）、渗流热水成矿溶液改造富集成矿期（Ⅱ）和热接触变质成矿期（Ⅲ）。本文根据闪锌矿的地质产状、矿物共生组合及成矿作用的特点，对它进行了物理化和化学性质、矿物包裹体特征、硫与铅同位素地球化学的研究，并探讨了它的成因问题。     

中国东部中生代产铀火山岩的基本特征

产铀火山岩与非产铀火山岩存在岩石、岩石化学成分、微量元素及稀土元素的特征性差异;中国东部产铀火山洼地均形成于幔隆翼部重力高梯度带基底隆起构造环境,而火山洼地中铀的晚期主成矿作用,则以白垩纪拉张环境下贯入的中基性岩脉为先导,随后与之同步进行。     

新疆西准噶尔地区两类蛇绿岩中橄榄岩的矿物学研究

两类蛇绿岩中变质橄榄岩的矿物表现出的共同特征是:从二辉橄榄岩→斜辉橄榄岩→斜辉辉橄岩→纯橄岩→铬铁矿石,其橄榄石、斜方辉石和单斜辉石的Mg/(Mg+Fe)(矿物牌号)依次升高,表现出富Mg贫Fe的演化趋势;铬尖晶石的Cr/(Cr+Al)亦同时升高,表现为富Cr贫Al的演化特征。 变质橄榄岩中的矿物均是原始上地幔岩部分熔融的残余物。在部分熔融过程中,橄榄石与铬尖晶石是生成相矿物,而斜方与单斜辉石则是消失相矿物,正是通过两种辉石的不断消失,岩石才从二辉橄榄岩依次转化为纯橄岩,并造成纯橄岩与铬铁矿的紧密伴生。在此过程中,矿物成分时刻都在变化,造岩矿物向富Mg贫Fe,金属矿物向富Cr贫Al方向调整,这与实际测定结果是一致的。     

延庆、怀来地区地壳深部磁性构造与地震的研究

应用三维磁性层反演理论和方法，对延庆、怀来地区航磁资料进行了数据处理，反演计算了该区磁性基底埋深、居里等温面埋深和视磁化强度分布。揭示了延庆盆地、矾山盆地、怀来盆地、涿鹿盆地等四个相互联通盆地的磁性基底的定量特征。对该区地震发生的深部原因和地壳内不同特性块体与地震的关系进行了探讨；对该区地震分布的特点进行了研究；初步提出了该区地震的危险区划和今后的重点监测区。     

滇西澜沧变质带变质作用和变形作用的关系

滇西澜沧变质带经历了两期变质变形事件，其时代分别为５１９Ｍａ和２８０～１９０Ｍａ。早期变质变形事件（Ｍ１Ｄ１）可由销长石和石榴石变斑晶的包裹体痕迹确定，形成近Ｅ－Ｗ向的变形构造格局。晚期变质变形作用（Ｍ２Ｄ２）以形成蓝片岩相矿物组合，如以蓝门石（青铝门石）＋多硅白云母＋绿泥石＋石英等为特征，并形成近Ｎ－Ｓ向的变形构造格局．钠质问石以青铝闪石和蓝闪石为主，白云母多为３Ｔ＋２Ｍ；型多硅白云母，其ｂｏ均值在９．０４０Ａ以上；蓝片岩相变质作用的Ｐ、Ｔ条件估计分别为０．６～０．７ＧＰａ和３００℃。晚期变质变形事件经历了二个主要阶段（Ｍ２ａＤ２ａ和Ｍ２ｂＤ２ｂ），分别伴随透入性面理（Ｓ２）和褶劈理（Ｓ３）的形成，蓝门石的４０Ａｒ－３９Ａｒ定年分别为２７９Ｍａ和２１４Ｍａ；Ｍ２ｃＤ２ｃ期局部受到热的扰动，以及出现大量的膝折带或宽缓褶皱。上述变质变形演化历史代表了澜沧变质带的隆升及剥蚀过程。     

Fluid flow patterns and infiltration isograds in melilite marbles from the Bufa del Diente contact metamorphic aureole, north-east Mexico

In the inner aureole of the Bufa del Diente alkali syenite (north-east Mexico), thin calcareous argillite bands horizontally embedded in impure marbles acted as contact-metamorphic aquifers for hypersaline brines of magmatic origin. Thick-bedded marbles were largely impervious. From 180 m up to the intrusion contact, argillites were completely decarbonated, resulting in melilite + wollastonite + phlogopite + perovskite-bearing parageneses. In marbles, this assemblage is confined to a narrow 7-12-m-wide infiltration zone adjacent to the contact. Up to this distance, calcite + wollastonite + diopside + alkali feldspar + titanite was stable, indicating that the fluid evolution in these marbles was internally buffered. Brine infiltration from the metaargillite aquifer into the marbles occurred perpendicular to the marble-metaargillite boundaries and was confined to a zone 4-6 cm wide above the boundaries. This is documented by the three reactions Cc + Di = Mel + CO₂, (1) Cc + Kfs + Di + H₂O = Phl + Wo + CO₂, (2) Cc + Ttn = Prv + Wo + CO₂, (3) Melilites (Ak_32-45Gh_13-32Sm_32-40 to Ak_52-72Gh_0-1Sm_28-48) occur as rims around diopsides and become continuously thicker towards the metaargillite beds. Fluid inclusion observations suggest that the infiltrating brine was hypersaline (NaCl + KCl_cq～ 65 wt%) and that the reactions took place at the water-rich side of the H₂O-CO₂-salts immiscibility field at about 600d? C (2, 3) and 660 to 680d? C (1) at P～ 1200 bar and X_co2～ 0.02. Mass balance calculations show that the amount of brine infiltrated from the aquifer into the marble was very low and decreased continuously with increasing distance from the boundary. The maximum width of brine infiltration was about 6 cm. This confirms that brine flow was largely parallel to the aquifer, not perpendicular to it. The CO₂ produced by the decarbonation reactions probably escaped as an immiscible low-density H₂O-CO₂ fluid of X_co2≤ 0.5 into overlying marble via grain-edge flow. The metaargillite-marble boundary acted as a semipermeable membrane 6 cm in thickness keeping back the brine in the aquifer and losing the in-situ produced low-density CO₂-rich fluid.