粤西云炉地区混合岩的成因研究

在两广交界的云开大山加里东造山带中，从广东高州新垌向云炉方向依次发育部分混合岩化岩石、条带状混合岩、眼球条带状混合岩及片麻状混合岩等混合岩带。笔者通过对混合岩进行质量平衡计算，结构系统统计分析、矿物学、地球化学及云炉地区变质前景的研究，确定该区混合岩的主要形成机制为深溶作用。在深溶作用过程中，没有显著的钾、钠、硅等外来组分的带入和钙、铁、镁等组分的带出。     

藏南亚东混合岩的成因及地质意义

高喜马拉雅结晶岩系中广泛发育规模不等、形态各异的混合岩,是研究地壳部分熔融作用的天然实验室。尽管观察表明,藏南许多混合岩与淡色花岗岩具有一定的时空联系,但混合岩与淡色花岗岩是否具有成因联系还存在较大的争议。本文对藏南亚东地区的混合岩中进行了野外地质、岩相学、岩石地球化学和年代学等研究。研究结果表明,亚东混合岩主要是部分熔融作用的产物,具有(近)原地熔融的特征,熔融方式以白云母和黑云母脱水熔融为主,并叠加了分离结晶作用。亚东混合岩与淡色花岗岩在成因上具有紧密联系。相关认识为建立造山带构造演化模型提供新的信息。     

流体与非线性现象的成因机制研究

本文以二个典型的非线性现象（大别杂岩中的热中心混合岩和云南腾冲热海钙华中的化学振荡分层）的成因机制研究为实例，阐明了流体在成岩和成矿过程中所起的重要作用：流体不仅影响着体系能量的传递，而且，还控制着物质成分的时空分布和输运过程。流体研究是把地质过程之间耦合起来加以整体考察的关键环节。     

Geological and Geochemical Evidence for Discriminating Anatectic and Subsolidus Migmatites in the Dabieshan Complex,Northeastern Hubei Province

Based on the geological and geochemical information about migmatites,the following lines of evidence have been proposed for discriminating the anatectic leucosome in the Dabieshan Complex:(1)its width is larger than that derived from the subsolidus genesis,cutting across regional foliation,thus giving rise to complicated folds and wider selvages;(2)it is composed of melanic and accessory minerals in addition to quartz and feldspars;(3)the significant dfference in anorthites of plagioclase between paleosome and leucosome;(4)temperature and pressure(P/T) conditions revealed by the mineral compositions and assemblages are over those for the onset of anatexis;and (5)it is enriched in the major elements(e.g.Al2O3.Fe2O3and TiO2)and immobile and incompatible elements(e.g.LREE,Th,Hf and Zr).Finally,by combining the geological and geochemical features with the statistical data for the spatial distribution of minerals and mass-balance in the migatites,it is concluded that anatexis is the cardinal mechanism of migmatization in the Dabieshan Complex.     

河北阜平平阳片麻状奥长花岗岩的地质和岩相学特征

平阳片麻状奥长花岗岩位于河北阜平县平阳镇一带，围岩为包括混合岩和片麻岩在内的变质表壳岩，层位上相当于阜平群的下部，产阳地区空间上存在高级变质作用、混合岩化作用和深熔作用的“三位一体”，因而由变质岩到花岗岩显示了系统的岩石学、岩相学以及产出关系上的渐变过渡特点，花岗岩中的变质表壳岩以及部分包体不仅在岩性上可和外围的同类岩石对比，而且也显示了明显的深熔作用改造的痕迹，有较为充分的语气表明平阳片麻状花岗岩总体上是原地深熔的奥长花岗岩，局部发生了一定尺度的位移。平阳地区变质表壳岩的深熔作用经历了以流体活动占主导地位、以矿物的溶解和重结晶为主要特点的早期阶段，演变为以部分矿物的熔融占主导地位的高级阶段，平阳片麻状奥长花岗岩的形成代表了阜平岩群变质表壳岩深熔作用的高级演化阶段，对于客观认识阜平岩群的组成和地质演化具有重大意义。     

秦岭群条带状混合岩矿物空间分布的研究

由于条带状混合岩具多成因,因此,研究混合岩关键的问题之一是确定其成因。矿物空间分布特征可以用来区分混合岩的成因。本文研究表明,石英正长岩质黑云杆状混合岩其脉体、基体均为聚集分布,为分异作用形成,并同变形作用有关。用Wilcoxon秩和检验对比了花岗岩和含榴矽线黑云条带混合岩的脉体,结果表明两者的矿物空间分布一致,且趋于随机分布,这些脉体为部分熔融或注入形成。区域变质岩趋向于规则分布。组成混合岩的不同部分在矿物空间分布上可有也可以没有差异,例如,含榴矽线黑云条带混合岩中古成体同脉体有明显差异,而石英正长岩质黑云杆状混合岩基体和脉体无差异。     

冀东长城式金矿成矿中一些问题的初步探讨

长城式金矿主要受长城系岩石层间角砾岩破碎带,褐铁矿化和有机质（碳）含量控制,与岩石层位和性质无关。成矿热液可能是在伸展构造体系的控制下,超糜棱岩化变质作用衍生的变货流体或溶熔岩浆作用衍生的岩浆热液流体,在构造动力驱动下上升至盖层破碎带与天水混合的产物。它们在白云岩破碎带中渗流形成碳质含矿热液;在碎屑岩破碎带中渗流形成硅质含矿热液。     

Ultra‐high temperature metamorphism recorded in Fe‐rich olivine‐bearing migmatite from the Khondalite Belt,North China Craton

We document the first occurrence of Fe‐rich olivine‐bearing migmatitic metapelite in the Khondalite Belt, North China Craton. Petrological analyses revealed two exotic assemblages of orthopyroxene+spinel+olivine and orthopyroxene+spinel+cordierite. Phase relation modelling suggests that these assemblages are diagnostic of ultra‐high temperature (UHT) metamorphism in the Fe‐rich system, with temperatures from 1,000 to 1,050°C at 0.6 GPa. U–Th–Pb SIMS analyses on zircon reveal a similar age of c. 1.92 Ga for the olivine‐bearing migmatite and an adjacent gabbronoritic intrusion that is therefore identified as the heat source for the UHT metamorphism. These results, coupled with additional analysis of the famous Tuguiwula sapphirine‐bearing granulite, lead to a re‐appraisal of the P–T path shape and heat source for the UHT metamorphism. We suggest that UHT metamorphism, dated between 1.92 and 1.88 Ga, across the whole Khondalite belt, proceeded from a clockwise P–T evolution with an initial near‐isobaric heating path at ~0.6–0.8 GPa, and a maximum temperature of 1,050°C followed by a cooling path with minor decompression to ~0.5 GPa. Considering our results and previous works, we propose that the orogenic crust underwent partial melting at temperature reaching 850°C and depth of ~20 to ~30 km during a period of c. 30 Ma, between 1.93 and 1.90 Ga. During this time span, the partially molten crust was continuously intruded by mafic magma pulses responsible for local greater heat supply and UHT metamorphism above 1,000°C. We propose that the UHT metamorphism in the Khondalite belt is not related to an extensional post‐collisional event, but is rather syn‐orogenic and associated with mafic magma supplies.     

Multiple partial melting events in the Sulu UHP terrane: zircon U–Pb dating of granitic leucosomes within amphibolite and gneiss

Thin layers and lenses of granitic leucosome are widely distributed within amphibolites, paragneisses and orthogneisses of the Sulu UHP terrane. They are parallel to, or cross‐cut, foliations in the host rocks at different scales and show evidence of coalescence and migration to form centimetre‐ to decimetre‐scale segregations. Variously migmatized rocks extend at least 350 km from SW Sulu (Maobei) to NE Sulu (Weihai), in a band at least 50 km wide. A combined study of mineral inclusions, cathoduluminescence (CL) images, U–Pb LA‐ICP‐MS dates, and in‐situ trace element compositions of zircon provide clear evidence on the nature and timing of partial melting in these UHP rocks. Most zircon from the granitic leucosomes occurs as distinct overgrowths around inherited (igneous or metamorphic) cores or as new, euhedral crystals. The overgrowths and new crystals commonly show perfectly euhedral shapes, have pronounced oscillatory zoning and contain felsic mineral inclusions, such as Kfs + Pl + Qtz ± Ilm ± monazite (Mon). In contrast, the inherited igneous or metamorphic cores are rounded or irregular, contain low‐P or UHP mineral inclusions and show clear dissolution textures. These data suggest that the new zircon is anatectic in origin and that it grew during partial melting of the UHP rocks. The REE patterns of the anatectic zircon show steep slopes from the HREE to LREE with strongly to moderately negative Eu anomalies (Eu/Eu* = 0.31–0.72) and pronounced positive Ce anomalies (Ce/Ce* = 6.8–26.5). Abundant U–Pb spot analyses of the anatectic zircon reveal two discrete and meaningful ages of partial melting within the Sulu UHP terrane. Anatectic zircon from 12 granitic leucosomes within amphibolites, paragneisses, and orthogneisses from Sulu UHP slices II and III yields consistent mean U–Pb ages of 219.0 ± 1.2 to 218.3 ± 1.6 Ma, 218.8 ± 2.0 to 217.3 ± 1.7 Ma and 218.2 ± 1.4 to 215.0 ± 1.5 Ma, respectively. In contrast, anatectic zircon from six granitic leucosomes within paragneisses and orthogneisses from Sulu UHP slice III records younger mean U–Pb ages of 151.9 ± 1.3 to 151.1 ± 1.8 Ma and 155.9 ± 1.8 to 153.7 ± 1.7 Ma, respectively. These data imply that the Sulu UHP terrane experienced two Mesozoic partial melting events. The first partial melting event (219–215 Ma) was probably associated with a Late Triassic granulite facies stage of ‘hot’ exhumation, whereas the second (156–151 Ma) is interpreted as the result of Middle‐Late Jurassic extension and thinning of the previously thickened crust of the Sulu UHP terrane. Both partial melting events induced extensive retrograde metamorphism of the eclogites and their country rocks.