10.6～1.5GPa、室温～1 200℃条件下青藏高原地壳岩石弹性波速特征

通过对采自青藏高原的六种地壳岩石，包括花岗闪长岩、混合岩、片麻岩、玄武岩、辉橄岩及斜长角闪岩等，进行高温高压纵波速度测量，发现绝大多数地壳岩石其纵波速度在压力高于0.2-0.3GPa时基本上随压力线性增加。在固定压力下随温度升高而降低，但在温度较低时这一现象并不明显，随温度的程式高波速出现明显降低。通过对实验后的样品进行显微薄片分析，发现含水矿物的脱水和部分熔融是造成岩石波迅速降低的主要原因。在实验过程中还发现高压下温度较高时，接收到的超声波振幅会增大。对实验中发现的这些现象本文进行了初步的分析和讨论。     

勘察加岛弧岩浆岩研究进展

西太平洋分布了全球大部分的洋内俯冲带,也是全球沟-弧-盆体系最发育的地区。勘察加(Kamchatka)半岛位于俄罗斯远东地区,地处太平洋西北部(51°~60°N、155°~164°E),是全球环太平洋岛弧的重要组成部分。前人对勘察加岛弧岩石地幔源区性质、熔融过程、岩浆结晶分异及熔/流体交代过程进行了详细的研究,并获得了丰硕的成果。最新的研究进展表明:(1)勘察加岛弧前缘火山和中部火山的源区主要为亏损地幔,而弧后区域则存在较为富集的地幔贡献;(2)勘察加岛弧不同区域的地幔源区流体性质具有一定的差异,导致从前缘火山至中部火山,地幔熔融程度逐渐降低;(3)勘察加岛弧不同区域岩石地球化学成分存在差异,而且,沿穿弧剖面某些元素或同位素(如δ11 B)表现出系统变化的特征,反应了俯冲板片流体通量和流体性质的差异;(4)勘察加半岛部分多期次火山(如Klyuchevskoy火山)地球化学成分复杂,可能反应了源区熔融条件的不同和岩浆结晶分异过程;(5)勘察加岛弧北部与阿留申岛弧近直角相交,导致异常的构造背景,促使该区域形成了具有埃达克质特征的岛弧岩浆。     

Melt-producing and melt-consuming reactions in the Achankovil cordierite gneisses, South India

Migmatitic cordierite gneisses within the Achankovil Zone (AZ) of southern Pan‐African India record melt‐producing and subsequent melt‐consuming mineral reactions. Early mineral assemblages Bt‐Sil‐Qtz and Bt‐Sil‐Spl, deduced from inclusion textures in garnet prophyroblasts, break down via successive dehydration melting reactions to high‐T phase assemblages (e.g. Grt‐Crd‐Liq, Opx‐Liq, Spl‐Crd‐Liq). Later back reactions between the restite and the in situ crystallizing melt resulted in thin cordierite coronas separating garnet from the leucosome, and partial resorption of garnet to Opx‐Crd or Crd‐Bt‐Qtz symplectites. Leucosomes generally display a moderate (low‐strain gneisses) to strong (high‐strain gneisses) depletion of alkali feldspar attributed to mineral‐melt back reactions partly controlled by the degree of melt segregation. Using a KFMASH partial petrogenetic grid that includes a melt phase, and qualitative pseudosections for microdomains of high and low Al/Si ratios, the successive phase assemblages and reaction textures are interpreted in terms of a clockwise P–T path culminating at about 6–7 kbar and 900–950 °C. This P–T path is consistent with, but more detailed than published results, which suggests that taking a melt phase into account is not only a valid, but also a useful approach. Comparing P–T data and lithological and isotopic data for the AZ with adjacent East Gondwana fragments, suggests the presence of a coherent metasedimentary unit exposed from southern Madagascar via South India (AZ) and Sri Lanka (Wanni Complex) to the Lützow–Holm Bay in Eastern Antarctica.     

尖晶石在地幔橄榄岩部分熔融和亚固相平衡过程中的化学指示——实验研究及在自然岩石中的应用

以三组不同的重组的尖晶石橄榄岩为起始成分.在压力为0.10—0.15GPa和温度为1000—1380℃条件下,进行了系统的部分熔融和亚固相平衡实验。实验结果显示,在部分熔融过程中,尖晶石的Mg＃,即Mg/(Mg+Fe),和Cr＃,即Cr/(Cr+Al),随熔融度的增大而增大;在亚固相平衡过程中,尖晶石的Mg＃随温度的升高而增大,但Cr＃在纯橄榄岩中保持不变,而在二辉和方辉橄榄岩中稍有增大。尖晶石的Mg＃—Cr＃间反相近线性代表了一种非整体平衡的等热关系。计算模拟得到同样的结果。这同时被自然橄榄岩中尖晶石的Mg＃—Cr＃间的关系所证明。由于亚固相条件下平衡的结果,尖晶石的化学成分中只有Cr＃变化不大,故能用来衡量其所在岩体曾经受的相对熔融度。即尖晶石的Cr＃越大,所在岩体经受的熔融度越大。相反,尖晶石的Mg＃和Cr＃在岩浆结晶过程中应随温度的降低而减小;因此,可用玄武岩中尖晶石的Cr＃来指示其岩浆的原始Cr_2O_3/Al_2O_3特征,及用尖晶石的环带特征来探讨岩浆的演化(冷却速度,混染情况)。     

Feinauflösung von UV-Spektren durch Differentiation 1. und 2. Ordnung im Rahmen der Kohlenwasserstoffanalyse

Fine Resolution of UV Spectra by Differentiation of 1st and 2nd Order in Hydrocarbon Analysis Basic UV spectra (0th order) in unpolar solvents such as cyclohexane are useful — though with some reservations — in characterizing mineral oils occuring in pure form and aromatic fractions in environmental samples separated by chromatographic techniques. The common standard raffinates, biogenic hydrocarbons or other mixes of hydrocarbons including polycyclic aromatics can be approximately identified. The spectra of 1st and 2nd order improve the reliability of the results and permit above all to detect polycondensated aromatics even in traces. Finally, partial spectra of 1st and 2nd order in the wavelength ranges 205…240, 220…260, and 260…320 nm allow because of their very specific structures a simple and fast practically definite assignment to the above-mentioned groups of aromatics. Analogously, substituted aromatics in detergents and other technical products have already been identified. The method is suitable as a fast preliminary test, at least.     

Extreme heterogeneity in sr isotope systematic in the himalayan leucogranites: A possible mechanism of partial melting based on thermal modeling

The small leucogranite plutons occurring in linear belts in the Higher Himalayas have formed due to post-collision partial melting within the Himalayan crust. Several studies have documented that the Sr isotopic ratios in the granite bodies show chaotic variation and meaningful Rb-Sr isochron ages are difficult, if not impossible, to obtain. In tectonically overthickened crust, the depth-temperature profile (geotherm) remains strongly transient for the first tens of millions of years. It is proposed here that the intersecting relations between the transient geotherms and activity-dependent solidus/melting curves may generate small pods of magma at different depths and at different times. Each of these pods will have its unique Sr isotopic ratios. Coalescence of these small pods of magma without any effective homogenization due to deformation-induced fast segregation, ascent and emplacement may lead to pluton-wide extreme heterogeneity in Sr isotopic ratios.     

A method for modelling mass balance in partial melting and anatectic leucosome segregation

A method is proposed for adjusting the mass balance to characterize quantitatively the behaviour of minerals in anatexis. The method is based on an unconstrained simple mixing model that can be expressed as: where B , A ₀, and A _1-n, are compositional vectors of segregate, source rock and source minerals, respectively. The most important concepts are: (1) degree of partial fusion: F^MM= 1/a₀; (2) mineral fractionation index: and (3) plagioclase differentiation index: . For a given mineral, the MFI values have the following meaning: (a) MFI <0: residual phase originated, at least partly, as a product of incongruent melting; (b) 0 > MFI <1: preferential retention in the residue; (c) MFI= 1: identical modal fraction in source and melt; (d) a₀ > MFI > 1: preferential incorporation into the segregate, and (e) MFI > a₀: external contribution to the anatectic system defined by a₀ A ₀. To test the method and illustrate its use, it was applied to two real problems of partial melting in the Peña Negra Anatectic Complex (Central Spain). The first is a very simple case of segregation of a diktyonitic neosome from an orthogneiss through partial melting located in vertical shear zones. This process is characterized by: (1) F^MM= 0.51; (2) active incorporation of K-feldspar, plagioclase and biotite into the segregate; (3) disequilibrium melting of plagioclase; (4) residual behaviour of quartz and ilmenite. The second case concerns the formation of a cordierite-bearing granite from granodioritoid diatexites through an anatectic process, whose most salient characteristics are: (1) F^MM= 0.45; (2) incongruent melting of biotite; (3) residual behaviour of plagioclase, which melted with a PDI of 1.22; (4) preferential incorporation of quartz into the segregate; (5) total extraction of K-feldspar from the residue.     

华北地块南缘太古宙灰色片麻岩及其成因

华北地块南缘太古宙登封花岗-绿岩地体和太华高级片麻岩地体中的英云闪长-奥氏花岗质和花岗闪长质灰色片麻岩多占据背斜核部或穹窿部位,它们是多期侵入的复合岩体。灰色片麻岩与表壳岩中的拉斑玄武岩构成双峰式岩套,属高Al_2O_3型,随岩浆演化,表现了Na_2O/K_2O,K/Rb比值逐渐降低,Rb/Sr比值升高的地球化学趋势,其LREE富集,HREE亏损U(Ce/Yb)_N=10—25]和Eu呈正异常。经模拟计算,登封灰色片麻岩是由石英榴辉岩约10—35％部分熔融形成,而石英榴辉岩系绿岩带中拉斑玄武岩的转变产物。太华灰色片麻岩可能由富含REE的母岩的部分熔融形成。     

辽南地壳韧性剪切变形中的分形及自组织

本文在研究了辽南地壳的韧性剪切变形特征的基础上，详细研究了发育于韧性剪切带中的剪切褶皱、韵律变质分异层理、Ｓ－Ｃ组构、不对称旋转碎斑系及石英动态重结晶颗粒的大小分布及其边界的分形特征和自组织现象。给出了石英动态重结晶颗粒的大小分布及其边界的分形维数，探讨了韵律变质分异层理和剪切生热的成因关系。