含钙铝榴石的葡萄石—绿纤石相平衡：以新疆萨尔托海蛇绿岩中变基性岩石为例

利用矿物内部一致性热力学数据，建立了在ＣａＯ－Ａｌ２Ｏ３－ＭｇＯ－ＳｉＯ２－Ｈ２Ｏ体系中含钙铝榴石的葡萄石－绿纤石变质相平衡，确立了在葡萄石－绿纤石－钙铝榴石－绿帘石－绿泥石－石英组合中出现绿纤石－钙铝榴石共生、葡萄石－绿纤石共生、葡萄石－绿帘石共生和绿泥石－绿帘石－钙铝榴石共生的ＰＴ区间及其意义。根据该相平衡计算了新疆萨尔托海蛇绿岩中变基性岩石的葡萄石－绿纤石相变质ＰＴ条件为Ｔ＝３２５℃～３３５℃，Ｐ＝０．４５～０．４７５ＧＰａ。并讨论了Ｆｅ３＋＝Ａｌ替代对于形成钙铝榴石－绿纤石共生的影响。本文的研究表明，葡萄石－绿纤石－钙铝榴石－绿帘石－绿泥石－石英共生组合是葡萄石－绿纤石相中偏高压组合，钙铝榴石－绿纤石共生与绿纤石－阳起石相一样代表着葡萄石－绿纤石相中较高压相，钙铝榴石在葡萄石－绿纤石相中是可以稳定存在的。     

The composition of back-arc basin lower crust and upper mantle in the Mariana Trough: A first report

Abstract The Mariana Trough is an active back-arc basin, with the rift propagating northward ahead of spreading. The northern part of the Trough is now rifting, with extension accommodated by combined stretching and igneous intrusion. Deep structural graben are found in a region of low heat flow, and we interpret these to manifest a low-angle normal fault system that defines the extension axis between 19°45' and 21°10'N. A single dredge haul from the deepest (∼5.5 km deep) of these graben recovered a heterogeneous suite of volcanic and plutonic crustal rocks and upper mantle peridotites, providing the first report of the deeper levels of back-arc basin lithosphere. Several lines of evidence indicate that these rocks are similar to typical back-arc basin lithosphere and are not fragments of rifted older arc lithosphere. Hornblende yielded an ⁴⁰Ar/³⁹Ar age of 1.8 ± 0.6 Ma, which is interpreted to approximate the time of crust formation. Harzburgite spinels have moderate Cr# (<40) and coexisting compositions of clinopyroxene (CPX) and plagioclase (PLAB) fall in the field of mid-ocean ridge basalt (MORB) gabbros. Crustal rocks include felsic rocks (70-80% SiO₂) and plutonic rocks that are rich in amphibole. Chemical compositions of crustal rocks show little evidence for a 'subduction component', and radiogenic isotopic compositions correspond to that expected for back-arc basin crust of the Mariana Trough. These data indicate that mechanical extension in this part of the Mariana Trough involves lithosphere that originally formed magmatically. These unique exposures of back-arc basin lithosphere call for careful study using ROVs and manned submersibles, and consideration as an ocean drilling program (ODP) drilling site.     

松树沟蛇绿岩中橄榄石位错构造及其流变学意义

在对东秦岭松树沟蛇绿岩的变质橄榄岩进行详细构造解析和显微构造研究的基础上，本文运用透射电子显微镜法着对橄榄石位错构造进行了研究。     

云南金沙江蛇绿岩的地球化学特征及其成因的初步研究

本文报道了出露于云南省德钦县白马雪山、书松、共卡及吉义独地区的金沙江蛇绿岩的地球化学特征。该蛇绿岩各岩石单元均为ＬＲＥＥ富集型。文中讨论了金沙江蛇绿岩的成因及其形成的构造环境，指出该区玄武岩的微量元素和ＲＥＥ分布可用ＮＭＯＲＢ与ＯＩＢ的混合来解释，推测形成于类似现今冰岛的扩张脊与地幔热柱重叠的构造环境     

Contrasting two types of orogen in Permo-Triassic Japan: Accretionary versus collisional

Abstract Proto-Japan originated from a continental margin of the Neoproterozoic Yangtze (South China) craton. It represents a unique Permo-Triassic tectonic setting in western Panthalassa, where two distinct types of orogenic belt occurred side by side. There was an accretionary orogen between the Yangtze craton and the Proto-Pacific (Farallon) Plate and a collisional orogen between the Sino-Korean (North China) and Yangtze cratons. This article reviews results of the latest on-land geological studies concerning Permo-Triassic tectonics in Japan and proposes a new plate tectonic interpretation as well as a paleogeographic reconstruction of this particularly unique geotectonic regime. Special emphases are given to (i) the accretion processes and products derived by collision-subduction of the Permian Akiyoshi paleoseamount and Maizuru paleo-oceanic plateau; (ii) the field occurrence of 220-Ma Sangun high-P/T schists and its implication for the exhumation process and 'tectonic sandwich' structure; (iii) the extensive development of a subhorizontal nappe of the pre-Jurassic rocks and their bearing on the orogenic edifice; and (iv) the restricted occurrence of the 250-Ma collision complex in the Hida and Oki belts and the relevant connection to the Precambrian cratons and collision suture in East Asia. The newly proposed paleogeographic reconstruction is also tested by faunal provinciality of Permo-Triassic fossils from shallow-water sediments.     

绿岩套和蛇绿岩套的区分标志

综合绿岩、蛇绿岩的有关概念、地质环境、岩石学、地球化学特征,论述蛇绿岩和绿岩之间的异同。 目前由于太古宙和显生宙地质构造研究的进展,使人们对绿岩套和蛇绿岩套的特征及其相互之间的异同性、联系性和形成环境越来越感兴趣。同时,在不同地区的地质构造研究中,对上述两种岩套在概念上和成因上存在混淆。本文将讨论这一问题。     

论造山带中超镁铁岩的成对分布

文中把俯冲-碰撞型造山带中出露的超镁铁岩分为蛇绿岩型和火山弧型两类,后者又细分为义敦型、阿拉斯加型及橄榄岩-闪长岩型等三个亚类。在同一造山带内,如果蛇绿岩与火山弧型超镁铁岩在空间上相伴分布,侵位的时间相近,则可共同组成一对超镁铁岩带。蛇绿岩代表封闭的洋盆残迹,而火山弧型岩体则来自过渡壳之下、消减带之上的地幔楔。文中还概述了造山带中成对超镁铁岩的分布、产出条件及其在造山带研究中的意义。     

新疆黄山地区蛇绿岩块的地质、地球化学特征及构造意义

黄山地区镁铁-超镁铁堆积杂岩,岩体小而分异好,岩体边部受构造作用强烈,属蛇绿岩中的堆积杂岩,过渡元素的配分曲线为较明显的“W”型。稀土元素配分曲线为LREE弱富集的平坦型。其中辉长岩单元为高钛型(TiO_2最大值为5.20％),这些均反映了堆积杂岩形成环境为洋中脊,分布于现在的位置是板块运动的结果。结合上述事实,通过沉积建造分析,该区在中石炭统曾存在沟弧盆体系。     

Ophiolites from the Mianlue Suture in the Southern Qinling and Their Relationship with the Eastern Paleotethys Evolution

The Mianlue suture extends from Derni-Nanping-Pipasi-Kangxian to the Lueyang-Mianxian area, then traverses the Bashan arcuate structure eastward to the Huashan region, and finally to the Qingshuihe area of the southern Dabie Mountains. From east to west, with a length of over 1500 km, the ophiolitic melange associations are distributed discontinuously along the suture. The rock assemblages include ophiolite, island-arc and oceanic island rock series, indicating that there existed a suture zone and a vanished paleo-ocean basin. The Mianliie paleo-ocean basin experienced its main expansion and formation process during the Carboniferous-Permian and closed totally in the Triassic. It belongs to the northern branch of the eastern paleotethys, separated from the northern margin of the Yangtze block under the paleotethys mantle dynamic system.     

Rheological Properties of Partially Molten Lherzolite

Lherzolite samples synthesized from fine-grained powders preparedfrom a natural xenolith were deformed at P = 300 MPa and 1373