The dolomite-dissociation textures documented here in rocks from the Kokchetav ultrahigh-pressure massif suggest that the experimentally expected dolomite dissociation happened in the subducted slabs represented by these rocks. Two reactions, magnesite=C + MgO + O2, and majoritic garnet + MgO + H2O = garnet + clinochlore, recorded in carbonate inclusions and the host majoritic garnet are responsible for generation of graphite and clinochlore during the exhumation. The dolomite dissociation indicates that carbonate materials were subducted to depths of .250 km below Earth’s surface. Such deep subduction evidently brings abundant carbon and carbonate into deep Earth.

The Wangfeng–Tianger–Saridala ore district consists of over 20 orebodies with total proven gold reserves exceeding 15 tonnes. The district is located on the EW-striking Tianger (Bingdaban) shear zone in west Tianshan Mountains, northwest China. The lensoid orebodies are distributed along the shear zone in a region about 25 km in length and 1 km in width. Enhanced fluid flow and fracturing controlled location and orientation of mineralized zones during deformation along narrow shear bands oriented oblique to the overall shear zone margins. Fabrics in fractures and strain shadow overgrowths generally plunge steeply, parallel to the lineation in the surrounding cataclasite matrix consisting of new grains of quartz and minor amounts of micas. Native gold occurs inmylonitized granites ormylonitized sulfide–mica–quartz veins.Gold grade is closely relatedwith the occurrence of sulfide–quartz veins. Pyrite and pyrrhotite in gold-bearing sulfide–quartz veins contain inclusions of native gold. Chondrite-normalized rare earth element (REE) distribution patterns for pyrite from the orebodies show light REE enrichments and negative Eu anomalies. Relationships between gold contents and Th/U, Zr/Hf and (La/Yb)N values for pyrites imply that gold-rich pyrites are different from goldpoor pyrites, thus indicate that the pyrites in the orebodies have a different origin compared with those in wall rocks. A Rb–Sr isochron for the mylonitized Au-bearing quartz veins indicates an age of 224±14 Ma with an initial 87Sr/86Sr ratio of 0.7294±0.0089 (MSWD=1.1). This age is conformed by 40Ar/39Ar dating on muscovites (220.9 to 222.5Ma), which is interpreted as the age of ore-formation in the Tianger deposit. High initial 87Sr/86Sr ratios (0.7294), high δ34S values (+11.2 to +16.5‰), low δ18OH2O values (1.67 to 3.07‰) and low δD values (−84 to −104‰) indicate that the ore-forming fluid was unrelated to any magmatic process. © 2006 Elsevier B.V. All rights reserved.

中国东部苏鲁地区江苏赣榆出露大理岩-榴辉岩块体，其菱镁矿大理岩中保存的白云石分解结构表明地壳物质俯冲深度达到-200公里。在与该大理岩共生的榴辉岩中，我们发现了磷灰石的磁黄铁矿出溶结构。磷灰石是该榴辉岩的主要副矿物，其自形程度较高，与石榴石共生。样品中几乎所有磷灰石均发育出溶结构，至少存在两组相互垂直的出溶棒，它们各自严格沿同一个方向分布。出溶棒形状规则，宽度相近(1µm)，但长度变化大(5～50µm)。利用高分辨能谱仪测定其能谱，结果表明，出溶棒主要同Fe和S两种元素组成，但不能准确地确定其Fe/S比值。我们把这种出溶棒初步确定为磁黄铁矿(Fe1-x S)。磷灰石由于含大量稀土元素和挥发性组分如OH、F、Cl等以及我们所观察到的S，它的深循环因此可能对地球的水、硫以及其它挥发性组分的全球平衡具有重要影响。本文报道的磷灰石中磁黄铁矿出溶结构为深入探讨这个基本科学问题提供了一个新的突破口。

Clinopyroxene phenocrysts in the Kokchetav trachybasalts are variable in composition and textures. Two distinctive cores are recognized: diopside cores and green salite cores. The diopside cores with Mg# of 80–90 are mantled by colorless salite rims with Mg# of 70–80. The green salite cores have especially low Mg# (<70) but high Al and Ti contents. A Mg-rich band (Mg# = 82–90) usually occurs between a green salite core and its rim, and/or between a colorless salite mantle and its rim. Dissolution surfaces are observed on all textural variants. Two magma chambers are needed to explain the observed clinopyroxene phenocrysts. A deep chamber at about 120 km in the upper mantle in which diopside cores crystallized, and a shallow chamber at depths of less than 40 km in which diopside cores were resorbed and overgrown by salite rims or mantles. Magma mixing in the shallow chamber is responsible for the formation of dissolution surfaces between the diopside bands and the colorless salite mantles. The dissolution surfaces on the diopside cores formed in the shallow chamber as a result of pressure decrease. This magma evolution scenario is complicated by the occurrence of the crustal-origin green salite cores in diopsides. These green cores likely represent the relics of continental materials, which were captured in the deep chamber and partially re-melted. Our observations indicate that subducted continental materials were returned to the Earth’s surface as a result of magmatism. This study therefore provides direct evidence of a link between subducted continental materials (slab) and magmatism in this orogenic belt. © 2003 Elsevier Ltd. All rights reserved.