大兴安岭中生代岩浆岩及岩浆作用研究进展

大兴安岭地区位于中国雄伟版图的东北部,属于兴蒙造山带的东延部分。本区在地质历史时期曾发生过多期次、多阶段岩浆活动,其中尤以中生代岩浆活动最为强烈,分布最为广泛,与成矿关系最为密切。在总结前人资料的基础上,从构造地质背景入手结合锆石同位素测年资料探讨该区中生代岩浆岩和岩浆作用。研究本区中生代岩浆岩及其岩浆作用有助于我们还原其地质历史演化过程并掌握其地质演化发展规律,为该区科研及矿产勘查工作提供借鉴。

龙永煤田吕凤矿区煤层厚度、结构变化原因分析

本文根据地表、钻孔及煤矿井资料,对吕凤煤矿区的构造、岩浆岩特征进行了研究,分析了构造变动、岩浆岩侵入引起该区煤层厚度、结构的变化规律,对该区煤炭资源的开发具有一定的指导意义。

岩浆作用与地球深部过程

为纪念马杏垣院士诞辰一百周年而作.首先简述了地球系统科学的基本思想和指导意义.指出岩浆作用实质上是地球各层圈之间相互作用的结果,岩浆是地球各层圈之间物质和能量交换的重要载体.通过众多研究实例,重点讨论了岩浆作用的地球动力学意义:一方面,火成岩及其所携带的深源岩石包体可以当作地球深部的"探针"和"窗口";另一方面,火成岩也是大地构造事件的记录,可以用以恢复古板块构造格局,追溯大地构造演化历史.

Rock-forming mechanism of Qingshanjiao intrusion in Dongguashan copper(gold) deposit, Tongling area, Anhui province, China

Dongguashan deposit is a large porphyry-skarn copper（gold） deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional.

Origin of Early Creceouscalc-alkaline granite, Taxkorgan: Implications for evolution of Tethys evolution in central Pamir

The Pamir plateau may have been a westward continuation of Tibet plateau.Meanwhile,the Rushan-Pshart suture is correlative to the Bangong-Nujiang suture of Tibet,and the Central Pamir is the lateral equivalent of the Qiangtang Block.We present the first detailed LA-ICPMS zircon U-Pb chronology,major and trace element,and Lu-Hf isotope geochemistry of Taxkorgan two-mica monzogranite to illuminate the Tethys evolution in central Pamir.LA-ICPMS zircon U-Pb dating shows that two-mica monzogranite is emplaced in the Cretaceous(118 Ma).Its geochemical features are similar to S-type granite,with enrichment in LREEs and negative Ba,Sr,Zr and Ti anomalies.All the samples show negative zirconεHf(t)values ranging from 17.0 to 12.5(mean 14.5),corresponding to crustal Hf model(TDM2)ages of 1906 to 2169 Ma.It is inferred that these granitoids are derived from partial melting of peliticmetasedimentary rocks analogous to the Paleoproterozoic Bulunkuole Group,predominantly with muscovite schists component.Based on the petrological and geochemical data presented above,together with the regional geology,this work provides new insights that Bangong Nujiang Ocean closed in Early Cretaceous(120114 Ma).

广西富贺钟地区钨锡多金属矿的成矿规律及控矿因素分析

在不同的地质作用下每个矿区都有其自身的发展规律,通过研究广西富贺钟地区的钨锡多金属矿成矿规律及控矿因素,根据钨锡多金属矿成矿的时代和空间分布特征,发现了广西富贺钟地区的钨锡多金属矿具有相对成矿的规律。总结出构造、地层和岩浆岩这三种影响因素,均能对广西富贺钟地区的钨锡多金属矿成矿,产生不同程度的控制作用。此次研究更深层次的了解广西富贺钟地区的地质构造,为矿区有效开发提供科学依据。

Microstructure and Mineralogic Evidences of Fractional Differentiation： The Yesilova Ophiolite Example

The Yesilova ophiolite located in the Alpine zone. This work deals with differentiation mechanism of ultramafic cumulate in ophiolite. Generally, the sequence consists of gabbro and plagiogranite. The petrographic and petrolgichal properties of it show that the layering in gabbros are products of a differentiation by fractional crystallization insitu. Because it has ferrous compounds （magnetite, hematite） by means of volatiles （H2O, CO2） that evidence magma at high temperatures （〉700 ℃）. Ferrous liquids are compatible with fractional crystallization through olivine, plagioclase, clinopyroxene removal; whereas the evolved gabbros represent clinopyroxene, plagioclase cumulates from ferrous liquids with little amounts of trapped melt. Furthermore, cathodo luminesans image of zircons shows chemichal characteristic of oceanic plagiogranit （such as Fe2O3/MgO, Rb, Sr, Zr, TiO2） that these characters can be explained by fractional crystallization processes in the late stage of magma generation. Furthermore, all plagiogranites have small positive Eu anomalies indicating the significant role of plagioclase in the fractional crystallization. So, the Yesilova ophiolite ultramafic cumulates are the most probably related to crystal-liquid fractionation process of the oceanic crust of the Alpine belt. The plagiogranite is differentiation products of crystal-liquid insitu ofa mafic magma in the magma chamber.

Carboniferous slab-retreating subduction of backarc oceans:the final large-scale lateral accretion of the southern Central Asian Orogenic Belt

During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical and Sr-Nd isotopic data for a suite of volcanic and pyroclastic rocks from the Khan-Bogd area in southern Mongolia.These Carboniferous pyroclastic rocks generally have some early Paleozoic zircons,probably derived from the granitic and sedimentary rocks of the Lake Zone and the Gobi-Altai Zone to the north,indicative of a continental arc nature.In addition,they have a main zircon U-Pb age of ca.370–330 Ma,positive Hf and Nd isotopes,and mafic-intermediate arc affinity,similar to the coeval arc magmatism.Moreover,the pyroclastic rocks of the northern area have more mafic and older volcanic components with depositional time(ca.350–370 Ma;Visean and Bashkirian stages)earlier than that in the southern area(mainly ca.350–315 Ma;Serpukhovian and Bashkirian stages).Combining a preexisting northward subduction supported by the available magnetotelluric data with a slab rollback model of the main oceanic basin of the Paleo-Asian Ocean(PAO)during Carboniferous and Triassic times,we infer that the Carboniferous arc magmatism was probably derived from a backarc ocean triggered by slab rollback.Thus,the juvenile arc volcanism of Mongolia,together with other areas(e.g.,Junggar)in the southern CAOB,represented a significant lateral accretion that terminated after the Carboniferous due to a significant contraction of the PAO.