Magmatic evolution of the Løkken SSZ Ophiolite,Norwegian Caledonides: Relationships between anomalous lavas and high-level intrusions

The Lower Ordovician Løkken ophiolite fragment shows a tripartite subdivision of its thick volcanic sequence into: (1) an Upper Volcanic Member (UVM) of transitional MORB/IAT character, comprising basalts or, in a related, thrust-bounded sequence, a bimodal basalt-rhyolite assemblage; (2) a Middle Volcanic Member (MVM) derived from widely variable, generally MORB-related magmas; and (3) a Lower Volcanic Member (LVM) of N-type MORB basalts which locally passes into an underlying sheeted dyke complex. The UVM and LVM were fed from relatively deep-seated magma chambers, and lavas were erupted at moderate flow rates to form predominantly pillow lavas. The whole sequence is interpreted as having formed in a marginal basin setting. The MVM is characterized by abundant voluminous sheet basalts thought to have been erupted at high flow rates. The volcanites had their source, through extensive dyke swarms, in high-level magmas which intruded the sheeted dyke complex and parts of the LVM, possibly in a near-axial seamount setting. The magmas differentiated to form plagiogranitic melts, with a wide range of conjunctive, mafic to intermediate cumulates. This plutonic assemblage, possibly in crystal mush form, was subsequently intruded by new, mafic magma, leading partly to large-scale remelting or assimilation of cumulus phases. These processes are reflected in the MVM by common hybrid flows, as well as local intermediate lavas having the geochemical characteristics of cumulates, erupted during a period of intense faulting. Major tapping of the primary, mafic magma occurred toward the end of the period of MVM volcanism. A predominance of voluminous, apparently fluid, massive flows in the MVM is mainly ascribed to the shallow depth of magma reservoirs.     

东天山博格达造山带石炭纪火山岩及其形成地质环境

东天山博格达造山带早、中石炭世海相火山地具有双峰式特征,主要岩性为富钠的玄武岩和流纹岩,其次是英安岩,安山质岩石极少出现。玄武岩的特征是：少数岩石含有实际矿物石英,个别岩石含橄榄石斑晶;辉石主要是透辉石和次透辉石,其成分富含铝（Ａｌ２Ｏ３＝４．１７～５．９９）和钛（ＴｉＯ２＝２．８０～４．７８）;基质中的长石主要是钠－更长石,斑晶中有相当数量的中长石和拉长石;全岩化学成分ＣＩＰＷ计算结果绝大部分含     

与陆相火山作用有关的稀有金属矿化

与陆相火山作用有关的稀有金属矿床可划分为三种类型,即含稀有金属火山岩矿床,火山期后热液矿床和火山岩风化矿床。从火山岩浆作用、火山构造及围岩地层成矿条件,初步探讨了内生成矿控制因素,并指出火山岩型稀有稀土矿床在我国具有找矿前景。