摘要
铜陵地区中酸性侵入岩可划分为橄榄安粗岩系列和高钾钙碱性系列。前者岩石组合为辉石二长闪长岩+二长岩+石英二长岩,后者为辉长闪长岩+石英二长闪长岩+花岗闪长岩。两个系列岩石的组成矿物种类相似,但在不同岩石中的含量不同,主要造岩矿物为斜长石、辉石、角闪石、黑云母、钾长石、石英。橄榄安粗岩系列岩石中含有大量的深源包体,包括辉石堆积岩包体、角闪石堆积岩包体和角闪石辉长质堆积岩包体,主要矿物为辉石、角闪石,其次为尖晶石、斜长石、磷灰石、金云母;高钾钙碱性系列岩石中含大量的微粒闪长质包体、镁铁质石英二长闪长质包体和富云母包体,主要矿物为斜长石、角闪石、黑云母。在考虑温压计使用条件的前提下,选择合适的温压计计算了两个系列侵入岩及包体形成的温压条件。结果表明,橄榄安粗岩系列侵入岩侵位深度(4～6km)略小于高钾钙碱性系列侵入岩(6～7km),各种堆积包体形成于45～65km的深位岩浆房,微粒闪长质包体形成于12～15km的浅位岩浆房,镁铁质石英二长闪长质包体是早期侵入岩的边缘相,而富云母包体可能为地壳部分熔融的残余相。
Mesozoic intermediate-acid intrusive rocks in Tongling area can be divided into two magmatic series,namely the shoshonitic series and the high-potassium （K） calc-alkaline series.The shoshonitic series is characterized by the association of pyroxene monzodiorites （PMD）＋monzonites（Mz）＋quartz monzonites（QM）,whereas the high-potassium calc-alkaline series has the association of gabbro-diorite （GBD）＋quartz monzodiorites （QMD）＋granodiorites（GD）.Rocks of these two series have a similar mineral association composed of feldspar,pyroxene,hornblende,biotite,potassium feldspar and quartz,but the content of these minerals is different.The cumulate enclaves such as pyroxene cumulate,hornblende cumulate and hornblende gabbro in the shoshonitic series rocks are composed mainly of pyroxene and hornblende and subordinately of spinel,feldspar,apatite and phlogopite,while micro-diorite enclaves,mafic quartz monzodiorite enclaves and mica-enriched enclaves in the high-potassium calc-alkaline series are mainly comprised of feldspar,hornblende and biotite.Taking into account the preconditions for the application of thermobarometry,the authors calculated the pressure and temperature conditions for the formation of the intrusive rocks and enclaves.The calculated results of all enclaves and intrusive rocks show that their average temperatures and pressures are 1 357℃ and 1.783 GPa for pyroxene cumulate,1 228℃ and 1.430 GPa for hornblende cumulate,1 214℃ and 1.300 GPa for hornblende gabbro cumulate,889℃ and 0.413 GPa for micro-diorite enclave,887℃ and 0.114 GPa for mafic quartz monzodiorite enclaves,1 096～1 043℃ and 0.167～0.115 GPa for shoshonitic series,and 844～784℃ and 0.211～0.193 GPa for high-potassium （K） calc-alkaline series,respectively.If these pressure values are converted into the depth according to 3.3 kbar/km,their corresponding depths are 45～65 km for all cumulate enclaves,12～15 km for micro-diorite enclaves and about 4 km for mafic quartz monzodiorite enclaves,4～6 km for shoshonitic series and 6～7 km for high-potassium（K） calc-alkaline series,respectively.Combined with petrologic and geochemical studies of all enclaves and two series of intrusive rocks,the authors believe that all cumulate enclaves were derived from crystallization differentiation of the mafic magma in the deep magma chamber,the micro-diorite enclaves came from the mixing between evolved magma from the deep magma chamber and crustal partial melt in the shallow magma chamber,the mafic quartz monzodiorite enclaves might have been the marginal facies of early intrusive body,and the mica-enriched enclaves were probably relics of crustal partial melting.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2010年第3期271-288,共18页
Acta Petrologica et Mineralogica
基金
国家财政部科学专项(140102)
国家自然科学基金资助项目(49772106
40472034
40672049)
中国地质调查局项目(1212010918007
1212010818090
1212010611803
1212010711816)
关键词
中酸性侵入岩
包体
矿物化学
温压计
铜陵
intermediate-acid intrusive rocks
enclaves
mineral chemistry
thermobarometry
Tongling
