桑托斯盆地L构造Aptian期火山喷发旋回特征与Itapema组介壳灰岩沉积     

赵健  赵俊峰  任康绪  王红平  王朝锋  阳孝法  杨柳 《地质学报》2023,97(2):539-552

桑托斯盆地裂陷初期岩浆活动与储层发育关系密切。本文以盆地L区块火成岩-介壳灰岩复合体为研究对象,通过对火成岩岩石学、年代学测试及钻井、测井资料分析等,首次明确了桑托斯盆地裂陷初期岩浆活动特征及其对介壳灰岩沉积过程的控制,并指出介壳灰岩储层的分布特征。L区块内火成岩分属晚白垩世Santonian期—Campanian期和早白垩世Aptian两期岩浆活动产物,并以Aptian期为主,至少经历了7次不连续喷发和3次侵入过程,形成了块状玄武岩、杏仁状玄武岩和玻基斑状玄武岩(含再沉积玻基斑状玄武岩)等喷发相火成岩和以辉绿岩(局部属粗玄岩)、煌斑岩形式产出的侵入相火成岩。Aptian期岩浆多期活动重塑了古地貌,形成了局部构造凸起,促成并控制了下白垩统Itapema组至少6期介壳灰岩沉积,最终形成了～620 m厚火成岩-介壳灰岩复合体。介壳灰岩储层呈透镜体形状,以“散点式”不连续分布在Aptian期盆内古隆、古断阶(坡)等区域,横向连续性差,垂向连通性受限,其发育规模和质量受古地貌及水深条件等影响。  相似文献   

准噶尔盆地玛湖凹陷风城组页岩自生长英质矿物的成因机理及其储层改造意义     

郭佩  柏淑英  李长志  雷海艳  徐文礼  张锡婷  文华国 《地质学报》2023,97(7):2311-2331

玛湖凹陷二叠系风城组是近几年准噶尔盆地页岩油接替的主攻领域,但其页岩成岩改造强烈,原始岩性归属尚不明确。X射线粉晶衍射测得风城组页岩黏土矿物含量普遍较低（<10%）,长英质矿物含量较高（60%~80%）。薄片分析发现风城组长英质页岩存在三种类型：① 粉砂级（4~63 μm）长石和石英碎屑含量丰富,为典型的粉砂岩;② 燧石条带和团块发育,为富硅页岩;③ 长英质基质发育,呈非碎屑状,且火山尘及火山玻璃少见,其矿物组成和形态与典型的黏土岩、粉砂岩及沉凝灰岩明显不同。背散射图像和高精度扫描电镜测得该长英质基质由碎屑和自生石英、钾长石和钠长石共同组成,可见黏土矿物、碎屑钾长石和钠长石向自生石英转化,碎屑钾长石向自生钠长石转化。通过调研全球中新生代碱湖沉积中自生硅酸盐矿物组合特征和成岩演化规律,探讨了二叠系风城组“贫”黏土矿物和“富”自生长英质矿物的原因,并提出风城组发育一类“改造长英质页岩”,主要由原始黏土和长石碎屑矿物和火山物质经过多期成岩改造而成。早期高碱（pH>9）沉积和成岩环境增加了SiO2溶解度和元素铝的活性,导致黏土矿物、泥级—细粉砂级长英质碎屑、火山灰等在入湖后发生“溶解、转化”,形成次稳定的硅酸盐矿物,如沸石和含镁蒙皂石,在经历漫长埋藏成岩后进一步转化为更为稳定的石英、钾长石和钠长石。碱湖页岩的成岩改造过程消耗了黏土矿物和火山灰,极大增加了页岩脆性,同时伴生了大量基质溶孔和晶间孔,是一类优质的页岩储层。  相似文献   

PETROLOGY 1.IGNEOUS PETROLOGY     

《Abstract of Chinese Geological Literature》2014,(2)

正20140707Bai Yunshan(Wuhan Center,China Geological Survey,Wuhan 430205,China);Duan Qifa Geological Characteristics and Tectonic Significance of Volcanic Rocks from Kenan Formation of the Upper Triassic in Zhahe Area,Southern Qinghai Province(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(2),  相似文献   

Episodic granite accumulation and extraction from the mid‐crust          下载免费PDF全文

D. Hall  A. Kisters 《Journal of Metamorphic Geology》2016,34(5):483-500

The processes of long‐range granitic magma transfer from mid‐ and lower crustal anatectic zones to upper crustal pluton emplacement sites remain controversial in the literature. This is partly because feeder networks that could have accommodated this large‐scale magma transport remain elusive in the field. Existing granite ascent models are based largely on numerical and theoretical studies that seek to demonstrate the viability of fracture‐controlled magma transport through dykes or self‐propagating hydrofractures. In most cases, the models present very little supporting field evidence, such as sufficiently voluminous near‐ or within‐source magma accumulations, to support their basic premises. We document large (deca‐ to hectometre‐scale), steeply dipping and largely homogeneous granite lenses in suprasolidus (~5 kbar, ~750 °C) mid‐crustal rocks in the Damara Belt in Namibia. The lenses are surrounded by and connected to shallowly dipping networks of stromatic leucogranites in the well‐layered gneisses of the deeply incised Husab Gorge. The outcrops define a four‐stage process from (i) the initial formation and growth of large, subvertical magma‐filled lenses as extension fractures developed at high angles to the subhorizontal regional extension in relatively competent wall‐rock layers. This stage is followed by (ii) the simultaneous lateral inflation and (iii) subcritical vertical growth of the lenses to a critical length that (iv) promotes fracture destabilization, buoyancy‐driven upward fracture mobilization and, consequently, vertical magma transport. These field observations are compared with existing numerical models and are used to constrain, by referring to the dimensions of the largest preserved inflated leucogranite lens, an estimate of the minimum fracture length (~100 m) and volume (~2.4 × 10⁵ m³) required to initiate buoyancy‐driven brittle fracture propagation in this particular mid‐crustal section. The critical values and field relationships compare favourably with theoretical models of magma ascent along vertical self‐propagating hydrofractures which close at their tails during propagation. This process leaves behind subtle wake‐like structures and thin leucogranite trails that mark the path of magma ascent. Reutilization of such conduits by repeated inflation and drainage is consistent with the episodic accumulation and removal of magma from the mid‐crust and is reflected in the sheeted nature of many upper crustal granitoid plutons.  相似文献   

Lower crustal melting via magma underplating: Elemental and Sr–Nd–Pb isotopic constraints from late Mesozoic intermediate–felsic volcanic rocks in the northeastern North China Block     

CHAOWEN LI  FENG GUO  WEIMING FAN 《Island Arc》2011,20(4):477-499

Ar–Ar dating, major and trace element analyses, and Sr–Nd–Pb isotope results of two groups of Lower Cretaceous (erupted at 126 and 119 Ma, respectively) intermediate–felsic lava from the northeastern North China Block (NCB) suggest their derivation from melting of mixtures between the heterogeneous lower crust and underplated basalts. Both groups exhibit high‐K calc‐alkaline to shoshonitic affinities, characterized by light rare earth element (LREE) and large ion lithophile element (LILE) enrichment and variable high field strength element (HFSE, e.g. Nb, Ta and Ti) depletion, and moderately radiogenic Sr and unradiogenic Nd and Pb isotopic compositions. Compared with Group 2, Group 1 rocks have relatively higher K₂O and Al₂O₃/(CaO + K₂O + Na₂O) in molar ratio, higher HFSE concentrations and lower Nb/Ta ratios, and higher Sr–Nd–Pb isotope ratios. Group 1 rocks were derived from a mixture of an enriched mantle‐derived magma and a lower crust that has developed radiogenic Sr and unradiogenic Nd and Pb isotopic compositions, whereas the Group 2 magmas were melts of another mixture between the same mantle‐derived component and another type of lower crust having even lower Sr, Nd, and Pb isotopic ratios. Shift in source region from Group 1 to Group 2 coincided with a change in melting conditions: hydrous melting of both the underplated basalt and the lower crust produced the earlier high‐Nb and low‐Nb/Ta melts with little or no residual Ti‐rich phases; while the younger low‐Nb and high‐Nb/Ta magmas were melted under a water‐deficient system, in which Ti‐rich phases were retained in the source. Generation of the two groups of intermediate–felsic volcanic rocks was genetically linked with the contemporaneous magma underplating event as a result of lithospheric thinning in the eastern NCB.  相似文献   

Petrogenetic modeling of rock variety in the Khalkhab–Neshveh pluton,NW of Saveh,Iran     

MEHDI REZAEI‐KAHKHAEI  DARIUSH ESMAEILY  FERNANDO CORFU 《Island Arc》2011,20(3):329-345

The Khalkhab–Neshveh (KN) pluton is a part of Urumieh–Dokhtar Magmatic Arc and was intruded into a covering of basalt and andesite of Eocene to early Miocene age. It is a medium to high‐K, metaluminous and I‐type pluton ranging in composition from quartz monzogabbro, through quartz monzodiorite, granodiorite, and granite. The KN rocks show subtle differentiation trends strongly controlled by clinopyroxene, plagioclase, hornblende, apatite, and titanite, where most major elements (except K₂O) are negatively correlated with SiO₂; and Al₂O₃, Na₂O, Sr, Eu, and Y define curvilinear trends. Considering three processes of magmatic differentiation including mixing and/or mingling between basaltic and dacitic magmas, gravitational fractional crystallization and in situ crystallization revealed that the latter is the most likely process for the evolution of KN magma. This is supported by the occurrence of all rock types at the same level, the lack of mafic enclaves in the granitoid rocks, the curvilinear trends of Na₂O, Sr, and Eu, and the constant ratios of (⁸⁷Sr/⁸⁶Sr)_i from quartz monzodiorite to granite (0.70475 and 0.70471, respectively). In situ crystallization took place via accumulation of plagioclase and clinopyroxene phenocrysts and concentration of these phases in the quartz monzogabbro and quartz monzodiorite at the margins of the intrusion at T ≥ 1050°C, and by filter pressing and fractionation of hornblende, plagioclase, and later biotite in the granitoids at T = ～880°C.  相似文献   

Petrochemistry of subvolcanic dike swarms associated with the Golden Revenue Au–Cu and the Stoddart Mo–Cu ± W mineralizations (Dawson Range, Yukon Territory, Canada) and implications for ore genesis     

Thierry Bineli Betsi  David Lentz 《Ore Geology Reviews》2011,39(3):134-163

  相似文献   

西藏甲玛铜多金属矿区成矿斑岩的岩浆混合作用:石英及长石斑晶新证据   总被引：6，自引：3，他引：3  

彭惠娟  汪雄武  Müller Axel  秦志鹏  侯林  周云 《矿床地质》2011,30(2):249-265

西藏甲玛矿区斑岩内石英和长石斑晶的阴极发光(CL)特征及元素含量变化有效记录了岩浆演化、混合及补给事件.石英斑晶的显微生长结构表明,原始岩浆经历过2次铁镁质岩浆混合作用.根据石英斑晶中Ti含量的变化可知,在2次溶蚀前后,石英结晶温度分别增高了约110℃和80℃.此外,斜长石斑晶的反环带及其Ba、Sr、Fe等元素的浓度梯...  相似文献   

斑岩铜矿浅部富矿岩浆房研究进展   总被引：6，自引：0，他引：6  

李万伦 《矿床地质》2011,30(1):149-155

在主流的斑岩铜矿模型中,矿床下方都有一个浅部富矿岩浆房,为矿床的最终形成提供成矿流体.国外近年来的大量研究揭示了其基本特征,即位于地表以下约5 km,其大小直接决定着最终矿床的规模,其形态为平卧状,相对封闭,生命周期较短(一般约2 Ma).岛弧或陆缘弧环境有利于浅部富矿岩浆房形成的条件是中等挤压应力状态或挤压后应力松驰...  相似文献   

新疆东准噶尔老鸦泉富碱花岗岩型锡矿床地质及成矿流体   总被引：3，自引：2，他引：1  

王莉娟  王京彬  王玉往  龙灵利  唐萍芝 《岩石学报》2011,27(5):1483-1492

老鸦泉碱性花岗岩位于新疆北部东准噶尔地区。老鸦泉碱性花岗岩体及其内卡姆斯特、干梁子锡矿床的矿石和岩石的岩矿鉴定、稀土元素以及流体包裹体的系统研究表明,老鸦泉碱性花岗岩及其内的花岗斑岩及含矿石英岩、云英岩化锡矿体、石英脉锡矿体,实际上是富碱花岗质岩浆逐渐分异演化的同源和最终产物,锡成矿流体为中-高温、低盐度。碱性岩浆晚期分异的大量气水热液富锡、富硅、富碱、富含F、Cl、SO²₄离子及离子团,其氧逸度高、酸度高、温度高,这种热液引起花岗岩体的硅化、云英岩化等自变质作用,在该作用中随温度、压力的降低及CH₄等还原性气体及CO₂气体的逃逸,改变了成矿流体的氧化-还原环境,流体向相对还原及碱性条件转化,在新的氧化还原、酸碱度界面条件下,其携带的锡的络合物不稳定而分解,锡沉淀成矿。  相似文献