卡尔斯伯格脊 60°~61°E洋脊段多波束后向散射特征及其对构造与岩浆作用强度的指示          下载免费PDF全文

杨驰  韩喜球  王叶剑  李洪林  邱中炎  吴招才 《海洋学研究》2018,36(3):37-49

多波束声纳数据可以有效记录海底地形地貌和底质特征信息。本文利用船载多波束数据对慢速扩张的卡尔斯伯格脊60°~61°E洋脊段的典型构造地貌单元的后向散射强度特征进行了研究,在此基础上,分析了该洋脊段的构造和岩浆作用强度特征。结果表明,洋脊段I以构造拉张作用占主导,脊轴及附近后向散射强度为-29 dB左右,裂谷壁高差可达1 200 m以上,裂谷内断裂发育,裂谷侧翼高度与裂谷宽度的比值为78.7~126.2,裂谷两侧翼部线性构造较少,但轴向正断层面更宽,倾角更小;与洋脊段裂谷中段相比,末端火山活动频率较低但喷发规模较大,火山机构数量和体积也更大,且可发育深大断裂获取深部热源。洋脊段II以岩浆作用占主导,脊轴及附近后向散射强度达-35 dB,裂谷内轴向火山脊发育,裂谷壁高差小于500 m,裂谷侧翼高度与裂谷宽度的比值为77.6~116.8,裂谷两侧翼部线性构造数量众多、长宽比较大且呈近似对称,相邻线性构造之间沉积物广泛分布。通过提取挖掘与底质属性密切相关的多波束后向散射强度数据,结合海底地形地貌的分析,可以为洋中脊的构造和岩浆作用强度的定量研究提供有效的证据。  相似文献   

吉中- 延边地区燕山期岩浆作用与矿床成矿系列研究     

赵华伟  李德洪  臧兴运  彭玉鲸  马晶 《地质学报》2020,94(1):241-254

运用矿床的成矿系列理论,以构造岩浆演化为基础,对吉中- 延边成矿带与燕山期岩浆作用有关的矿床成矿规律进行了分析总结。研究表明,受古太平洋板块俯冲方向、速度的制约,吉中—延边地区燕山期构造岩浆活动复杂,总体上可分为5次成岩成矿事件：① 晚三叠世初基性超基性岩侵入,形成红旗岭铜镍矿床等岩浆型矿床;② 晚三叠世—早侏罗世初,吉中地区高钾钙碱性岩浆活动,形成兰家金矿床等岩浆热液型矿床,延边地区中低钾钙碱性—高钾钙碱性岩浆活动,形成前山金矿床等火山- 潜火山岩型矿床;③ 早侏罗世末—中侏罗世初,富铝酸性岩浆活动,形成大黑山钼矿床等斑岩型钼矿床;④ 中侏罗世末—晚侏罗世初,研究区以抬升剥蚀为主,成岩成矿作用较弱;⑤ 晚侏罗世末—早白垩世,吉中地区高钾钙碱性岩浆活动,形成二道甸子金矿床等岩浆热液型矿床,延边地区中低钾钙碱性—高钾钙碱性岩浆活动,形成小西南岔金铜矿床等火山- 斑岩型矿床。在建立吉中—延边地区与燕山期岩浆作用有关的矿床成矿系列的基础上,进一步划分为6个矿床成矿亚系列,各亚系列在时间、空间上既有联系,又有区别,显示了成矿作用的复杂性。  相似文献   

秦岭造山带中酸性岩浆作用中Zr、Hf地球化学行为探究     

米宝昕  刘宏  耿昭  王洪刚  王晓晨 《四川地质学报》2020,40(1):143-146

秦岭造山带属于中央造山带的重要组成部分,由不同时期,不同类型造山作用所形成的各种构造带复合组成,具复杂时空组合关系,成为一个特色鲜明的大陆造山带,故对其研究一直热度不减。本文从秦岭造山带中各种中酸性岩的Zr、Hf地球化学行为入手,通过对比不同时代、不同岩性中Zr、Hf的含量及Zr/Hf比值,分析Zr、Hf,在不同时代、不同SiO2含量的岩浆中的特性及演化规律,以此探讨秦岭造山带中岩浆在不同时代和不同构造背景下的演化规律。  相似文献   

冲绳海槽构造演化及其与岩浆、热液和沉积作用的关系：研究进展与展望     

刘伟  孙钰杰  郑涵月  辛孟燃  何炜  魏桐  郭诗岳  陈思放  刘雯文  冯雨歌 《高校地质学报》2020,26(6):680-690

冲绳海槽是西太平洋沟-弧-盆体系中典型的弧后盆地。其独特的大地构造位置,岩浆、热液活动与沉积记录一直是学术界研究的热点。基于前人的研究成果,本文综述了冲绳海槽的构造活动对岩浆、热液与沉积的控制作用。菲律宾海板块的俯冲导致了冲绳海槽的形成,并发生了弧岩浆、弧后岩浆和斜切弧后岩浆作用,这三种岩浆作用导致了热液活动在平面分布上的三种不同分区。岩浆的发育和菲律宾海板块俯冲造成的断裂系统为冲绳海槽热液的发育分别提供了热源和通道。在~416 ka发生的浙闽隆起带沉降,导致了冲绳海槽北部的沉积物由粗变细。最后针对冲绳海槽的研究现状,文章对未来的进一步研究作了展望。  相似文献   

扬子板块西缘新元古代典型中酸性岩浆事件及其深部动力学机制:研究进展与展望     

赖绍聪  朱毓 《地质力学学报》2020,26(5):759-790

华南板块发育有巨量新元古代岩浆岩,因而是研究罗迪尼亚（Rodinia）超大陆演化期间华南板块地幔属性、地壳演化和壳幔相互作用最理想的场所。虽然在扬子西缘新元古代镁铁质和酸性岩浆作用方面已有大量的研究,但是在系统研究中酸性花岗岩类所代表的不同深部动力学意义的方面还较为薄弱。文章基于团队近期对于扬子板块西缘新元古代典型花岗岩类的研究成果,系统揭示不同深度层次的岩浆作用。最新研究支持扬子西缘新元古代受控于俯冲构造背景,除发生俯冲流体和板片熔体交代地幔作用外,最新识别的ca.850~835 Ma高Mg#闪长岩指示俯冲沉积物熔体也参与了地幔交代作用。Ca.840~835 Ma过铝质花岗岩的发现说明扬子西缘新元古代时期不仅存在新生镁铁质下地壳的熔融,也发生了俯冲背景下成熟大陆地壳物质的重熔。Ca.780 Ma Ⅰ型花岗闪长岩-花岗岩组合揭示了俯冲阶段后期板片回撤断离后软流圈地幔瞬时上涌引发的不同地壳层次的岩浆响应。从ca.800 Ma的增厚下地壳来源的埃达克质花岗岩到ca.750 Ma的酸性地壳来源的A型花岗岩的出现,表明扬子西缘新元古代时期经历了俯冲有关的地壳增厚到俯冲后期弧后扩张背景下的区域性地壳减薄。   相似文献   

东海中段钓鱼岛隆起的内部结构与演化          下载免费PDF全文

李珂迪  李春峰  姚泽伟  陶天生 《海洋学研究》2020,38(4):1-15

由于钓鱼岛隆起的地质与地球物理资料相对缺乏,前人对该区域系统研究较少,关于其构造演化存在许多争议。本文通过重磁资料,结合反射地震剖面解释研究了西湖凹陷东侧的中段钓鱼岛隆起的构造与沉积特征,并进一步完善了其演化模式。研究结果表明,隆起内部存在多个残余凹陷,残留地层具有“北多南少”的分布特征,据此以舟山-国头断裂为界,可以将中段钓鱼岛隆起进一步分为南、北两个亚段。南、北亚段边界处在舟山-国头断裂的延长线上。同时,隆起西部的岩浆岩体分布于平坦剥蚀面T20之下,而东部存在岩浆活动引起的“基底尖峰”,空间重力异常的梯度带恰好与“基底尖峰”的西缘对应,以“基底尖峰”的西缘为界,将中段钓鱼岛隆起大致分成东、西两区,其中西区又可以进一步分为发育岩浆岩体的西Ⅰ区和局部残留凹陷的西Ⅱ区。西区由西湖凹陷经构造反转与岩浆活动改造而成,东区保留了古隆起。综合分析推断,中段钓鱼岛隆起是在古隆起的基础上经历多次构造与岩浆活动演化而成。  相似文献   

科科斯脊玄武岩斜长石矿物化学及地质意义     

葛振敏  鄢全树  赵仁杰  施美娟 《海洋学报》2020,42(7):93-107

综合大洋钻探计划(IODP) 334和344航次在U1381站位处的两个钻孔(A孔和C孔)获得了中美洲西海岸外科科斯脊基底拉斑玄武岩,对其岩浆过程开展研究可为理解其岩石成因提供重要依据。本文对科科斯脊玄武岩中斜长石斑晶和微晶进行了详细的原位主微量元素分析,结果表明,斜长石种属为培长石、拉长石及少量中长石。部分斜长石斑晶具有正环带结构;但多数斜长石斑晶不具有明显环带,仅从核部到边部存在微弱的成分变化。斜长石斑晶与微晶的微量元素差别较大:斜长石斑晶富集轻稀土和大离子亲石元素、亏损高场强元素,且具有明显的Eu正异常;斜长石微晶不相容元素含量通常高于斜长石斑晶。根据斜长石温度计计算获得斜长石斑晶结晶温度为1 050～1 253℃,斜长石微晶结晶温度为866～1 033℃。基于以上特征,推测斜长石斑晶核部是相对原始岩浆的产物,而斑晶边部以及微晶是演化岩浆的结晶产物。斜长石斑晶的成分变化及熔蚀麻点结构是由于岩浆补给及岩浆减压上升造成的。最后,本研究推测科科斯脊基底玄武岩来自于开放的岩浆房,且岩浆房内可能存在原始岩浆的不断注入及岩浆对流。  相似文献   

Interplay between geochemistry and magma dynamics during magma interaction: An example from the Sithonia Plutonic Complex (NE Greece)     

G. Christofides  D. Perugini  A. Koroneos  T. Soldatos  G. Poli  G. Eleftheriadis  A. Del Moro  A.M. Neiva 《Lithos》2007,95(3-4):243-266

Orogenic granitoids often display mineralogical and geochemical features suggesting that open-system magmatic processes played a key role in their evolution. This is testified by the presence of enclaves of more mafic magmas dispersed into the granitoid mass, the occurrence of strong disequilibrium textures in mineralogical phases, and/or extreme geochemical and isotopic variability.

In this contribution, intrusive rocks constituting the Sithonia Plutonic Complex (Northern Greece) are studied on the basis of mineral chemistry, whole-rock major, trace element geochemistry, and Sr and Nd isotopic composition. Sithonia rocks can be divided into a basic group bearing macroscopic (mafic enclaves), microscopic (disequilibrium textures), geochemical, and isotopic evidence of magma interaction, and an acid group in which most geochemical and isotopic features are consistent with a magma mixing process, but macroscopic and microscopic features are lacking.

A two-step Mixing plus Fractional Crystallization (MFC) process is considered responsible for the evolution of the basic group. The first step explains the chemical variation in the mafic enclave group: a basic magma, represented by the least evolved enclaves, interacted with an acid magma, represented by the most evolved granitoid rocks, to give the most evolved enclaves. The second step explains the geochemical variations of the remaining rocks of the basic group: most evolved enclaves interacted with the same acid magma to give the spectrum of rock compositions with intermediate geochemical signatures. A convection–diffusion process is envisaged to explain the geochemical and isotopic variability and the lack of macroscopic and petrographic evidence of magma interaction in the acid group.

The mafic magma is presumably the result of melting of a mantle, repeatedly metasomatized and enriched in LILE due to subduction events, whereas the acid magma is considered the product of partial melting of lower crustal rocks of intermediate to basaltic composition.

It is shown that Sithonia Plutonic Complex offers the opportunity to investigate in detail the complex interplay between geochemistry and magma dynamics during magma interaction processes between mantle and crustal derived magmas.  相似文献   

Volatile (S,Cl and F) and fluid mobile trace element compositions in melt inclusions: implications for variable fluid sources across the Kamchatka arc   总被引：2，自引：0，他引：2  

Tatiana Churikova  Gerhard Wörner  Nikita Mironov  Andreas Kronz 《Contributions to Mineralogy and Petrology》2007,154(2):217-239

Volatile element, major and trace element compositions were measured in glass inclusions in olivine from samples across the Kamchatka arc. Glasses were analyzed in reheated melt inclusions by electron microprobe for major elements, S and Cl, trace elements and F were determined by SIMS. Volatile element–trace element ratios correlated with fluid-mobile elements (B, Li) suggesting successive changes and three distinct fluid compositions with increasing slab depth. The Eastern Volcanic arc Front (EVF) was dominated by fluid highly enriched in B, Cl and chalcophile elements and also LILE (U, Th, Ba, Pb), F, S and LREE (La, Ce). This arc-front fluid contributed less to magmas from the central volcanic zone and was not involved in back arc magmatism. The Central Kamchatka Depression (CKD) was dominated by a second fluid enriched in S and U, showing the highest S/K₂O and U/Th ratios. Additionally this fluid was unusually enriched in ⁸⁷Sr and ¹⁸O. In the back arc Sredinny Ridge (SR) a third fluid was observed, highly enriched in F, Li, and Be as well as LILE and LREE. We argue from the decoupling of B and Li that dehydration of different water-rich minerals at different depths explains the presence of different fluids across the Kamchatka arc. In the arc front, fluids were derived from amphibole and serpentine dehydration and probably were water-rich, low in silica and high in B, LILE, sulfur and chlorine. Large amounts of water produced high degrees of melting below the EVF and CKD. Fluids below the CKD were released at a depth between 100 and 200 km due to dehydration of lawsonite and phengite and probably were poorer in water and richer in silica. Fluids released at high pressure conditions below the back arc (SR) probably were much denser and dissolved significant amounts of silicate minerals, and potentially carried high amounts of LILE and HFSE. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Age constraints on the evolution of the Austroalpine basement to the south of the Tauern Window   总被引：1，自引：0，他引：1  

Siegfried Siegesmund  Till Heinrichs  Rolf L. Romer  Daniel Doman 《International Journal of Earth Sciences》2007,96(3):415-432

The Austroalpine basement to the south of the Tauern Window once was part of the northern margin of Gondwana. It includes the “Altkristallin” and the phyllitic Thurntaler Complex. In the Altkristallin (AMU, MPU), suites of arc-related metamafic sequences occur together with calc-alkaline metagranite. SHRIMP U–Pb dating of zircon from calc-alkaline metagranite associated with an eclogitic amphibolite give an age of 470 ± 3 Ma interpreted as the age of protolith emplacement. In the Thurntaler Complex, metaporphyroids occur together with tholeiitic as well as alkaline within-plate basalt-type metabasite. The metaryholites of this association give a crystallization SHRIMP age of 477 ± 4 Ma, which suggests contemporaneity of arc-related and extensional settings in the Austroalpine basement units. The age data demonstrate widespread magmatic activity associated with the Early-Ordovician amalgamation at the end of the 550–470 Ma subduction–accretion–collision cycle. The Pb–Pb and U–Pb systematics of step-wise leached staurolite and kyanite from the peak-metamorphic assemblage of the Altkristallin indicate that (1) step-wise leaching of staurolite and kyanite yields the age of inclusions rather than the host; (2) zircon inclusions in staurolite suggest an Ordovician or older age for the precursor of the staurolite-schists; (3) the weighted average of the ²⁰⁶Pb/²³⁸U data of the various leaching steps yields a Variscan age for the inclusions (ilmenite, biotite, and andesine). Since these inclusions are part of the metamorphic mineral assemblage, this age provides a minimum estimate for staurolite growth, i.e., metamorphism. Thus, the Pb–Pb and U–Pb systematics of staurolite provide evidence for a Variscan metamorphism of the Austroalpine basement, e.g., MPU, AMU and Thurntaler Complex, to the south of the Tauern Window.  相似文献