河北省涞源县木吉村铜(钼)多金属矿田成矿物质来源探讨

木吉村铜(钼)矿田位于太行山脉中、北段阜平幔枝构造的北东倾伏端,涞源哑铃状杂岩体连接处西侧上盘拆离带的次级断陷盆地中,主要由斑岩型铜(钼)矿、矽卡岩型铁铜矿和外围热液脉型铅锌矿构成,是河北省目前探明的唯一大型铜(钼)多金属矿田,找矿远景巨大。鉴于矿床成矿物质来源在研究矿床成因和指导找矿中的重要作用,对木吉村矿田主要矿床矿石中黄铁矿、黄铜矿、方铅矿、辉钼矿、磁铁矿、石英和石膏等单矿物进行了硫、铅、碳、氢、氧、硅、铼等同位素测定、对比和分析。结果表明:矿田中硫同位素主值域δ34S=-3.5‰~3.2‰,主平均值为0.3‰;铅同位素206 Pb/204 Pb=15.566 0~17.072 0,平均为16.547 0,207Pb/204Pb=15.031 0~15.523 0,平均为15.258 0,208 Pb/204 Pb=36.292 0~37.375 0,平均为36.721 0;碳同位素δ13 C为-2.94‰~-2.18‰,平均为-2.62‰;硅同位素δ30 SiNBS-28值域为-0.3‰~0.2‰,平均0.0‰;辉钼矿w(Re)为(23.65~266.50)×10-6,平均值为142.33×10-6;δ18 OH2O值为-10.64‰~7.70‰,极差为18.34‰,平均值为-1.47‰,较标准岩浆水值稍低,δD值为-148.4‰~-89.0‰,极差为59.4‰,平均值为-113.7‰,略低于岩浆岩δD值域。从而认为,木吉村矿田成矿物质主要来源于地球深部,成矿溶液以岩浆水为主,部分来自大气降水。     

四川梭罗沟大型金矿区新生代碱性煌斑岩脉地球化学特征及其地质意义

木里梭罗沟大型金矿是目前四川省内探明金属量最大的金矿床,但对其研究程度较低,尤其是矿区东部大量出露的数条煌斑岩脉从未做过详细的地球化学研究。对煌斑岩脉的研究可以从地球动力学角度揭示区域构造演化,有助于对矿床成因的认识。本文选取10个煌斑岩样品,采用X荧光光谱和等离子体质谱,以及黑云母K-Ar年代学的分析测试。结果显示,其SiO2含量为42.7%~46.9%,K2O/Na2O值为1.16,黑云母K-Ar年龄为26.7~26.4Ma,说明其为形成于古近纪晚期渐新世的碱性煌斑岩。其ΣREE较高(平均708×10-6),LREE/HREE值为14.6~16.5,具弱的负Eu、Ce异常。其大离子亲石元素和轻稀土元素相对富集;高场强元素和重稀土元素亏损,且Ta、Nb和Ti具有"TNT"负异常。从而推断梭罗沟煌斑岩形成于晚碰撞与后碰撞转换时期的板内构造环境,可能起源于残留洋壳板片对地幔楔的交代富集作用,其母岩浆为石榴子石二辉橄榄岩地幔源区低程度部分熔融的产物。     

http://www.sciencedirect.com/science/article/pii/S1674987114000899

The Rajahmundry Trap Basalts（RTB） are erupted through fault-controlled fissures in the Krishna-Godavari Basin（K-G Basin） of Godavari Triple Junction,occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India.Detailed geochemical studies have revealed that RTB are mid-Ti（1.74-1.92） to high-Ti（2.04-2.81） basalts with a distinct quartz tholeiitic parentage.MgO（6.2-13.12 wt.%）,Mg^#（29-50） and Zr（109-202 ppm） suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures.Moderate to high fractionation of HREE,as indicated by（Gd/Yb）N ratios（1.71-2.31） of RTB,suggest their generation through 3-5%melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60-100 km.Low K₂O/P₂O₅（0.26-1.26）,high TiO₂/P₂O₅（6.74-16.79）,La/Nb（0.89-1.45）,Nb/Th > 8（8.35-13）,negative anomalies at Rb reflect minimum contamination by granitic continental crust.（Nb/La）_PM ratios（0.66-1.1） of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle.Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character.Geochemical compositions such as Al₂O₃/TiO₂（3.88-6.83）,medium to high TiO₂（1.74-2.81 wt.%）.positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM 1signature.Ba/Th（46-247）,Ba/La（3.96-28.51） and Th/Nb（0.08-0.13） ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle.Zr/Hf（37-41） and Zr/Ba（0.51-3.24） indicate involvement of an asthenospheric mantle source.The Rajahmundry basalts show affinity towards FOZO（focal zone mantle） and PSCL（post-Archaean subcontinental lithosphere） which reflect mixing between asthenospheric and lithospheric mantle components in their source.Origin of RTB magma is attributed to plume-lithosphere interaction and the upward movement of melt is facilitated by intrabasinal deep-seated faults in the K-G Basin.     

中国东北地区地壳、上地幔速度结构及其对矿产能源形成的控制作用

中国东北地区处于古亚洲洋和滨太平洋构造域叠合部位,地质构造极其复杂.利用东北及华北地区部分台网所接收的近震及远震走时资料获得东北地区地壳与上地幔三维P波速度结构,成像分辨率在80 km左右.成像结果表明东北地区地壳与上地幔具有较强的横向不均匀性.P波速度异常走向大体呈北东向,与该区地表构造走向一致.5 km深度的速度异...     

横向黏度变化的全地幔对流应力场初步研究

将地幔地震波速度异常转换为地幔横向黏度变化(达到3个数量级),在球坐标系下计算了瑞雷数为106、上边界为刚性、下边界为应力自由等温边界条件下的岩石层底部的地幔对流极型和环型应力场.结果表明,地幔对流极型应力场与地表大尺度构造具有良好的对应关系:俯冲带和碰撞带的应力呈现挤压状态,而洋中脊处的应力则呈现拉张状态.地幔对流环...     

Crust and upper mantle structure beneath Bohai Sea inferred from receiver function study

We analyzed teleseismic waveforms recorded by 36 stations near Bohai Sea region and obtained 2 248 high quality receiver functions.The crustal thickness (H) and average crustal vP/vS ratio (κ) as well as the Poisson's ratios beneath 34 stations were estimated using the H-κ stacking method.The results indicate that crustal thicknesses near the Liaoning province range from 30.0 to 35.5 km,and the corresponding vP/vS ratios vary from 1.72 to 1.89 which corresponds to Poisson's ratio with a range from 0.243 to ...     

利用远震接收函数的共转换点叠加方法研究华北克拉通上地幔过渡带结构

上地幔过渡带的结构形态对于研究上覆岩石圈的构造环境有十分重要的意义。本文通过对横跨华北克拉通中东部的一条北西向的测线L上分布的35个宽频带台站记录的远震数据进行接收函数的计算和共转换点叠加成像,得到了测线下方上地幔过渡带的结构。成像结果表明：华北克拉通的三个陆块处于不同的构造环境,西部陆块较为稳定,中部造山带位于地幔对...     

Slab partial melts from the metasomatizing agent to adakite,Tafresh Eocene volcanic rocks,Iran

Geochemical and mineralogical characteristics of the Eocene volcanic succession in Tafresh area of the Urumieh–Dokhtar Magmatic Assemblage (UDMA) are unique in the 2000‐km‐length assemblage. Demonstrating rather steep rare earth element (REE) patterns and the widespread presence of amphibole (+biotite) phenocrysts are two distinct characters that dominate the Eocene volcanic succession of mainly andesitic composition. Coincidence of the geochemical and mineralogical characteristics of the whole volcanic succession with adakites, rather amphibole‐ (+biotite) rich dacitic (with 61–64 wt% SiO₂) stocks and dykes, is considered as the key in unraveling the role of ‘slab‐derived melt contribution’ in petrogenesis of the volcanic succession. Slab‐derived melting has been an ongoing process that metasomatized some parts of the mantle wedge from which hybrid rocks (andesites) are derived. Basalts with distinct signatures of slab melt metasomatism are yet another support for the occurrence of slab melting. Interlayering of normal, island‐arc‐type calc‐alkaline volcanic rocks with the slab‐melt metasomatized basalts and hybrid andesites suggests that the slab melting has been motivated by the subduction. Formation of the Tafresh Caldera, the likely consequence of an explosive eruption, is compatible with the volatile‐bearing nature of the adakitic volcanism in the study area. It is indicated by the ubiquitous presence of the hydrous minerals. Beneath the Tafresh area, in Eocene time, the subducting slab seems to have reached a critical high depth that is enough for the development of amphibolite–eclogite. The slab deformation, motivated by the geometry of subduction and/or the underlying mantle's steeper geotherms, is suggested to have resulted in the slab melting that helped develop a rock assemblage unique to the UDMA.     

吉林南部辉南-靖宇地区岩石圈地幔氧化-还原状态及研究意义

吉林省南部辉南-靖宇地区第四纪碱性玄武岩中的地幔包体主要为尖晶石相二辉橄榄岩和方辉橄榄岩。二辉橄榄岩和方辉橄榄岩的平衡温度分别为770~1000℃和850~1025℃,对应的氧逸度 (f_O2)值分别为FMQ -0.70至+0.34 (均值为FMQ -0.06) 和FMQ -0.46至+0.05 (均值为FMQ -0.15),它们与深海橄榄岩(abyssal peridotites)以及软流圈地幔的f_O2相似。橄榄岩的f_O2值,连同其全岩化学成分(如Mg^#、Al₂O₃、CaO、Ni、Co和Cr)和矿物化学成分(如橄榄石的Fo、尖晶石的Cr^#和Mg^#,以及辉石的Mg^#)特征,表明辉南-靖宇地区龙岗火山群下面的岩石圈地幔很可能是在晚中生代以来,伴随着华北克拉通和扬子板块的碰撞以及来自东侧太平洋板块和北侧蒙古-额霍次克(Mongolo-Okhotsk)板块分别向西和向南的俯冲叠加,原来的古老岩石圈失衡、塌陷(拆沉？),取而代之的深部软流圈底辟、上涌,又经历了低度部分熔融的产物。