港仔地裂缝——雷州半岛西部一条纵贯晚全新世砂堤地裂缝的发现

港仔地裂缝发生于新生代以来强烈活动的琼雷凹陷北部雷州半岛的西海岸,沿构造带展布,形成于凸起和凹陷交界地区。地裂缝局部纵贯沿海岸展布的晚全新世砂堤,切过中更新世火山岩及其风化土和全新世海成阶地。根据其展布区的构造、地形地貌和形成特征,并与近几十年雷州半岛大量发生的地裂缝比较,认为港仔地裂缝可能属构造蠕变地裂缝。该地裂缝揭示了被纵贯砂堤的沉积学特征和形成于巨砾海滩和高能海浪下的古环境。砂堤上部约海拔5m砂堤岩取样¹⁴C测年为1360±60aB.P.,结合雷州半岛西海岸、西南海岸其他抬升特征,推测该地裂缝是在晚全新世该地海岸抬升或抬升后形成的。     

全新世以来山东半岛东北部海面变化的河流地貌响应

对全新世以来山东半岛东北部沿岸的相对海面（基准面）变化,不同河流有截然不同的地貌响应方式。大沽夹河型河流的下游河谷中有分别与相对海面升降对应的溯源堆积期和溯源侵蚀期,但不同规模的河流仍有差异。黄水河型河流河谷未因基准面升降而发生侵蚀或堆积,河谷仅起了输沙通道的作用。此外,大沽夹河型河流的中下游河型在相对海面上升或下降时,还可能发生相应地网状化或曲流化。     

近18 a山东半岛南部海域海面温度的长期变化研究

为探讨山东半岛南部海域海面温度的长期变化,本文利用当前国际上水平分辨率较高的多卫星观测融合数据对2003—2020年间的海面温度进行了分析研究。结果表明:(1)除威海和连云港部分近岸海域外,山东半岛南部大部分海域的海面温度显著升高,升温速率最大值可达0.083℃/a。海面增温存在显著的季节变化,主要出现在春末至秋初(4—9月),且近岸海域强于外海。(2)除青岛外海外,大部分海域的暖季开始日提前,暖季持续时间延长,其中在海州湾和烟台、威海近岸及南部海域最为显著;年最高温度升高,在连云港近海和海州湾、胶州湾等海域较为显著,但其发生日并无显著提前或者延后。(3)冬半年,山东半岛南部近岸海域和部分外海海域有较强的温度锋面,并在过去18年间显著增强。(4)海面温度在冬季的年代际变化与太平洋年代际振荡(PDO)相关性较好,但在其他季节与PDO的相关性较弱。     

Early to Middle Jurassic (ca. 182–164 Ma) fractionated granitoids in the Korean Peninsula: Implication for the tectonomagmatic history of East Asia

The Jurassic granitoids (200–164 Ma) are distributed in the Korean Peninsula due to the Paleo-Pacific plate subduction. Early Jurassic (200–182 Ma) granitoids are mainly distributed in the southern Korean Peninsula. By contrast, Early to Middle Jurassic (182–164 Ma) granitoids are distributed in the central Korean Peninsula. In this study, we report detailed petrology, zircon U–Pb ages, and whole-rock geochemistry from the Seoul–Uijeongbu and Pocheon–Gimhwa pluton units in the central Korean Peninsula. The Seoul–Uijeongbu unit is dominated by biotite granite, with minor porphyritic biotite and garnet-biotite granite while the Pocheon–Gimhwa unit consists of biotite granite and porphyritic biotite granite, garnet-biotite granite, and two-mica granite. Zircon U–Pb age from those granites gives 180–167 Ma. The granitoids in the Pocheon-Gimhwa unit formed through fractional crystallization from biotite granite and porphyritic biotite granite to garnet-biotite granite, and two-mica granite based on gradually decreasing their Nb/Ta, Zr/Hf, and Eu/Eu* ratios. The strongly fractionated granitoids are garnet-biotite granite and two-mica granite. The LILE enrichment, Ta–Nb, Sr–P, and Eu–Ti troughs, and Ba depletion in most granitoids are similar to those of granitoids due to the subduction in the arc environment. Thus, these Jurassic granitoids (180–167 Ma) are mainly peraluminous granites with moderate crystal fractionation corresponding to I-type granite. Alkali feldspar granite associated with ore mineralization occurs in the Gwanaksan pluton from the southwestern Seoul–Uijeongbu unit. The alkali feldspar granite displays distinct negative Eu anomaly with high contents of Rb, Hf, Cs, and Nb compared with other granites. These characteristics imply that alkali feldspar granite experienced strong hydrothermal activity leading to feldspar ore mineralization compared to the other granites. The formation of a wide range of moderately evolved peraluminous granitoids is presumed to be related to rapid flat-subduction during 182–164 Ma, and the mineralization-related alkali feldspar granite indicates the termination of Jurassic granitoid magmatism in the central Korean Peninsula.     

胶东辽上金矿床C、O、S、Pb同位素组成及矿床成因

辽上金矿床是胶莱盆地东北缘地区近年来新发现的一处特大型金矿床,以黄铁矿、白云石为载金矿物而区别于"焦家式"、"玲珑式"金矿床.为探讨新类型金矿床成矿流体特征和成矿物质来源,对该矿床载金白云石C、0和黄铁矿S、Pb进行了同位素分析.结果显示,载金矿物白云石中δ13Cv-PDB值为-4.60％c～-3.60‰,δ18Ov....     

深部矿阶梯找矿方法：以胶东金矿集区深部找矿为例

【研究目的】胶东是中国率先开展深部找矿并取得重大突破的地区，阶梯找矿方法在深部勘查中发挥了重要作用，研究深部找矿方法，有利于推动为中国“攻深找盲”找矿战略实施。【研究方法】本文基于胶东深部金矿找矿工作，研究了深部金矿成矿模式，分析了可控源音频大地电磁测深（CSAMT）、频谱激电测量（SIP）、大地电磁测深（MT）和反射地震等方法在深部找矿中的作用和效果。【研究结果】深部矿体常赋存于控矿断裂沿倾向的倾角变缓段，构成阶梯成矿模式，这一模式是地质构造作用与成矿物理化学条件等多种因素耦合的结果。深部矿阶梯找矿方法的要点是：在地表通过高精度地球物理探测，查明控矿断裂的深部结构和倾角变化，根据阶梯成矿模式预测深部矿的位置、规模。【结论】阶梯成矿模式为深部找矿提供了核心技术前提和可以识别的探测目标，CSAMT、SIP、MT和反射地震等方法能够探测控矿断裂的深部特征，多种地球物理方法组合是阶梯找矿方法的有效技术手段。     

Palaeomagnetic,geochronological and geological constraints on the tectonic evolution of the Mejillones Peninsula,northern Chile

Palaeomagnetic and geochronological data from an Early Palaeozoic high grade metamorphic complex (Jorgina Formation) and Jurassic layered basic intrusion (Moreno Complex) are reported from the Mejillones Peninsula of northern Chile (23–23°30'S). ⁴⁰Ar–³⁹Ar dates from the Lower Palaeozoic Jorgina Formation and the Moreno Complex are between 170 and 158 Ma, coincident with a phase of emplacement of the north Chilean coastal batholith. This suggests that intrusion and magnetization of the Moreno Complex and the metamorphism and remagnetization of the Jorgina Formation were related to batholith emplacement. Extracted stable components of magnetization from all units (17 sites) define site-mean directions with a scattered distribution. The scatter in site-mean directions is interpreted as being due to minor, localized, non-uniform, block-fault related (normal or strike-slip, or both) rotation after 158 Ma. The palaeomagnetic and geochronological data indicate that no significant large-scale latitudinal translation of crustal blocks has taken place in this part of northern Chile since the Late Jurassic. In addition, they indicate that the uniform clockwise rotation after the mid-Cretaceous which affected the adjacent Cordillera de la Costa either did not extend into the Mejillones Peninsula or took the form of localized block-fault rotations. The restriction of palaeomagnetically defined styles of rotation to discrete areas within the north Chilean forearc indicates that forearc wide block-fault rotation models are not applicable to the Pacific margin of northern Chile.     

辽东半岛顶端海域上升流长期变化特征及影响因素

利用回归分析、相关性分析等分析方法,对全球气候变暖背景下辽东半岛顶端海域上升流的变化特征及影响因素进行了研究。结果表明:夏季,辽东半岛顶端邻近海域上升流以38°52′N、120°55′E为中心,呈纺锤状分布于复州湾—辽东半岛顶端—北砣矶水道沿线海域,其位置较为固定。1988—2018年,海表温度上升流指数呈显著增加的变化趋势,其变化速率为0.27°C/10a,研究海域上升流显著增强,其中1998—2018年上升流增强尤为显著。在全球气候变暖背景下,渤海及北黄海部分海域净辐射通量的增加和夏季风场的减弱是研究海域上升流增强的两个影响因素。净辐射通量的增加和夏季风场的减弱分别有利于非上升流与上升流区的温差增大和底层冷水的上涌,进而使上升流现象增强。在长时间尺度上,ENSO(ElNi?o-SouthernOscillation)不会影响研究海域上升流强度的变化趋势,但在强厄尔尼诺发展阶段(1997年和2014年),ENSO可使研究海域纬向风(西风)增强,从而减弱研究海域上升流。     

Fluid-rock interaction modeling to constrain Au enrichment: Implication for the giant Jiaodong Au mineralization,eastern North China Craton

The devolatilization model of the metasomatized lithospheric mantle without pre-enriched gold has been proposed to account for the giant gold mineralization. An excellent example is the world-class Jiaodong gold province with >5000 tonnes Au resources in the eastern North China Craton. The auriferous fluid transport and gold enrichment during wallrock alterations are two vital processes to determine the giant gold mineralization formation in this province. However, the effects of the fluid-rock interaction with alterations on the auriferous fluid transport and gold enrichment still keep poor understanding, which leads the above model to be imperfect. The giant Jiaojia goldfield in this province recorded a wallrock alteration evolution from K-feldspar alteration to pyrite-sericite-quartz alteration, and some parts of the latter can become gold orebodies when the gold grade is >1 ppm. This study conducts thermodynamic fluid-rock interaction modeling to reveal auriferous fluid transport and coupled relationship between gold enrichment and alteration mineral assemblage based on the alteration-mineralization and ore fluid characteristics of the goldfield. The modeling of fluid-rock interaction with cooling indicates the transformation of Au-Cl complexes to Au-S complexes combined with the total sulfur concentration decrease by pyrite precipitation when cooling from ∼460 °C can trigger the dispersive gold precipitation, which should hinder the gold long-range transport to lower ambient temperature. The high oxygen fugacity at >400 °C can enhance Au-Cl complexes stability, and the low pH can maintain high total sulfur concentration in the auriferous fluid, both of which facilitate the long-range gold transport to a lower-temperature environment. The auriferous fluid would acquire higher pH by the buffering of feldspars or sericite, which was beneficial for the high-efficiency precipitations of pyrite and gold. The ankerite-siderite assemblage without pyrophyllite in the pyrite-sericite-quartz alteration zone indicates that a cumulative fluid to rock mass ratio (f/r) of 3.8–4.8 should be needed for the transformation from K-feldspar alteration to pyrite-sericite-quartz alteration according to the fluid-rock interaction modeling at 300 °C and 2000 bar. In the case of auriferous fluids with ≤200 ppb Au concentration, the single fluid-rock interaction can only elevate the gold grade to ≤0.69–0.87 ppm in the pyrite-sericite-quartz alteration zone at f/r 3.8–4.8. Therefore, the fracture-induced fluid flow coupled with fluid-rock interaction is proposed to the prerequisite to elevate the gold grade to >1 ppm in the pyrite-sericite-quartz alteration zone. The metasomatized lithospheric mantle volume for the required ore fluid and Au in the Jiaodong province is estimated according to the modeling results and alteration-mineralization characteristics, which provides a link between the mantle without abnormal Au enrichment and the alteration-mineralization processes.