闽南沿海地区变质变形侵入岩时序划分及其地质意义

根据接触关系,结合同位素测年资料、岩石变形变质特征及原岩的岩石学、矿物学等特征,将闽南沿海地区变质变形侵入岩划分为早侏罗世东山序列(石英闪长岩—花岗闪长岩—二长花岗岩—正长花岗岩)、晚侏罗世古美山序列(花岗闪长岩—二长花岗岩—正长花岗岩)(145.4 Ma,LA-ICPMS锆石U-Pb)及早白垩世早期漳浦序列(石英闪长岩—花岗闪长岩—二长花岗岩—正长花岗岩)(121.5～139.4 Ma,锆石U-Pb)。并据侵入岩产状、岩石学、矿物学、岩石化学及地球化学等特征,分析各序列花岗岩的成因及形成时的构造环境,认为早侏罗世东山序列岩浆来源为壳-幔混合源(I型),形成于构造体制由挤压转向拉张转换期大陆上隆(碰撞后隆升)的构造环境(PAG);晚侏罗世古美山序列岩浆来源为幔-壳混合源(I-S型),属与板块碰撞(俯冲作用)有关的同碰撞花岗岩(ACG);早白垩世早期漳浦序列岩浆来源为壳-幔混合源(I-S型),属构造体制由挤压向拉张转化时期幔-壳源型花岗岩(KCG)。该区变质变形花岗岩序次的厘定及其成因、形成环境的研究为长乐—南澳断裂带中生代构造演化提供了依据,并为东南沿海地区寻找与中生代岩浆作用有关的钨、锡、铜、钼等矿产提供找矿理论依据。     

鲁西地区中生代侵入岩期次划分

鲁西地区中生代有2个岩浆活动时期,中侏罗世岩浆活动规模较小,形成铜石杂岩体,锆石SHRIMP U Pb年龄167.9-183Ma,加权平均值为（175.7±3.8）Ma;早白垩世岩浆活动范围较广,生成多种岩石系列,形成济南—埠村—邹平—淄博金岭一带杂岩体和沂南县铜井、莱芜、蒙阴虎头崖、临朐铁寨等杂岩体,锆石SHRIMP和LA ICP MS U Pb测年结果为128-134Ma。     

Geology and Origin of the Dongping Alkalic-Type Gold Deposit, Northern Hebei Province, People's Republic of China

Abstract: The Dongping deposit, located near the center of the northern margin of the north China craton, is one of the largest gold deposits in China. It is spatially, temporally, and genetically associated with the shallowly-emplaced Hercynian Shuiquan-gou alkaline intrusive complex. The complex intrudes high-grade metamorphic rocks of the Archean Sanggan Group along a deep-seated fault zone within the north China craton. Four major ore bodies (Nos. 1, 2, 22, and 70), consisting mainly of a set of en echelon lenses and veins, have been delineated at the Dongping deposit. Hypogene hydrothermal activities can be divided into four periods from early to late including: (1) gold-bearing K–feldspar–quartz stockworks and veins; (2) disseminated sulfide and gold zones; (3) gold-bearing quartz veins, and (4) barren calcite-quartz veins. Individual veins and stockwork systems can be traced along strike for 125 to 600 m and downdip for 100 to 600 m; they range from 0. 5 to 3 m in thickness. The mineralogical composition of the ore in the first three hypogene periods is relatively simple. It is composed of pyrite, galena, sphalerite, magnetite, specularite, chalcopyrite, native gold, electrum, calaverite, and altaite. Gangue minerals include K–feldspar, quartz, sericite, chlorite, epidote, albite, and calcite. Ore grade averages 6 g/t Au, but varies between 4. 14 and 22. 66 g/t Au. Gold is generally fine-grained and not visible in hand specimen. Fluid inclusions in ore-bearing quartz of periods 1, 2, and 3 are CO₂–rich, variable salinity (2. 5–21 wt% equiv. NaCl), and have variable homogenization temperatures of 195° to 340°C. Quartz in the gold-bearing K–feldspar–quartz stockworks (period 1), disseminated sulfide and gold zones (period 2), and the gold-bearing quartz veins (period 3) has calculated δ¹⁸O_H2O values between –1. 7 and 6. 9%, and δ values of fluid inclusion waters between –101 and –66%. All these isotope data of the ore-forming fluids plot between the magmatic fluid field and the meteoric water line. Sulfide minerals disseminated in host rocks show positive δ³⁴S values of 1. 9 to 3. 5%. Pyrite separates from he gold-bearing K–feldspar–quartz stockworks and veins (period 1) have a δ³⁴S range of –4. 3 to 0. 5%, whereas δ³⁴S values of pyrite, chalcopyrite, galena, and sphalerite from the disseminated sul-fide and gold zones (period 2) and the gold-bearing quartz veins (period 3) vary from –5. 3 to –13. 4%. Gold ores are also characterized by relatively radiogenic lead isotope compositions compared to those of the alkaline syenite host rock. The data are interpreted as indicative of a mixing of lead from the alkaline intrusive complex with lead from Archean metamorphic rocks. The combined fluid inclusion measurements, sulfur, oxygen, hydrogen, and lead isotope data, and petrological observations indicate that the Dongping deposit was formed from the mixing of these magmatic fluids with meteoric waters. The deposit is, therefore, believed to be a product of Hercynian alkaline igneous processes within the north China craton.     

新疆普鲁一带米兰岩群组成及地质构造意义

通过在新疆西昆仑开展的1∶25万《于田》、《伯力克》幅区调项目,从库地—其曼特缝合带北侧,前人划分的长城系中划分出来一套中深变质的片麻岩系,并从中解体出一套变质中酸性侵入体—TTG岩系,其余岩石组合经区域地层对比,厘定为米兰岩群。并对其岩石组合、岩石化学、原岩恢复及形成环境等方面进行了研究。进一步为研究"古昆仑洋"的演化及塔里木板块南缘基底的组成及演化特征提供了新的资料。     

新疆喀拉通克镁铁质岩体群的岩石成因研究

喀拉通克镁铁质岩体群位于准噶尔板块北缘,由13个小岩体组成。主要岩石类型为方辉橄榄岩、橄榄苏长岩、辉长苏长岩、辉长岩、淡色辉长岩、辉长闪长岩等。主要造岩矿物为贵橄榄石、普通辉石、紫苏辉石、斜长石和数量较多的褐色普通角闪石、黑云母等。主量元素分属钙碱性系列、岛弧拉斑玄武岩系列和具有MORB属性的拉斑玄武岩系列。大多数样品具有高LREE/HREE比值、富集大离子亲石元素,相对亏损高场强元素（Nb、Ta、Ti）。ε_Nd(t)=＋6.2~＋8.2,4件样品的ε_Sr(t)=-0.6~-36.3,另有1件样品为+36.5;(²⁰⁶Pb/²⁰⁴Pb) _i=17.784~18.008,(²⁰⁷Pb/²⁰⁴Pb) _i=15.400~15.555,(²⁰⁸Pb/²⁰⁴Pb) _i=36.973~37.560。元素地球化学和Nd、Sr、Pb、Os、O、S同位素体系证明,岩浆仅在局部遭受了同化混染作用。原生岩浆为高镁的拉斑玄武岩浆（MgO=11.6%）。岩浆在上侵和运移过程中经历了以单斜辉石为主的暗色矿物的广泛分离结晶作用和斜长石的凝聚,导致了淡色辉长岩的广泛分布和超镁铁岩的严重缺失。岩浆源区由被消减板片交代的地幔楔物质和软流圈地幔物质组成,因而富集不相容元素和水,并因交代作用与岩浆生成的时差短,而保持放射成因同位素的亏损状态。在岩石圈根部拆沉和软流圈地幔上涌过程中生成了喀拉通克镁铁质岩体群。     

内蒙古武川西北部早二叠世岩浆活动及其构造意义

内蒙古武川县西北元恒永一带,出露一套早二叠世辉长苏长岩、石英闪长岩、二长花岗岩组成的钙碱性岩系。该套岩石以稀土总量中等、轻稀土富集、无明显的Eu异常等特征显示幔源成因,尽管有不同程度的地壳物质混入,地球化学特征指示岩体形成于板块碰撞前的岛弧环境。岩体中发育弱的片麻理构造,石英闪长岩和二长花岗岩中有较多暗色细粒黑云闪长岩包体,包体的扁平面平行片麻理;包体的应变测量显示侵位过程中岩浆与包体粘度差不大,包体发生了旋转变形,岩浆侵位受区域构造应力控制。石英闪长岩中单颗粒锆石U-Pb年龄为(282.3±4.6)Ma,表明其形成时代为早二叠世。岩体的形成可能与古亚洲洋向华北板块俯冲有关,显示出华北板块北缘的安第斯型大陆岛弧背景。     

河北矾山钾质碱性超镁铁岩-正长岩杂岩体的锆石SHRIMP U-Pb年龄

作为华北陆块北缘的碱性岩体之一,河北矾山钾质碱性超镁铁岩-正长岩杂岩体赋存着中国最大的内生磁铁矿-磷灰石矿床。关于其形成时代,已经发表的K-Ar、Rb-Sr和Sm-Nd法定年结果差别较大,因此需要采用更精确的定年方法限定岩体的形成时代。通过对矾山杂岩体的辉石正长岩样品进行SHRIMP锆石U-Pb定年,得到了218±2Ma的结果。由于定年样品取自构成矾山杂岩体主体、形成最晚的第三岩相带,这个年龄限定矾山杂岩体形成于晚三叠世。现有的锆石U-Pb年代学资料表明,晚三叠世侵入岩在华北陆块北缘、东缘、南缘普遍存在,成为中国东部晚三叠世构造-岩浆活动的显著特征之一。     

华北地块中东部中生代侵入杂岩中角闪石和黑云母的40Ar/39Ar定年:对岩石圈减薄时间的制约

华北地块中东部中生代侵入杂岩存在有富闪侵入岩和花岗闪长岩类两套岩石组合.对其中 8个侵入杂岩体中的角闪石和黑云母进行了 40Ar/39Ar定年研究.山西临汾塔儿山正长闪长斑岩、山西长治西安里岩体和河南安阳东冶岩体富闪侵入岩中角闪石的 40Ar/39Ar坪年龄分别为(124.9± 0.3)Ma,(127.7± 0.3)Ma和(127.1± 0.1)Ma;鲁西临朐铁寨正长闪长岩和枣庄流井花岗闪长斑岩中角闪石的 40Ar/39Ar坪年龄均为(124.9± 0.2)Ma;鲁西莱芜铁铜沟辉石闪长岩和蒙阴虎头崖花岗闪长斑岩中黑云母的 40Ar/39Ar坪年龄分别为(132.8± 0.3)Ma和(124.4± 0.3)Ma;皖北管店花岗闪长斑岩中角闪石的 40Ar/39Ar坪年龄为(126.9± 0.2)Ma.上述结果显示华北地块中生代的岩浆活动主要发生在早白垩世.含有丰富幔源捕虏体的富闪侵入岩类和具有地壳成因的花岗闪长岩类岩石的共存,暗示早白垩世华北地块中生代岩石圈减薄达到了峰期.     

青海祁漫塔格晚古生代—早中生代侵入岩构造背景与成矿关系

造山带成矿作用研究是当代成矿学重大研究的前沿,通过对东昆仑造山带北西段祁漫塔格晚古生代—早中生代侵入岩研究,表明祁漫塔格与东昆仑东段晚古生代—早中生代构造演化具有一定相似性。早二叠世之前为洋盆扩张期,早二叠世空谷期洋盆扩张结束,俯冲作用开始,发育钾玄岩系列POG型花岗岩,形成斑岩型铜矿。中三叠世为主俯冲阶段,发育高钾钙碱性大陆弧花岗岩(CAG),形成矽卡岩型铁多金属矿。晚三叠世卡尼—诺利期,大洋闭合,进入后碰撞陆内造山阶段,发育高钾钙碱性钾玄岩系列后造山花岗岩(POG),形成了斑岩钼矿和矽卡岩型铁多金属矿。     

陕南汉中地区新元古代岩浆岩U-Pb年代学

用单颗粒锆石U-Pb稀释法测定了扬子地块北缘汉南地区新元古代岩浆岩的年龄,获得孙家河组火山岩成岩年龄为840～ 820Ma,汉南侵入杂岩中五堵门复式花岗岩体中英云闪长岩的结晶年龄为764Ma±2Ma,黄家营复式岩体中钾长花岗岩的结晶年龄为778Ma±5Ma,表明扬子地块北缘汉南地区岩浆岩分别形成于新元古代晋宁期和澄江期.结合这些岩浆岩的地质和地球化学特点,认为其成因可能与华南新元古代裂解事件有关.