【作者】 毛景文；

【导师】 宋叔和； 陈毓川；

【作者基本信息】 中国地质科学院 ， 矿床学， 1988， 博士

【摘要】 桂北九万大山—元宝山锡多金属成矿区位于扬子古陆南部边缘活动带，区内火成岩种类繁多和成岩成矿条件十分特殊。诸多地质学家认为华南地区地质演化特点是从扬子古陆边缘向外逐渐增殖，若对古陆边缘地区进行较好的研究必将得到认识华南地质史及成岩成矿的钥匙。近些年来，不少学者纷至踏来，对有关岩石和矿床进行了大量的研究，并获得了一些珍贵的资料和有意义的成果。在前人工作的基础上，笔者经过近四年的野外和室内工作，通过区域地质、地层地球化学、岩石学、岩石化学、微量元素、同位素和流体包裹体等方面综合研究了区内火成岩系列和锡多金属矿床成矿系列的成因演化特点和成岩成矿规律，取得如下一些新的认识：1、桂北九万大山—元宝山地区是一个富成矿元素Sn、W、Cu、Pb．Zn、Cr、Co、Ni、Sb，碱质组分K和Na，挥发组分B、F和Cl及不相容元素Rb、Sr、Li、Ba，U和Th等的地球化学异常区。该异常区内的最大特征是无论地壳还是地幔都富有上述元素，这正是锡多金属矿床成矿的基础。2、用Sm-Nd同位素年代学方法测得四堡群成岩时代为2412Ma。由此可以认为扬子地块最古老的地层形成于早元古代而不是中晚元古代。3、通过区域岩石序列、岩石学、岩石组构、地球化学、微量元素等方面研究，确认原命名的层状基性-超基性侵入岩是一套镁铁质一超镁铁质火山杂岩，其中部分为科马提岩。4、从岩石序列、矿体产状、矿石构造和硫同位素等方面证明原称之谓正岩浆熔离Cu-Ni硫化物矿床是一种与辉石质科马提岩有关的火山岩型铜镍矿床，系我国一个新的矿床类型。5、黑云母花岗岩是锡多金属矿床成矿之主因。它来源于地壳，并分两个阶段于雪峰期定位。黑云母花岗岩对成矿的贡献有两个突出的方面：其一是其在重熔生成演化过程中，经高度分异作用，将原各地质体中的锡多金属元素分馏寓集，为成矿奠定了一个良好的基础。其二，花岗岩在定位期间，其本身的热能导致周围地层中的地下水形成了一系列热卤水循环系统，生成了许多的贱金属硫化物矿床。6．收集了我国的有关资料，从岩石学、矿物学、地球化学、微量元素、过渡族元素、不相容元素和同位素等方面建立了我国含锡花岗岩的系列判别准则。并尝试对研究区内的花岗质岩石进行判别，得到了良好的效果。7．长时间以来，本洞等花岗闪长岩体被认为是华南地区典型的幔源分异型花岗岩，近年又有人提出其为I型花岗岩，并与三防、元宝山、平英等S型花岗构成了大陆边缘成对花岗岩类。此次工作，通过进一步对该套岩体的岩石学、矿物学、地球化学、数量元素、稀土元素和同位素等方面研究，并考虑了区域地质演化和地质时代等因素，基本上证明其并非幔源分异型花岗岩，也不是典型I或S型花岗岩，而是一种以地壳物质为主、地幔物质为辅的混源重熔型花岗岩，该岩石的Sm-Nd同位素模式年龄恰与四堡群的Sm-Nd同位素等时线年龄一致，说明前者源于后者，花岗闪长岩之所以没有成矿，关键在于本身的分异程度太低，它们较小的体积，也不足以引起地下热卤水矿床的产生。8、发现了四堡期昙状，透镜状体具层纹构造的电英岩锡矿化体。此举不仅将我国锡矿成矿时代从800Ma左右推前至2412Ma左右，而且证明了该区锡矿化的多旋回性和继承性，也提出了一个与镁铁质岩浆活动有关的热卤水锡矿化的实例。9．本文从成矿系列角度研究了与雪峰期黑云母花岗岩有关的锡多金属矿床。该成矿系列的矿床在空间上有序分带，即以岩体为中心的顺向分带为：云英岩型锡矿床→电英岩型锡矿床→锡石石英型锡矿床→锡石硫化物型锡矿床→铜铅锌金属硫化物矿床→铅锌硫化物矿床→锑矿床，逆向分带为：锡多金属矿床→铜铅锌硫化物矿床→铅锌硫化物矿床。造成这种分带现象的内在因素是高热能且富含矿热液的黑云母花岗岩的高侵定位和岩体热中心的向下移动。该成矿系列时间递变可分为三个成矿期(锡石硅酸盐成矿期、锡石硫化物成矿期和贱金属硫化物成矿期)和六个成矿阶段。10、关于内陆的成矿作用，岩浆热液成矿论者将花岗岩视为成矿物质唯一来源，而层控成矿论者将花岗岩仅看作成矿的能源，本区的工作初步证实，部分矿质(Sn。W、Cu等元素)与花岗岩有关，另一部分矿质(Cu、Pb、Zn、Sb等)与围岩石有关。锡多金属矿床的成矿水以岩浆水为主、混合有大气降水，而贱金属硫化物矿床的成矿水主要为大气降水。由此可以认为这正是在同一成矿系列中内生成矿作用与外生成矿作用的辩证统一。11、提出了交代体系的概念．并运用了交代系列和交代建造的学术思想。以矿化蚀变期为经线，以交代系列为纬线，探讨了交代网落中各个子系列的化学变化、条件、演化方向和最终结果。12，从成因矿物、矿石和蚀变岩地球化学、同位素和包裹体地球化学、成岩成矿物理化学等方面探讨了与黑云母花岗岩有关的锡多金属矿床成矿系列的成矿环境和组成演绎。13．提出了以锡多金属地球化学异常场客观存在为基础，以构造运动为主导，以黑云母花岗岩分异演化及热功能作用为主因的成矿思路。此外，还建立了该区域成矿系列的成矿模型。14、与周科子一起发现了一个新矿物，属Cu与Ni的金属互化物，具主要成分为Cu、28.52％、Ni、64.81％和Fe，6.58％。更多还原

【Abstract】 The metallogenic region of Jiuwandashan-Yuanbaoshan tin polymetallic deposits in North Guangxi is located in the marginal active belt of Yangtze oldland where there is a great deal of various igneous rocks and a very special rock-forming and metallogenic environment. Some gelolgists have pointed out that the main characteris-tics of gelolgical evolution of South China was that the crust grew from the margin of Yangtze oldland outward. So if the oldland margin is well studied, it is possible to get a key for knowing the geological evolutional history and rock-forming and metallogenic processes in South China. Many geologists have come to the region and obtained some precious and interesting data on the petrology and ore deposits through their research works.Based on the previous studies, this work is mainly aimed at the geneses and evo-lutions of the igneous rock series and the metaliogenic series by the study on regional geology, strata geochemistry, petrology, model mineralogy, petrochemistry, trace ele-ments, isotopes and fluid inclusion, and some new scientific results are obtained as fol-low:1. The Jiuwandashan-Yuanbaoshan region is a geochemical anomalous field en-riched in metallogenic elemcnts Sn, W, Cu, Pb, Zn, Cr, Co, Ni and Sb, alkali cornpenents K and Na, volatilcs B, F and Cl, as well as incompatible clcmcnts Rb, Sr, Li, Ba, U and Th. An apparent feature of the anomalous field is that elements metioned above are enrichcd eighcr in the crust or in the mantle, which is thought to be the basis for the metallogenesis or tin poly-mctallic deposits.2. A new rock-forming age 2412 Ma. for the Sibao group is got hcrc by Sm-Nd isochron method dating the mafic-ultramafic whole rocks. In this way, the oldcst stra-ta in the Yangtze Massif is the early Protcrozoic in stead of middle-late Protcrozoic in-ferred before.3. Tha layered basic-ultrabasic intrusions called before are confirmed as a suite of mafic-ultamafic volcanic rocks, of which its part is identified to be komatiite by studieson the rcglonal rock sequence, petrology, rock structures, geochemistry and trace ele-ments.4. The magmatic liquation type Cu-Ni sulfide deposits called before have been proved to be volcanic Cu-Ni deposits associated with pyroxenic komatiite, which is a new type Cu-Ni deposit in China.5. A series or criteria of recognizing tin-bearing graniteis set up by collecting the data on related petrology, mineralogy, geochemistry, trace elements, transitional ele-ments, incompatible elements and rare earth elements. Furthermore, with the criteria the two series of granitoids (granodiorite series and biotite granite series) in the region are well recognized.6. The biotite granite intrusions, emplacemented in two stages during the Xuefeng movement, is a dominant factor for the metallogenesis of tin polymetallic deposits. The biotite granite intrusions were formed through remelting of the crust and show two im-portant contributions to the minerogeneses. Firstly, during formation and evolution, the granite intrusions experienced a strong fractionation and concentrated the scattered tin polymetals into their cupolas, which lay a good fundament for the metallogenesis. Secondly, when the biotite granite intrusions emplacemented, their heating energy made the ground water to form a series of circular systems of hydrothermal brines and then many base metal sulfide deposits were formed.7. The Beidong and other similar granodiorite intrusions have been firmly believed as a classical differential granitoids derived from the mantle for long time. Recently some gelolgists suggest that the granodiorites belong to I type granite, and constitute a pair granitoids with Sanfang, Yuanbaoshan, Pingying S type granite at the margin of Yangtze oldoand. In this paper the suit of granodiorite is prelimnarily proved to be remelt type granite in which the major rock-forming substances are derived from the crust and a few from the mantle by study on petrology, genetic mineralogy, geochemistry, trace elements, rare earth elments and isotopes combining with the re-gional geological evolution and geological chronology. The Sm-Nd isotopic model age of the granodiorite shows a consistency with the Sm-Nd isotopic isochronous age of the Sibao group, which displays the former being born from the latter. The key reason for no mineralizations aroud the granodiorite intrusions is that they experienced very poor differentiation, and that they were too small in volume to form the hydrothermal brine deposits.8. The laminated tourmalite tin mineralization in strataform and lentiform bodies are discoverd in the Sibao group. This new discovery not only moves up tin metallogenic age in China from 800 Ma. to 2412 Ma. but also certificates the multicycle and inheritance of tin mineralization in the region; moreover, it provides an instance for marine exhalative tin mineralization associated with mafic magmatic activity.9. The tin polymetallic deposits related to the Xuefeng biotite granites are studied in this thesis according to the academic idea of metallogenic series. The deposits in the metallgenic series show two kinds of zoning from the intrusive body outward.1) the normal zonning in order of greisen type tin deposit" tourmalite type tin deposit→cassiterite quartz type tin deposit→cassiterite sulfide tin deposit→copper-lead-zinc sulfide deposit→lead-zinc sulfide deposit→antimony deposit, which may be related to the high-level emplacement of the intrusions; 2) the reversed zoning in order of lead-zinc deposit→copper-lead-zinc deposit→tin polymctallic deposit, which may be result from the descending of heat centre of the intrusions with their cold and solidification. The metallogenic series in time can be divided into three metallogenic pe-riods (cassiterite silicate period, cassiterite sulfide period and base metal sulfidr period) and six metallogenic stages.10. As for the metallogenesis in inland, some geologists with the viewpoint of magmatic hydroghermal metallogenesis look upon granite intrusion as an only source of metallogenic substance, the others with the viewpoint of stratabound metallogenesis only look upon granite intrusion as a heat source. In the region it is preliminarily certi-fied that some of metallogenic substances (Sn, W, Cu and ect.) are related to the biotite granite, another (Cu, Pb, Zn, Sb and ect. ) are derived from the host strata (es-pecially the mafic-ultramafic rocks). The hydrothermal solution to form the base met-al sulfide deposits is from meteoric water. Thus it can be seen that there exists the dialectical unity between endogenetic and epigenenic mineralizations in the metallogenic series.11. The conception of metasomatic system is put forward here. The metasomatism and metasomatic phenomena in the region are studied with the academic idea of metasomatic series and formations. The chemical compositional changes, conditions, evolutional directions and final results of various metasomatic daughter-series in the metasomatic network are studied from the point of view of mineralized-altered period taken as meridian and metasomatic series as latitude.12. The minerogenetic environment and compositional evolution of the metallogenic series of tin polymetallic deposits related to biotite granite are studied by the methods of genetic mineralogy, geochemistry of ore, altered rocks, isotopes and in-clusions.13. A new idea for the polymetallic metallogenesis, including the geochemical anomalous field of tin polymetallic elements as a prerequisite, the tetonic movement as a leading role and the strong differential evolution and heating effect of the biotite granite intrusions as a dominant factor, is put forward in this thesis. Furthermore, the metallogenic model of the metallogenic series in the region is set up here.14. A new mineral with Cu, 28.52%, Ni, 64, 81% and Fe, 6.58% (preliminarily named Baotanite) is discovered together with Mr. Zhoukezi.更多还原