吉林白山地区玄武岩中宝石矿床成矿特征

白山市矿产资源丰富,宝石矿床种类繁多,具有十分重要的研究价值及经济意义.本文仅对碱性玄武岩中宝石矿床产出的构造背景及相关联的蓝宝石、橄榄石矿床的形成条件、特征及成矿规律进行探讨.     

河北大麻坪宝石级橄榄石物理化学性质及成因

对河北大麻坪宝石级橄榄石物理化学及宝石学特征进行研究后，初步提出矿床成因模式，对于相似地区的碱性玄武岩地区的橄榄石宝石矿床的勘探有指导意义。     

吉林省大石河橄缆石矿床的产出特征

吉林省大石河玄武岩规模小，并受敦－密大断裂控制。玄武岩中构成宝石的橄榄石产于二辉橄榄岩包体中和少量的捕虏晶中。矿床为碱性玄武岩，以位于大断裂次级构造上为特征。     

吉林省大石河橄榄石矿床的产出特征

吉林省大石河玄武岩规模小，并受敦－密大断裂控制。玄武岩中构成宝石的橄榄石产于二辉橄榄岩包体中和少量的捕虏晶中。矿床为碱性玄武岩，以位于大断裂次级构造上为特征。     

玄武岩型蓝宝石的颜色及找矿方向

目前市场上所销售的蓝宝石,有很大一部分产自以第三纪碱性玄武岩为母岩的次生矿床中.著名的产出国有澳大利亚、泰国、柬埔寨、中国,在老挝和越南也有这种类型的蓝宝石矿床.产自第三纪碱性玄武岩中的蓝宝石,不管属原生矿,还是次生矿,宝石矿物的共同特点是块度较大,颜色较浓,但是在反射光下,一般颜色较深,特别是块度大者几乎见不到蓝宝石色,暗黑色的外表,把美丽的天鹅绒蓝宝石色深深地     

山东蓬莱新生代玄武岩的构造背景及宝石找矿前景

山东蓬莱位于胶东地体北缘中部。板块动力作用形成了前古生代近EW向构造和中生代NE—NNE向走滑断层,侏罗纪以来地幔柱构造作用逐渐加强,地壳伸展减薄,幔源物质上涌,导致新生代碱性玄武岩喷发。碱性玄武岩中普通辉石、镁铝榴石等可作为低档宝石原料。玄武岩的构造背景、喷发形式、火山机构、岩性特征等与昌乐赋蓝宝石的碧玄岩极为相似,经过有针对性的详细调查研究,寻找红、蓝宝石是有希望的。     

靖宇发现兰宝石

吉林省地矿局第四地质调查所在靖宇县河床的砂砾石中发现兰色刚玉经鉴定达到宝石级,填补了我省兰宝石矿产的一项空白。该区为新生代玄武岩区的边缘,火山口发育。主要分布有第三纪船底山橄榄玄武岩、辉斑玄武岩和气孔玄武岩,第四纪下更新世巴里气孔状玄武岩、橄榄玄     

汉诺坝玄武岩的主要特征及其形成的T、P、fo_2条件

汉诺坝玄武岩主要为由拉斑玄武岩系列与碱性玄武岩系列岩石组成的高原玄武岩。喷发时代为晚第三纪,喷发类型为裂隙式。一、玄武岩、巨晶、包体的组成常见的玄武岩种属为石英拉斑玄武岩、橄榄拉斑玄武岩、碱性橄榄玄武岩及碧玄岩,以碱性玄武岩系列较为少见。在碱性玄武岩系列中,常见巨晶及包体。巨晶有镁铝榴石、普通     

鄂西北碱性火山岩型铌矿床榍石矿物学及对铌富集机理的指示

位于南秦岭武当地区的天宝铌矿床是我国典型的碱性火山岩型铌矿床,但其岩浆成因、演化及成矿机理等方面的研究十分薄弱.天宝碱性火山岩主要分为粗面质岩石和碱性玄武岩两大类,两者在空间上紧密共生.在详细的岩(矿)相学及榍石显微结构研究的基础上,利用LA-ICP-MS分析技术对天宝粗面质火山岩中的榍石进行原位U-Pb定年,并利用E...     

吉林省橄榄石宝石矿床分布特征、勘查开发现状及发展远景

本文在野外地质勘查及系统分析前人工作资料的基础上,对吉林省橄榄石宝石矿床区域分布及勘查开发现状进行归纳总结。吉林省橄榄石宝石矿主要分布在吉林省东部,已发现的橄榄石宝石矿床均赋存于新生界新近系上新统船底山组玄武岩中。严格受敦化-密山岩石圈断裂及其次级断裂控制。在找矿方向上应扩大已有矿区勘查范围,加大勘查力度及对省内船底山组玄武岩分布地区做重点勘查工作部署,力求在橄榄石宝石矿找矿方面取得更大的突破。同时对橄榄石宝石矿业发展远景进行探讨。     

Composition and formation settings of the siliceous-volcanogenic complexes of the Nizhneussuriisk segment,Kiselevka-Manoma terrane,West Sikhote Alin

This paper reports new data on the mineralogical-petrographical composition, genetic types of sedimentary rocks, and geochemical features of the volcanic rocks of the Snarsky area of the Nizhneussuriisk segment of the Kiselevka-Manoma accretionary complex, which is developed on the right bank of the lower reaches of the Ussuri River. The Middle Jurassic-Aptian sedimentary rocks of the area are represented by pelagic radiolarian cherts, semipelagic siliceous-clayey deposits, subordinate shallow limestones, volcanomictic conglomerates, and turbidite sandstones. The basalts of the area are represented by alkaline basalts resembling within-plate ocean-island basalts and N-MORB-type tholeiitic basalts. Rock associations of two physicogeographical and geodynamic settings are distinguished: the pelagic setting with within-plate alkaline volcanic rocks and the hemipelagic one with volcanic edifices of spreading basalts.     

A classification of gem corundum deposits aimed towards gem exploration

This classification of gem corundum (ruby and sapphire) deposits takes into consideration petrographic data, and the mode of genesis of the deposits. It is aimed at being practical and useful in the field, particularly for prospecting purposes.Deposits are classified into primary and secondary deposits. Primary deposits include igneous and metamorphic deposits. Igneous gem corundum deposits are rare and include sapphire-bearing syenites from Kenya. Emphasis is put on metamorphic deposits, that are subdivided into metamorphic s.s., metasomatic, and anatectic deposits. Many gem corundum deposits result from metasomatic processes. Small-scale metasomatism mostly involves desilication reactions between silico-aluminous rocks (pegmatites, gneisses, etc) and silica-poor rocks (ultramafites, meta-carbonates), and leads to the formation of limited-size deposits. Large-scale (diffuse) metasomatism is usually more difficult to characterize, and therefore is not separated from isochemical metamorphism in this classification. In metamorphic deposits, gem corundum results from transformation of an Al-rich and/or Si-poor protolith. Such deposits include ruby-bearing mafic granulites, ruby-bearing meta-limestones, and ruby/sapphire-bearing gneisses and granulites. An intermediate category includes anatectic deposits. Secondary deposits encompass sedimentary and volcanic (xenoclastic) occurrences. In sedimentary deposits, gem corundum occurs as clasts originating from other lithologies. In volcanic deposits, gem corundums are xenocrysts that have a range of origins.The proposed classification outlines geological environments favorable to the crystallization and distribution of gem corundum, thus facilitating prospecting and mining of this gemstone.     

山西新生代汉诺坝玄武岩成因探讨

根据区域地质调查资料,对山西新生代汉诺坝玄武岩的4个火山洼地、7条剖面进行研究。各个火山旋回底部先出现拉斑玄武岩,向上变为碱性玄武岩,岩石均富集大离子亲石元素和轻稀土元素。由东向西,火山喷发时间由早到晚,岩浆活动由弱到强,拉斑玄武岩减少,碱性玄武岩增多,亚碱性玄武岩的稀土元素和微量元素丰度降低,碱性玄武岩的稀土元素和微量元素丰度升高。在原始地幔标准化微量元素蛛网图上,亚碱性玄武岩具Nb、Ta负异常(槽)或呈双峰式,为岛弧玄武岩; 碱性玄武岩呈“隆起”状,类似于洋岛玄武岩(OIB)。山西汉诺坝玄武岩是板块俯冲与地幔柱联合作用的结果,以地幔柱成因为主,板块俯冲成因为辅。亚碱性玄武岩向碱性玄武岩转变,可能代表玄武岩以板块俯冲成因为主转为以地幔柱成因为主; 碱性玄武岩由钾质向钠质变化、亚碱性玄武岩向富铁镁演化,可能分别代表地幔柱向浅、板块俯冲向深的演化过程。     

U–Pb age and origin of gem zircon from the New England sapphire fields,New South Wales,Australia

Chemical compositions and geochronological data utilising the laser ablation ICP-MS technique are presented for zircon megacrysts found in alluvial gem corundum deposits associated with Upper Cretaceous–Cenozoic alkali basalts in the Inverell district-New England field, New South Wales, eastern Australia. Three localities, Kings Plains, Swan Brook and Mary Anne Gully, produce gem-quality transparent dark brown and yellow zircon megacrysts, mostly under 10 mm in size. Although brown zircon shows relative enrichment in Hf and REE, there are no differences in relative transition metal concentrations between the colours. Chemical homogeneity within a single crystal indicates stable crystallisation conditions. The ²⁰⁶Pb/²³⁸U age of zircon megacrysts from these three localities define older and younger groups of 216–174 Ma and 45–37.7 Ma, respectively. The ?_Hf values of zircon megacrysts from Kings Plains show +7.51±0.34 in the older group and +10.72±0.31 in the younger group. Swan Brook zircons give +11.54±0.47 and +8.32±0.58, and Mary Anne Gully zircons are +13.67±0.63 and +8.50±0.48, respectively. These zircons from New England alluvial gem deposits have two main formational events around Upper Triassic–Lower Jurassic and Eocene episodes. Most originated from lithospheric mantle and all were brought-up by later host basaltic magmas.     

北大巴山与志留纪火山作用相关的碳酸盐岩沉积学特征及形成环境

生物碎屑灰岩、生物礁是造山带内最为常见的岩石类型之一,它们可以形成于多种构造环境。研究这些岩石组合的结构组成及生物赋存状态可为古地理恢复及造山带演化提供依据。分布于北大巴山地区与富TiO2碱性火山岩紧密相关的碳酸盐岩组合长期以来被认为是被动陆缘台地相组合。该套碳酸盐岩组合主要由生物礁、生物碎屑灰岩、砂屑灰岩、泥质灰岩、角砾灰岩共同构成。砂屑灰岩及生物灰岩中常伴随有薄层凝灰岩夹层;同时这些碳酸盐岩中富含不同比例的火山碎屑成分,发育粒序层理、平行层理、波纹斜层理和滑塌构造。生物碎屑灰岩通常与凝灰质砂岩、泥岩构成韵律层,火山质碎屑在类岩石中主要表现为粒径0.5~3 mm的棱角状—次棱角状玄武岩和凝灰岩碎屑,具有近源沉积特征;生物礁中通常出现1~2.5 cm棱角状—次棱角状玄武岩碎屑,且在生物礁之间的砂岩夹层中含有丰富的0.5~1 mm的次圆状玄武岩碎屑;砂屑灰岩中含有棱角状—次棱角状玄武岩和辉石两类碎屑,其中辉石碎屑粒径通常为1~2 mm,同时该类岩石中还含有丰富的黄铁矿,这些黄铁矿通常因其粒径变化而发育粒序结构特征。角砾状灰岩可分别由砂屑灰岩、生物礁及生物碎屑灰岩构成,也可由三者共同构成,玄武岩碎屑仅出现于角砾状生物礁灰岩中。这些碳酸盐岩中的生物化石具有曾经历过明显的搬运改造特征,其中生物碎屑灰岩和砂屑灰岩中的化石碎屑以次圆状为主,生物礁中的生物化石平行于砂岩夹层分布且发生不同程度的压扁和挤压变形,岩石中普遍发育滑塌沉积构造。这些特征共同表明,该套碳酸盐岩与下伏的碱性玄武岩形成密切相关,二者共同构成了与现代大洋中典型洋岛/海山相一致的结构特征,且这些碳酸盐岩多沿着下伏玄武岩的周边沉积,具有深水—斜坡环境的沉积组合,同时因其中所包含的生物化石经历了一定距离搬运作用而发生再沉积,进一步表明这些生物发育时代可能要略微早于该套火山—沉积组合的形成时代。     

Mantle Plumes and Their Geologic Manifestations

This paper interprets the conditions of plume formation with a focus on interpretations of origin at the core-mantle boundary. We also discuss important geological manifestations including formation of alkaline-basalt oceanic islands, kimberlite pipes, and plateau-basalt fields. The paper concentrates on the Siberian traps that formed between 249 and 245 Ma, one of the world's largest known plateau-basalt fields, and on the magmatic zonation and ore mineralization associated with the field and that are interpreted as forming from a Siberian mantle plume. One part of the field consists of undifferentiated low-K tholeiite basalts in the Tunguska syncline and contains only minor associated ore deposits. Major, unique Cu-Ni and PGE deposits are associated with differentiated alkaline basalt and with mafic-ultramafie intrusions in the northwestern Siberian platform. Angara-Ilim-type magnetite deposits occur in the southern part of the plateau-basalt province and are related to interaction of mafic magmas with overlying carbonate and evaporite sedimentary rocks. Permian and Triassic alkaline granitoid and bimodal magmatic rocks occur in fold-and-thrust belts that frame the southern, southwestern, and northwestern margins of the main trap area. The paper also presents new geochemical and geochronological data for A-granites for the Taymyr region that are synchronous with traps. For both the southern and northern framing areas, porphyry Cu deposits interpreted as derived from a mantle-crust system are associated with subalkaline and alkaline granitoids.     

CHARACTERISTICS OF VOLCANIC ROCKS AND ITS TECTONIC SETTING IN WESTERN PART OF LAZHULONG-JINSAJIANG STRUCTURAL BELT

CHARACTERISTICS OF VOLCANIC ROCKS AND ITS TECTONIC SETTING IN WESTERN PART OF LAZHULONG-JINSAJIANG STRUCTURAL BELT     

Mineral inclusions in sapphire from the basalt-related deposit in Bo Phloi,Kanchanaburi, western Thailand: indication of their genesis

The Bo Phloi gem field in Kanchanaburi Province, Western Thailand, is closely associated with Cenozoic basalts. Blue and yellow sapphire, black spinel, and minor zircon have been mined for over three decades. The mineral inclusions observed in sapphire samples are alkali feldspar, nepheline, hercynitic spinel, zircon, manganiferous ilmenite, silica-rich enstatite, almandine–pyrope garnet, monazite, calcite, sapphirine, biotite–phlogopite mica, and staurolite. Based on their geochemical affinity, these mineral inclusions can be categorized into two main groups: felsic alkaline and contact-metamorphic, which appear to have originated from different processes. These inclusions provide new evidence for proposing a bimodal genetic model. Felsic alkaline origin is evidenced by the occurrence of a felsic alkaline inclusion suite and the REE geochemistry of sapphire-associated zircon, which indicates that most of the sapphires crystallized from a high-alkali felsic melt (probably, in the lower crust). Contact-metamorphic origin is evidenced by the presence of a contact-metamorphic inclusion suite, suggesting that some of these sapphires might also have originated from metasomatized crustal rocks and a contaminated melt along the contact zone of a basaltic intrusion (probably, in the upper mantle or lower crust).     

四川平武绿柱石宝石成矿地质特征

四川平武产出世界上十分稀少和珍贵的无色透明扁平板状绿柱石宝石。在野外详细调研和系统分析、测试基础上，全国总结和介绍矿床成矿地质环境，绿柱石宝石产出特征，绿柱石宝石矿物学、化学成分、结晶习性及晶体化学、谱学特征、包裹体特征，花岗岩与Be及W,Sn矿化关系和成矿的物理、化学条件。从而，确认该矿床为岩浆期后气成-热液型绿柱石宝石矿床。