Programed oil generation of the Zubair Formation, Southern Iraq oil fields: results from Petromod software modeling and geochemical analysis

1D petroleum system modeling was performed on wells in each of four oil fields in South Iraq, Zubair (well Zb-47), Nahr Umr (well NR-9), West Qurna (well WQ-15 and 23), and Majnoon (well Mj-8). In each of these fields, deposition of the Zubair Formation was followed by continuous burial, reaching maximum temperatures of 100°C (equivalent to 0.70%Ro) at depths of 3,344–3,750 m of well Zb-47 and 3,081.5–3,420 m of well WQ-15, 120°C (equivalent to 0.78%Ro) at depths of 3,353–3,645 m of well NR-9, and 3,391–3,691.5 m of well Mj-8. Generation of petroleum in the Zubair Formation began in the late Tertiary, 10 million years ago. At present day, modeled transformation ratios (TR) indicate that 65% TR of its generation potential has been reached in well Zb-47, 75% TR in well NR-9 and 55-85% TR in West Qurna oil field (wells WQ-15 and WQ-23) and up to 95% TR in well Mj-8, In contrast, younger source rocks are immature to early mature (<20% TR), whereas older source rocks are mature to overmature (100% TR). Comparison of these basin modeling results, in Basrah region, are performed with Kifle oil field in Hilla region of western Euphrates River whereas the Zubair Formation is immature within temperature range of 65–70°C (0.50%Ro equivalent) with up to 12% (TR?=?12%) hydrocarbon generation efficiency and hence poor generation could be assessed in this last location. The Zubair Formation was deposited in a deltaic environment and consists of interbedded shales and porous and permeable sandstones. In Basrah region, the shales have total organic carbon of 0.5–7.0 wt%, Tmax 430–470°C and hydrogen indices of up to 466 with S2?=?0.4–9.4 of kerogen type II & III and petroleum potential of 0.4–9.98 of good hydrocarbon generation, which is consistent with 55–95% hydrocarbon efficiency. These generated hydrocarbons had charged (in part) the Cretaceous and Tertiary reservoirs, especially the Zubair Formation itself, in the traps formed by Alpine collision that closed the Tethys Ocean between Arabian and Euracian Plates and developed folds in Mesopotamian Basin 15–10 million years ago. These traps are mainly stratigraphic facies of sandstones with the shale that formed during the deposition of the Zubair Formation in transgression and regression phases within the main structural folds of the Zubair, Nahr Umr, West Qurna and Majnoon Oil fields. Oil biomarkers of the Zubair Formation Reservoirs are showing source affinity with mixed oil from the Upper Jurassic and Lower Cretaceous strata, including Zubair Formation organic matters, based on presentation of GC and GC-MS results on diagrams of global petroleum systems.     

Lower Eocene phosphorites of the western desert,Iraq

Marine sedimentary phosphorites of Eocene age (Upper Ypresian) are exposed in the extreme west of Iraq within the Dammam Formation. They are associated with limestone and chert, and their deposition seems to have taken place in a shallow marine environment within a structurally controlled basin open to the sea from the northern and western sides only.The studied phosphorites are granular in texture, coarse-grained and cemented by calcite which is occasionally silicified. Bone fragments are present in small amounts. Carbonate-fluorapatite is the only phosphate mineral detected in these phosphorites, with relatively high amounts of the components SO₄^?2, CO₃^?2, F^?1, H₃O¹ and Na¹ substituting in the crystal structure.The Lower Eocene phosphorites of Iraq are part of the Tethyan phosphorite province, and are comparable in many aspects with those of Paleocene and Upper Cretaceous age in the Western Desert of the country.     

Palynomorph and palynofacies indications of age, depositional environments and source potential for hydrocarbons: Lower Cretaceous Zubair Formation, southern Iraq

Assemblages of miospores and dinoflagellate cysts encounterd in core samples three boreholes drilled in southern Iraq an Aptian-mid Albian age-range for the Zubair Formation, the largest oil reservoir in southern Iraq and neighbouring Kuwait. Four types of palynofacies have been identified, and are interpreted to indicate delta top swamp and marsh, delta front, prodelta and marine platform environments respectively. Amorphous matter comprises more than 50% of the organic component of some of the palynofacies in the upper part of the Zubair Formation. The rocks with which they are associated are highly rated as a potential source of liquid hydrocarbons. Those deposits yielding less than this (down to 12%) are considered to have moderate potential.     

Geochemistry of sediments of the Al-Batin alluvial fan,Southern Iraq

The Al-Batin alluvial fan covers a broad area of southern Iraq. It was the main battlefield of two devastating wars in 1991 and 2003, during which huge amounts of depleted uranium (DU) were used. This study aims to assess the geochemistry of this fan sediment including the potential effects of the DU used. Sixty-three samples were collected from sediments including three samples from sediments under tanks attacked by DU ammunition. Major elements were measured by XRF (fusion bead method), whereas ICP-MS was used to measure the trace elements. The results suggest that the most dominant major minerals are in the order of: quartz?>?secondary gypsum?>?calcite?>?feldspar, clay minerals?>?iron oxide, and show abnormal concentrations of Sr, Cr, Ni, and V. This study also determined an area with high concentration of U in the north east part of the fan. Statistical analysis and spatial distribution of important elements suggests that two major factors affect mineral formation. The first factor reflects the influence of minerals in the source area of the sediments (Arabian Shield): quartz, carbonate, clay minerals, feldspars, as well as iron oxides and elevated concentrations of V, Ni, and Cr. The second factor points at authigenic formation of secondary gypsum and celestite and elevated U concentration under the control of a hot arid climate and the specific groundwater situation. However, the origin of the sediments is geogenic, while the anthropogenic impact seems to be minor. Spatial distribution of U and the ^235/238U ratio did not show any peaks in the places where tanks have been destroyed. This is contrary to media speculations and some scientific reports about the permanent risks of DU in the area, which creates public concern about the potential risk of living in this area.     

Mineralogy,geochemistry, and ore formation of Nuwaifa bauxite deposit,western desert of Iraq

Nuwaifa Formation is a part of sequence stratigraphy that belongs to the Jurassic system exposed in the western desert of Iraq. The Jurassic system consists of Ubaid, Hussainiyat, Amij, Muhaiwir, and Najmah formations. Each formation is composed of basal clastic unit overlain by upper carbonate unit. Nuwaifa karst bauxite was developed in fossil karsts within the Ubaid Formation in areas where maximum intersection of fractures and faults exist. This bauxitization process affected the upper surface of the Ubaid limestone formation, which directly underlies the Nuwaifa bauxite Formation. Nuwaifa Formation represents karst-filling deposit that consists of a mixture of allochthonous (sandstone, claystone, and mudstone) and autochthonous lithofacies (bauxite kaolinite, kaolinitic bauxite, iron-rich bauxite, and flint clay). Most bauxite bodies occur within the autochthonous lithofacies and are lenticular in shape with maximum thickness ranges from few meters to 35 m and in some place up to 100 m. Petrographically, the bauxite deposit exhibits collomorphic-fluidal, pisolitic, oolitic, nodular, brecciated, and skeletal textures indicative of authigenic origin. Mineralogy boehmite and gibbsite are the only bauxite minerals; the former is dominant in the upper parts of the bauxite profiles, whereas the latter is dominant throughout the lower and middle part of the bauxite. Kaolinite, hematite, goethite, calcite, and anatase occur to a lesser extent. The study bauxites are mainly composed of Al₂O₃ (33–69.6 wt.%), SiO₂ (8.4–42 wt.%), Fe₂O₃ (0.5–15.9 wt.%), and TiO₂ (0.7–6.1 wt.%) with LOI ranging from 13.5 to 19.1 wt.%. Geochemical investigations indicate that the immobile elements like Al₂O₃, TiO₂, Cr, Zr, and Ni were obviously enriched, while SiO₂, Fe₂O₃, CaO, MgO, Zn, Co, Ba, Mn, Cu, and Sr were depleted during bauxitization process. The results of this study strongly suggest that the bauxite deposits of the Nuwaifa Formation are derived from the kaolinite of the Lower Hussainiyat Formation.     

Palynofacies, palaeoenvironment, and source rocks evaluation of Ratawi Formation, Southern Iraq

Palynological analysis were done on 12 rock samples for Ratawi Formation from Rumailah well 131 and eight samples for the same formation from Zubair well 47, South Iraq, to extract sedimentary organic matters. Microscopic examination led to diagnose large numbers of spores, pollen, dinoflagellates (proximat, cavate, and chorate), foraminifera, melanogen, hylogen, and amorphogen. Three palynological facies were determined on the bases of percentages of sedimentary organic matter and palynomorphs from two sections. Analysis of these palynofacies clarified Ratawi Formation as deposited from environments ranging from delta and lagoon (suboxic–dysoxic) to shelf facies (anoxic near the shore–suboxic) with the presence of some layers deposited from semideep open marine environment (bathyal). Organic geochemical analysis of total organic carbon and Rock Eval pyrolysis were done to determine quantity, quality, and degree of maturation of the kerogen. Poor to medium proportion of total organic carbon of kerogen types II and III within a catagenesis stage are recorded in these rocks, and hence, poor hydrocarbon generation could be suggested for these strata.     

1D PetroMod software modeling of the Basrah oil fields, Southern Iraq

1D (Petromod) hydrocarbon charge modeling and source rock characterization of the Lower Cretaceous and Upper Jurassic underlying the prolific Cretaceous and Tertiary reservoirs in the Basra oilfields in southern Iraq. The study is based on well data of the Majnoon, West Qurna, Nahr Umr, Zubair, and Rumaila oil fields. Burial histories indicate complete maturation of Upper Jurassic source rocks during the Late Cretaceous to Paleogene followed by very recent (Neogene) maturation of the Low/Mid Cretaceous succession from early to mid-oil window conditions, consistent with the regional Iraq study of Pitman et al. (Geo Arab 9(4):41–72, 2004). These two main phases of hydrocarbon generation are synchronous with the main tectonic events and trap formation associated with Late Cretaceous closure of the neo-Tethys; the onset of continent–continent collision associated with the Zagros orogeny and Neogene opening of the Gulf of Suez/Red Sea. Palynofacies of the Lower Cretaceous Sulaiy and Lower Yamama Formations and of the Upper Jurassic Najmah/Naokelekan confirm their source rock potential, supported by pyrolysis data. To what extent the Upper Jurassic source rocks contributed to charge of the overlying Cretaceous reservoirs remains uncertain because of the Upper Jurassic Gotnia evaporite seal in between. The younger Cretaceous rocks do not contain source rocks nor were they buried deep enough for significant hydrocarbon generation.     

Hydrochemical and isotopic investigation of groundwater of Al-Batin alluvial fan aquifer,Southern Iraq

Major ions and important trace elements in addition to δ¹⁸O and δ²H were analysed for 43 groundwater samples sampled from the Al-Batin alluvial fan aquifer, South Iraq. The most dominant ions (with respect to molarity) were: Na⁺ > Cl^? > SO₄ ^2? > Ca²⁺ > Mg²⁺ > NO₃ ^? > HCO₃ ^?, with total dissolved solids (TDS) averaging 7855 mg/L. High concentrations were found for the trace elements U, Mo, V, B, Sr, and Cr. This study suggests a hydraulic connection exists near the fan apex between the uppermost part of the Al-Batin aquifer and the underlying Dammam aquifer by means of the Abu-Jir fault system. Except for the effects of extensive irrigation, fertilizer use, and poorly maintained sewers, the groundwater chemistry is mainly controlled by geological processes such as dissolution of evaporites and the enrichment of dissolved ions as a result of the high evaporation and low recharge rate. Furthermore, it is shown that the Kuwaiti fuel–oil burning during Gulf War in 1991 contributed to the enrichment of V and Mo in the studied aquifer. The spatial distribution of most ions appears to generally increase from the south-west towards the north-east, in the direction of groundwater flow. The stable isotopes show heavier values in groundwater with a gradually increasing trend in the direction of groundwater flow due to the decreasing depth to groundwater and thus increasing of evaporation from both groundwater or irrigation return water. Additionally, the stable isotope signature suggests that rainfall from sources in the Arabian Gulf and the Arabian Sea is the major source of recharge for the Al-Batin aquifer. Except for two samples of groundwater, all samples were not suitable for potable use according to the WHO standards. Most of the groundwater is suitable for some agricultural purpose and for livestock water supply. Apart from the high salinity, boron represents the most critical element in the groundwater with respect to agricultural purposes.     

Salinity mapping model and brine chemistry of Mishrif reservoir in Basrah oilfields,Southern Iraq

Cation and anion concentrations and boron isotopic ratio of brines in the Mishrif Formation (U. Campanian-Tuoronian) from North Rumaila, South Rumaila, Majnoon, Zubair, and West Qurna oilfields southern Iraq were investigated. The aims of this study are to define the type, origin of the oilfield waters, and its flow model in the subsurface oil traps. Mishrif brines are characterized by having higher concentrations of sodium (50,500–84,200 ppm), chlorine (102,100–161,500 ppm), and boron (21.9–31.1 ppm) with lower sulfate contents (187–1350 ppm) relative to the modern seawater. Samples have slightly depleted in δ ¹¹B (35.4‰) relative to seawater fall near the seawater intrusion of the diagram Cl/Br Vs δ ¹¹B and occupied the field of evaporated seawater on the diagrams of Cl vs B and 1/Br vs δ ¹¹B. The brine of Na-chloride type is characteristics of the Mishrif reservoir in all oilfields except WQ which defined by facies of Na-Ca-chloride type. A weak acidic brine of a salinity six-time greater than seawater plays a role in generating the formation pressure and controlling the fluid flow. The reservoir rock-fluid interactions were interpreted using boron isotopes which eventually reveal an ongoing dilution process by the present seawater intrusion and injection water used for the secondary production under conditions of high-temperature digenetic reactions. The ¹¹B in the oilfield water is resulted from uptake of the tetrahedral borate after precipitation of calcium carbonate, while ¹⁰B is sourced from the thermal maturation of organic matters.     

Late Wisconsin macrofossil records of desert vegetation in the American Southwest

Until recently, the oldest-known packrat (Neotoma spp.) midden records of desert scrub vegetation were less than 10,500 yr old and were restricted to altitudes below 300 m in the northern Sonoran Desert. Recent discovery of macrofossil assemblages in the Mojave Desert extends the record of desert vegetation back to 14,800 yr ago and to altitudes as high as 910 m. Although xerophytic conifer woodland was widespread in current desert habitats during the Late Wisconsin and early Holocene, the development of extensive desert vegetation was not delayed until the beginning of the middle Holocene. A regional vegetation mosaic of desert scrub and woodland existed at altitudes below 1000 m in the Mojave Desert during the last part of the Late Wisconsin.     

Facies, depositional environment and diagenetic processes of the early Mid-Miocene Jeribe Formation, Central and Southern Iraq

The Jeribe Formation (Early Middle Miocene) in the central and southern Iraq consists mainly of shallow marine carbonates. Many microfacies have been identified: mudstone, wackestone, packstone, and grainstone with seven submicrofacies. Four major depositional cycles were determined. Microfacies developments and their distribution are controlled by cyclicity and relative sea level fluctuations. The Allochems in the Jeribe Limestone Formation are dominated by bioclasts. Peloids, ooids, and intraclasts are less abundant. The fossils are represented by benthonic forams and very rare planktonic forams. Calcite and dolomite are the predominant mineral components of Jeribe Formation. The carbonates of Jeribe have been affected by a variety of diagenetic processes such as compaction, dissolution, cementation, neomorphism, dolomitization, anhydritization, and silicification. By using the lithofacies association concepts, the depositional model of the Jeribe Formation environment was built. The Jeribe was deposited in open to restricted platforms which indicated lagoonal environment with warm and restricted-open circulation and the lower part (in well Hemrin-2) was deposited in foreslope environment.     

Environmental changes in the wetlands of Southern Iraq based on palynological studies

Palynological techniques are useful in reconstructing past environments, especially when other sources of information are lacking. We have embarked on a palynological study of the wetlands in Southern Iraq in an attempt to determine the nature and extent of past plant communities and other conditions prior to the drying of the wetland in the 1990s. Ten 1-m depth cores were collected from selected locations in marshes and shallow open water wetlands in Mesopotamian wetlands of Southern Iraq. Pollen diagrams from three short cores from the Hawizeh wetlands serve as a reference because this site has not been drained. The palynomorphs in these cores were Gramineae, Chenopodiaceae, Typha, Isonandra lanceolata, Bursarea, Artocarpus, Ireantea, Arenga, Crinum, Palmae, Navia, Tofieldia, Ipomorea, Xyris, and Morus. Fungal spores including Polyporisporites, Pluricellaesporites palyadosporites, Fusiformisporites, Spegazzinites indicus, Diporisporites, Plochmopellinites, Lycoperdon, Miliolinites, Dryadosporites constrictus, and Trichothyrites padapakarensis were noteworthy. Charcoal was scattered through the cores and indicate activities associated with human settlements. Many other forms of cuticles, filaments, insects, algae, and foraminifera test linings were also recorded. A second set of pollen samples were analyzed from 160 soil samples from eight cores collected from the wetland area which was dried during the 1990s. These data show a mixture of pollen and spores that could be used to evaluate past vegetation, climatic, and ecological changes. Preliminary results indicated that chenopodiaceous have increased while germinate types have declined which probably reflected desertification and a trend towards a more aeolian landscape during the 1990s. It is hoped that these studies will be useful in establishing conditions of the wetlands prior to destruction and will assist in setting restoration goals in the future. Case studies of one deep borehole (153 m) near Amara city for evaluating late Quaternary history and dig of 3 m depth to evaluate ancient desertification by wetland dryness were taken for correlation and connection with this recent sediment.     

黑河下游额济纳绿洲荒漠植被与地下水位埋深的 定量关系

干旱区植被生长与地下水的依存关系是生态水文地质学研究的热点之一。由于降水稀少,中国西北地区植被的生长发育与地下水的关系极为密切,从大尺度上研究地下水变化的生态效应问题对生态环境的保护和恢复具有重要的意义。借助遥感方法,结合地下水观测数据,在区域尺度上定量地研究了我国黑河下游额济纳绿洲荒漠植被发育与地下水埋深的关系。结果表明:适宜植被生长的地下水埋深范围约为2~5 m,当地下水埋深超过5.5 m时,由于植被根系缺水,不能维持冠层正常生长,几乎没有植被发育。     

RETRACTED ARTICLE: Depositional environments and porosity distribution in regressive limestone reservoirs of the Mishrif Formation,Southern Iraq

Eight subsurface sections and a large number of thin sections of the Mishrif Limestone were studied to unravel the depositional facies and environments. The allochems in the Mishrif Formation are dominated by bioclasts, whereas peloids, ooids, and intraclasts are less abundant. The sedimentary microfacies of the Mishrif Formation includes mudstone, wackestone, packstone, grainstone, floatstone, and rudstone, which have been deposited in basinal, outer shelf, slop followed by shoal reef and lagoonal environments. The formation displays various extents of dolomitization and is cemented by calcite and dolomite. The formation has gradational contact with the underlying Rumaila Formation but is unconformably overlain by the Khasib Formation. The unconformity is recognized because the skeletal grains are dominated by Chaophyta (algae), which denotes the change of environment from fully marine to lacustrine environment. Thus, the vertical bioclast analysis indicates that the Mishrif Formation is characterized by two regressive cycles, which control the distribution of reservoir quality as well as the patterns of calcite and dolomite cement distribution. Mishrif Formation gradationally overlies Rumaila Formation. This was indicated by the presence of the green parts of Chaophyta (algae) as main skeletal grains at the uppermost part of well Zb-47, which refer to lacustrine or fresh water environment. Petrographical study shows that the fossils, peloids, oolitis, and intraclasts represent the main allochem. Calcite and dolomite (as diagenetic products) are the predominant mineral components of Mishrif Formation. Fossils were studied as an environmental age and facial boundaries indicators, which are located in a chart using personal computer programs depending on their distributions on the first appearance of species. Fifteen principal sedimentary microfacies have been identified in the Mishrif Formation, which includes lime mudstone, mudstone–wackestone, wackestone, wackestone–packstone, packstone, packstone–grainstone, grainstone–floatstone, packstone–floatstone, packstone–rudstone, and wackestone–floatstone. Markov chain analysis has been used to study the transitional pattern of different microfacies types vertically in each well and laterally in all wells as a composite section. The vertical analysis indicates that the Mishrif Formation characterized by two regressive cycles, the main one started with basinal or outer shelf environment, slop environment followed by shoal or reefal environment, and ended with a lagoonal environment. The lateral analysis shows the same regressive cycle, and by using the lithofacies association concepts, we built the depositional model of the Mishrif Formation environment.     

Geological Features, Mineralization Types and Metallogenic Setting of the Phlaythong Large Iron Deposit, Southern Laos

<正>The Phlaythong large iron deposit in Shampasak of southern Laos,is located in the Kon Tum microblock(Fig.1A),central-southern part of the Indo-China block,and the geographic coordinate of the central mining area is 14°43′04″N and 106°07′02″E.Intensive tectonic and magmatic activities of multiple periods developed in this region,especially in Mesozoic and Cenozoic,which are closely     

Analysis of NVDI variability in response to precipitation and air temperature in different regions of Iraq,using MODIS vegetation indices

Iraq, the land of two rivers, has a history that extends back millennia and is the subject of much archaeological research. However, little environmental research has been carried out, and as such relatively little is known about the interaction between Iraq’s vegetation and climate. This research serves to fill this knowledge gap by investigating the relationship between the Normalized Difference Vegetation Index (NDVI) and two climatic factors (precipitation and air temperature) over the last decade. The precipitation and air temperature datasets are from the Water and Global Change Forcing Data ERA-Interim (WFDEI), and the NDVI dataset was extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) at 250 m spatial resolution and 16 day temporal resolution. Three different climatic regions in Iraq, Sulaymaniyah, Wasit, and Basrah, were selected for the period of 2001–2015. This is the first study to compare these regions in Iraq, and one of only a few investigating vegetation’s relationship with multiple climatic factors, including precipitation and air temperature, particularly in a semi-arid region. The interannual, intra-annual and seasonal variability for each region is analysed to compare the different responses of vegetation growth to climatic factors. Correlations between NDVI and climatic factors are also included. Plotting annual cycles of NDVI and precipitation reveals a coherent onset, fluctuation (peak and decline), with a time lag of 4 months for Sulaymaniyah and Wasit (while for the Basrah region, high temperatures and a short rainy season was observed). The correlation coefficients between NDVI and precipitation are relatively high, especially in Sulaymaniyah, and the largest positive correlation was (0.8635) with a time lag of 4 months. The phenological transition points range between 3 and 4 month time lag; this corresponds to the duration of maturity of the vegetation. However, when correlated with air temperature, NDVI experiences an inverse relationship, although not as strong as that of NDVI and precipitation; the highest negative correlation was observed in Wasit with a time lag of 2 months (? 0.7562). The results showed that there is a similarity between temporal patterns of NDVI and precipitation. This similarity is stronger than that of NDVI and air temperature, so it can be concluded that NDVI is a sensitive indicator of the inter-annual variability of precipitation and that precipitation constitutes the primary factor in germination while the air temperature acts with a lesser effect.     

西藏拉隆穹窿地质特征和Be-Nb-Ta稀有金属矿化的厘定及其战略意义

拉隆穹窿位于北喜马拉雅片麻岩穹窿带东段,介于康马穹窿和错那洞穹窿中间.在野外地质调查和精细剖面测量基础上,通过详细的构造变形、野外岩石学和矿物学综合研究,发现拉隆穹窿由内向外由三部分组成,依次是核部、滑脱系和盖层.核部主要是一套新生代高分异的淡色花岗岩组合,未见老基底出露;滑脱系主要由一套中高级变质的云母类片岩、和夹于片岩中的大理岩、矽卡岩和变形花岗岩组成,整体属于一条规模较大的韧性剪切带;盖层主要是一套浅变质或未变质的千枚岩、千枚状板岩和粉砂质板岩组成.滑脱系与盖层之间以上拆离断层为界,下拆离断裂在穹窿中还未完全剥露出来,整体以鞘褶皱发育为典型特征.且拉隆穹窿分别经历了由南向北逆冲挤压构造、由北向南伸展剪切构造、成穹构造和近E-W向伸展构造等四期构造变形;其中第二期构造变形在穹窿中发育和保存最好.在变质作用上,拉隆穹窿保存了两类变质作用:一类是围绕穹窿核部呈环带分布的典型巴洛式变质作用,由外向内依次是硬绿泥石-堇青石变质矿物带、石榴石-黑云母变质矿物带、十字石变质矿物带、蓝晶石变质矿物带;另一类是受岩体热烘烤所形成的热接触变质作用,典型的变质矿物有红柱石.穹窿核部花岗岩呈良好的垂向分带特征,从下向上依次是二云母花岗岩、白云母花岗岩、伟晶质花岗岩、钠长石花岗岩和伟晶岩壳/石英壳.在稀有金属成矿方面,拉隆穹窿中共识别出三种矿化类型:矽卡岩型Be-Nb-Ta稀有金属矿、钠长石花岗岩型Be-Nb-Ta稀有金属矿和构造-热液型Cu-Pb-Zn多金属矿,其中拉隆穹窿Be-Nb-Ta稀有金属矿床,特别是钠长石花岗岩型Be-Nb-Ta稀有金属矿的发现,极大地丰富和扩展了北喜马拉雅带稀有金属的成矿类型和成矿潜力;同时在摸清我国关键矿产资源家底、提高关键矿产资源战略统筹能力、发挥其作为大国博弈的重要利器作用等方面具有十分重要的战略意义.