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1.
Geological, methodological, and economic aspects of the production and utilization of petrother mal resources (heat of “dry”
rocks) for electric energy production and heat supply are considered. Possibility of the utilization of natural fracture zones
or artificial fissure zones, which are created by hydraulic fracturing of underground rock massifs, is noted. Application
of new tools for drilling deep wells makes the petrochemical energy competitive relative to both other types of renewable
resources and traditional organic fuel. 相似文献
2.
L. Valenzuela-Vásquez J. Ramírez-Hernández J. Reyes-López A. Sol-Uribe O. Lázaro-Mancilla 《Environmental Geology》2006,51(1):17-27
Anomalous high fluoride concentration up to 7.59 mg/dm3 is found in groundwater from “La Victoria” area. This water is used to supply drinking water to Hermosillo City, Sonora. Geochemistry of groundwater, relationship between physicochemical parameters, hydrogeology and geologic setting were correlated to define the origin and the geochemical mechanisms of groundwater fluorine enrichment. High fluoride concentration is associated with high bicarbonates, pH and temperature, and it decreases toward the west and south of the area. Fluoride is in negative correlation to calcium concentration. Sodium sulphate facies of regional deep water flow are related to high fluoride concentration. High electric resistivity rocks associated with granites from the Sierra Bachoco basement might be the deep source of fluoride. Outcropping of Sierra Bachoco in the west causes upward regional flow. Groundwater of longer residence time can be pumped there. The anomalous area is restricted to “La Victoria” because calcareous paleozoic rocks outcrop to the south. 相似文献
3.
张启厚 《中国地球化学学报》1999,18(2):172-179
The Dachang antimony deposit in Qinglong,Guizhou Province,is strictly controlled by the “Dachang Layer” which is a complex altered rock occurring at unconformity between the Permian Emeishan basalt and the Maokou limestone.Based on the studies of the hanging-and foot-wall rocks,the trace elements and REE contents of the rocks and ores and heavy placer minerals in the basalt,this paper is focused on the relations between these data and the “Dachang Layer”and its hanging- and oot-wall rocks.The author pointed out that the “Dachang Layer” and basalt are the source-beds of antimony;ilmenite and magnetite are the major mineral carriers of antimony.In the processes of halmyrosis and burial metamorphism of the “Dachang Layer” an basalt,antimony was mobilized along with the mobilization of iron and was preliminarily concentrated in the“ Dachang Layer”. 相似文献
4.
M. Fontana F. Grassa G. Cusimano R. Favara S. Hauser C. Scaletta 《Environmental Geology》2009,57(4):885-898
In the Rocca Busambra area (mid-west Sicily, Italy), from November 1999 to July 2002, 23 water points including wells and
springs were sampled and studied for their chemical and isotopic compositions. Two rain gauges were also installed at different
altitudes, and rainwater was collected monthly to determine the isotopic composition. The obtained results revealed the Rocca
Busambra carbonate complex as being the main recharge area on account of its high permeability value. From a chemical view
point, two main groups of water can be distinguished: calcium–magnesium–bicarbonate-type and calcium–magnesium–chloride–sulphate-type
waters. The first group reflects the dissolution of the carbonate rocks; the second group probably originates from circulation
within flyschoid sediments. Three water wells differ from the other samples due to their relatively high Na and K content,
which probably is to be referred to a marked interaction with the “Calcareniti di Corleone” formation, which is rich in glauconite
[(K, Na)(Fe3+, Al, Mg)2(Si, Al)4O10(OH)2]. In accordance with WHO guidelines for drinking water (2004), almost all the samples collected can be considered drinkable,
with the exception of four of them, whose NO3
−, F− and Na+ contents exceed the limits. On the contrary, the sampled groundwater studied is basically suitable for irrigation. 相似文献
5.
A sudden disturbance in water level was recorded by hydrographs monitoring wells in the coastal city Dammam, Saudi Arabia
on December 26, 2004. The water level was being recorded from the shallow (1–3 M deep) coastal aquifer at that time. In two
wells, this disturbance was observed ~12 h after the Sumatra earthquake/tsunami event of December 26, 2004. The timing of
this event is synchronous in two wells near the coast, but an inland well away from the coast line did not show any such disturbance.
It is hypothesized that this disturbance, we call it the “shock event”, is resulted by sudden impact of tsunamis traveling
in the Arabian Gulf from southeast toward northwest. As the tsunamis propagated, they suddenly impacted the coastal shallow
groundwater aquifer resulting in the “shock event”. 相似文献
6.
Kuznetsov N. B. Natapov L. M. Belousova E. A. Griffin U. L. O’Relly S. Y. Kulikova K. V. Soboleva A. A. Udoratina O. V. 《Doklady Earth Sciences》2010,435(2):1676-1683
This report presents the first results of U/Pb dating, isotope-geochemical, and geochemical studies of detrital zircons from
the Neoproterozoic clastic rocks of the Southern Timan. Sixty-one zircon grains were treated, including 51 from red-colored
sandstones and 10 grains from aleurosandstones of the Djejim Formation of the southern Chetlas-Djejim zone (Djejim-Parma Hill).
It was found that the U/Pb-ages of zircons from the rocks of the Djejim Formation, varied from ∼2.97 to ∼1.20 Ga. The studies
of microelement composition in 47 grains (of 61 U/Pb isotope ages obtained), on the basis of several empirical regularities
found formerly, show that the detrital zircons had originated from “granites” (22 grains), “diorites” (12 grains), or their
volcanic analogues, or more rarely, from “syenites” and “basites” (5 and 8 grains, respectively). The Lu/Hf isotope system
of zircons allows one to estimate the model ages (T
DMC) of the substrate magmatic rocks being parental to the zircons considered. In particular, Archean zircons are characterized
by ∼2.84–3.36 Ga model ages of magmaforming rocks. For some of the grains, their model ages (∼2.84 Ga) are close to those
of zircons as such (∼2.7–2.8 Ga), which points to the juvenile character of the substrate from which the parent magma of the
zircons treated was fused. For Proterozoic (to Middle Riphean) zircons, the Lu/Hf isotope system allows one to estimate the
model age of the substrate of their parental rocks within ∼2.00–3.36 Ga, which shows that these rocks were formed under the
recycling of the Archean and Early-Proterozoic crust. The ages obtained for detrital zircons, as well as model ages of the
substrate of the corresponding parental magmatic rocks, are quite comparable to the age of crystalline complexes of the ancient
framework of the East European Platform (EEP), formed in the course of the Archean, Early-Proterozoic, and Early-Middle Riphean
tectonomagmatic events. This permits us to conclude that the Neoproterozoic detrital complexes of the Timan were formed owing
to the erosion of earlier Neoproterozoic and Early Precambrian complexes constituting the Neoproterozoic Baltica continent,
presenting complexes of the passive margin of this continent. A variety of ages of detrital zircons from sandstones and aleurosandstones
from the Djejim Formation of Djejim-Parma Hill, and of the estimates of magmatic rocks parental to these zircons, may be characterized
as a Baltic Provenance signal. 相似文献
7.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
8.
Essam E. El-Hinnawi 《Contributions to Mineralogy and Petrology》1973,38(4):339-341
Biaxial calcite grains occur in several Egyptian carbonate rocks. The degree of biaxiality is nearly consistent; the optic
axial angle being in the range of 8–10°. The reasons of this “biaxiality” are discussed and it is urged that this phenomenon
should be considered both in research and teaching. 相似文献
9.
G. Gabert 《Mathematical Geology》1978,10(5):425-432
Based on the results of the Conference on Resource Assessment Techniques of IGCP Project 98 in Loen, Norway, 1976, the importance
of mineral and energy inventories is demonstrated by their long-term objectives which aim at the solution of problems of quantitative
and qualitative mineral and energy reserve and resource assessments, estimates of the exploration potential, supply analysis,
future land-use planning, and national mineral policy. Prior to establishing a mineral and energy inventory it is essential
to clearly define both the long-term and short-term objectives, because they control the scope of an inventory and determine
the approach to and the method of constructing the data base. Only then can questions be answered as to the kind of data required,
the advantages of regional-versus commodity-based inventories, the necessity of computer-processable data files, the availability
of a user-oriented data base management system, and the usefulness of conducting a pilot project. Examples are given for simple
and complex types of mineral and energy inventories. The “Mineral Deposit Inventory” of the Institute for Geosciences and
Natural Resources, Hannover, Federal Republic of Germany, serves mainly as an information and reference system, whereas the
mineral inventory of “Project Manitoba” of the Geological Survey of Canada forms the base for reserve and resource assessment
as well as land-use planning of that province. For developing and industrialized countries alike, mineral and energy inventories
are appropriate tools in planning new exploration activities and decisions on future national mineral policy. Used by the
Regional Mineral Resources Development Centers of ESCAP and ECA, the United Nations economic commissions in Asia and Africa,
these tools could be of great advantage and mutual benefit to the developing countries of those regions.
This paper was presented at the International Geological Correlation Program (IGCP) Project 98: “Standards for Computer Applications
in Resource Studies” held at Taita Hills, Kenya, November 8–15, 1977. 相似文献
10.
M. T. Krupenin A. V. Maslov I. D. Tsybulenko R. A. Nafikov V. G. Petrishcheva 《Lithology and Mineral Resources》2000,35(3):267-277
A property of swelling on heating to yield firm lightweight granules has first been revealed for lowcarbonaceous shales (LCS)
from the Riphean stratotype in the Bashkirian Megaanticlinorium, Southern Urals. These granules possess all technological
properties of “keramzite” or claydite (an artificial, expanded clayey material) and can successfully substitute this material.
Moreover, the procedure of their manufacture, analogous to the manufacture of “shungizite” (an artificial carbonaceous-clayey
material) from Lower Proterozoic clayey rocks of Karelia, is more economical than that for keramzit. Productive beds of the
homogeneous LCS make up extended bodies tens of meters thick. At the present time, they can be used as cover rocks during
the exploitation of the Bakal siderite deposits. The LCS represent fine-grained quartz-chlorite-sericite aggregates (with
variable relationships between the major components), bearing fine-dispersed shungite in amounts of 0.5–1.0%. High-quality
raw material of this kind is characterized by a fine-dispersed admixture of a mixed-layer clayey material bearing montmorillonite
and vermiculite. Geological, lithological, mineralogical, and chemical prognostic criteria have been developed for the shungizite
raw material. It has been concluded that this construction material, new for the Urals, is promising for industrial use 相似文献
11.
Hydrochemistry and Classification of Groundwater Resources of Ishwardi Municipal Area,Pabna District,Bangladesh 总被引:2,自引:0,他引:2
Golzar Hossain M. Farhad Howladar Lutfun Nessa Syed Samsuddin Ahmed Chowdhury Quamruzzaman 《Geotechnical and Geological Engineering》2010,28(5):671-679
The chemical property of groundwater depends largely on the mineralogical composition of the rocks through which the water
has moved and the rate of movement and these characteristics of surface water depend on organic and inorganic reactions, industrial
effluents, rainfall and temperature etc. The underground water tends to contain more dissolved materials than those in surface
water because of their more intimate and longer contact with organic materials of soil and rock particles. The groundwater
of the studied area is dominant of alkaline earth’s (Ca2+ and Mg2+) and weak acids (HCO3
−) which may be classified as Magnesium-Bicarbonate and Calcium Carbonate types. Genetically, the groundwater of the area belongs
to both “Normal Chloride” “Normal Sulphate” and “Normal Carbonate” to “Super Carbonate” group. Based on EC, SAR and RC, the
groundwater of the area varies from good–excellent quality for irrigation purposes with low alkali hazard and medium salinity
hazard. 相似文献
12.
During the Mesozoic, the epicontinental Germanic Basin and the Regensburg Strait the latter being an embayment of the Tethys
Ocean that had subsided into the Moldanubian Zone of the Central European Variscides were filled with terrigenous continental-marine
sediments. Both sediments’ heavy mineral (HM) grains and aggregates have been studied in a drill section in the Wackersdorf
area, SE Germany. The majority of them belong to the (semi)opaque group of Fe–Ti minerals. In Wackersdorf, the entire stratigraphy
of the basin fill, which occurred between the Triassic and the Late Cretaceous, is well exposed. In addition to the chemical
composition of HM, the morphology and texture of zircon, apatite and Fe–Ti compounds have been studied in a provenance-related
mineral classification. Provenance analysis has yielded five discrete source rock lithologies: (1) Moldanubian H-T-metamorphics,
(2) late Paleozoic (sub)volcanic rocks, (3) gneisses of the Tepla-Barrandian unit, (4) ophiolites of the Tepla-Barrandian
unit, (5) silicified shear zones and quartz cores of pegmatites. The detrital minerals include zircon, tourmaline (dravite-schoerl),
apatite, monazite (Ce–Th–La–Nd), xenotime, biotite, rutile, ilmenite, “nigrine” (ilmenite-rutile intergrowth), sphene, amphibole,
staurolite, garnet and spinel (Cr–Mg–Al). Based on the allogenic Ti and Fe minerals, a magnetite-type source area (Eh > 0, near-surface felsic to intermediate (sub)volcanic rocks) was distinguished from an ilmenite-type source area (Eh < 0), deeply eroded crystalline basement rocks (gneiss, granite, shear zones). The latter may be subdivided
into “nigrine –I” (deep) and “nigrine-II” (intermediate) subtypes, according to the level of erosion in the source area. At the Jurassic–Cretaceous transition,
extrabasinal erosion provoked a noticeable variation of allogenic heavy minerals with the incisions of rivers into source
rock lithologies (4) and (5). Uplift and erosion along the western edge of the Bohemian Massif took place contemporaneously
with spreading and closure in the central parts of the adjacent Tethys Ocean. 相似文献
13.
During the late Early Cretaceous, the shallow-water domains of the western Tethys are characterized by the widespread deposition
of Urgonian-type carbonates rich in rudists, corals and other oligotrophic, shallow-marine organisms. In the Helvetic Alps,
the Urgonian occurrences have been dated by ammonite biostratigraphy as Late Barremian and Early Aptian. For the more proximal
occurrences in the western Swiss Jura, a recent age model based on bio-, chemo- and sequence stratigraphy has been proposed,
which allows for an improved correlation with the Helvetic counterparts. In order to corroborate the recently proposed age
model for the Jura, a set of well-preserved rhynchonellids collected from five different lithostratigraphical formations and
members (“Marnes bleues d’Hauterive”, “Marnes d’Uttins”, basal marly layers within the “Urgonien Jaune”, “Marnes de la Russille”,
“Urgonien Blanc”) has been analysed for its strontium–isotope ratios (87Sr/86Sr). In addition, K–Ar dating was performed on well-preserved glauconite grains from two different levels (“Marnes d’Uttins”
and a basal layer within the “Urgonien Jaune”). The correlation of the Sr–isotope data set with a belemnite-based, ammonite-calibrated
reference curve provides an age model which is coherent with recently published ages based on calcareous nannofossil biostratigraphy
and the correlation of trends in chemo- and sequence stratigraphy. K–Ar dating on well-preserved glauconite grains from the
“Marnes d’Uttins” and lowermost part of the “Urgonien Jaune” delivered ages of 127.5 ± 2.3 and 130.7 ± 2.6 Ma, respectively.
Whereas the age of the glauconitic level near the base of the “Urgonien Jaune” is chronostratigraphically meaningful, the
K–Ar age of the “Marnes d’Uttins” appears too young relative to the presently used time scale. This may be related to rejuvenation
of the K–Ar chronometer due to post-depositional Ar loss, most likely during hardground formation. The ages obtained here
confirm the Late Barremian age for the onset of the Urgonian platform, an age which is conform with ages obtained in the Helvetic
Alps and elsewhere along the northern Tethyan margin. 相似文献
14.
Sophie Decrée Étienne Deloule Gilles Ruffet Stijn Dewaele Florias Mees Christian Marignac Johan Yans Thierry De Putter 《Mineralium Deposita》2010,45(7):621-629
The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves.
They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks.
Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs.
The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class
“manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal
mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar–Ar analyses of oxidized Mn ore and
in situ U–Pb SIMS measurements of heterogenite yield Mio–Pliocene ages. The Ar–Ar ages suggest a multi-phase process, starting
in the Late Miocene (10–5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional
uplift. Further oxidation took place in the Pliocene (3.7–2.3 Ma) and formed most of the observed deposits under humid conditions:
Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional
shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in
erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot
slopes. 相似文献
15.
The Neoproterozoic Kolet Um Kharit bimodal metavolcanic rocks, south Eastern Desert, Egypt: a case of enrichment from plume interaction? 总被引:1,自引:0,他引:1
E. S. Farahat 《International Journal of Earth Sciences》2006,95(2):275-287
Neoproterozoic metavolcanic rocks of Kolet Um Kharit (KUKh) in the southern Eastern Desert of Egypt have been traditionally regarded as a bimodal island-arc sequence. However, geological and geochemical arguments presented here make this interpretation doubtful. Geochemically, these rocks are classified into mafic (tholeiitic basalts) and felsic (high-K rhyodacites to rhyolites) groups. Both the KUKh mafic and felsic metavolcanic rocks show similar geochemical characteristics, implying a genetic link. They have comparable trace element ratios, such as Zr/Nb (27–30 vs. 20–36), Y/Nb (5.44–6.25 vs. 5.05–5.9), K/Rb (577–1164 vs. 573–937), Ba/La (4.29–25–9 vs. 11.4–16.2), Nb/Yb (1.82–2.03 vs. 1.76–1.99). Similarly both groups have parallel LREE-enriched patterns (La/YbCN=2.37–2.81 vs. 2.55–3.17); and negative Nb and Ta anomalies (Nb/Lapm=0.51–0.58 vs. 0.45–0.52 and Ta/Lapm=0.51–0.62 vs. 0.49–0.55). The observed negative Nb and Ta anomalies in the KUKh metavolcanic rocks cannot be attributed to crustal contamination or fractional crystallization. These rocks could represent either a remnant of break-up LIP or were derived from an enriched mantle source containing subduction components beneath an intraoceanic back-arc basin. The recognition of the KUKh rocks as derived from an enriched mantle source revives interest in models that involve enrichment from “plume” interaction during the evolution of the Arabian-Nubian Shield. 相似文献
16.
Arun K. Saraf Vineeta Rawat Priyanka Banerjee Swapnamita Choudhury Santosh K. Panda Sudipta Dasgupta J. D. Das 《Natural Hazards》2008,47(1):119-135
Stress accumulated in rocks in tectonically active areas may manifest itself as electromagnetic radiation emission and temperature
variation through a process of energy transformation. Land surface temperature (LST) changes before an impending earthquake
can be detected with thermal infrared (TIR) sensors such as NOAA-AVHRR, Terra/Aqua-MODIS, etc. TIR anomalies produced by 10
recent earthquakes in Iran during the period of Jun 2002–Jun 2006 in the tectonically active belt have been studied using
pre- and post-earthquake NOAA-AVHRR datasets. Data analysis revealed a transient TIR rise in LST ranging 2–13°C in and around
epicentral areas. The thermal anomalies started developing about 1–10 days prior to the main event depending upon the magnitude
and focal depth, and disappeared after the main shock. In the case of moderate earthquakes (<6 magnitude) a dual thermal peak
instead of the single rise has been observed. This may lead us to understand that perhaps pre-event sporadic release of energy
from stressed rocks leads to a reduction in magnitude of the main shock. This TIR temperature increment prior to an impending
earthquake can be attributed to degassing from rocks under stress or to p-hole activation in the stressed rock volume and
their further recombination at the rock–air interface. A precise correlation of LST maps of Bam and Zarand with InSAR-generated
deformation maps also provides evidence that the thermal anomaly is a ground-related phenomenon, not an atmospheric one. 相似文献
17.
Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid
change in rock material from initial properties to soil-like properties. The sensitivity of a rock type against weatherability
is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected
satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles.
The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia.
The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination
of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the
durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher
than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual
inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According
to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower
than approximately 65%, a dry density lower than 2.4 Mg/m3, and values of water absorption higher than 5%. 相似文献
18.
19.
A. P. Kropotkin 《Astronomy Reports》2011,55(12):1132-1143
The basis is laid out for a theory relating various phenomena in the solar atmosphere, including localized concentrations
of magnetic field at the bases of coronal magnetic arches, chromospheric spicules, twisted coronal magnetic flux tubes, and
flows of energy carried by Alfvén waves propagating upward into the corona. The structure of photospheric currents localized
in the vicinity of supergranule boundaries and excited by convective motions is studied. These currents exist primarily in
a “dynamo layer” of sharply enhanced transverse conductivity, which forms in the weakly ionized thermal photospheric plasma
located in the solar gravitational field. The motions of the electrons and ions in this layer have appreciably different characters:
the ions are collisionly driven by the flows of neutral atoms, while the electrons drift in the crossed electric and magnetic
fields. The electric field supporting the current arises due to the polarization of the electrons and ions. This field also
gives rise to Alfvén perturbations that propagate upward into the corona, together with their associated longitudinal currents.
The character of this “loading” makes the system of fields and currents uniquely defined. Moreover, the momentum flux carried
by these Alfvén waves should be transferred to the cool chromospheric gas, facilitating the vertical ejection of this gas
in the form of spicules, as was first proposed in 1992 by Haerendel. 相似文献
20.
M. Z. Glukhovsky 《Geotectonics》2006,40(1):11-24
By the examples of the Siberian Platform and Canadian Shield, it is shown that spatial juxtaposition of Phanerozoic diamond-bearing
kimberlite fields with giant swarms of Precambrian mafic dikes is caused by both systematic and incidental events. The first
of these include (1) origination of mantle plumes and associated lenses of high-temperature mantle melting in the subequatorial
“hot belt” of the early Earth, (2) formation of magma chambers that generated mafic dikes in these asthenospheric lenses,
(3) shear stress, and (4) ultrahigh-pressure metamorphism of igneous and country rocks. As a result, the association of diamond-bearing
high-density mafic and ultramafic rocks was formed under favorable thermal and fluidal conditions. These processes occurred
first in the embryonic (multiplate) Neoarchean tectonic setting at a depth of 40–60 km (present-day elevation marks) and then
at a deeper (100–150 km) level during the transition to the Proterozoic true plate tectonics. These processes left behind
giant swarms of Precambrian mafic dikes, as well as structurally and genetically related deep-seated morphological and density
anomalies. The relatively high position of two lithospheric units of diamond-bearing rocks, each underlain by a thick layer
of the cold mantle, prevented these units from thermal and mechanical erosion during subsequent plate-tectonic stages characterized
by deeper location of asthenospheric layers. The occurrence of clusters of Phanerozoic diatremes in ancient giant swarms of
mafic dikes, as well as the enrichment of pipes in xenogenic diamond-bearing material derived from different levels of the
tectonically delaminated lithosphere, may be attributed to incidental events that controlled the fertility of a relatively
small number of kimberlite pipes. 相似文献