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1.
Sultan Awad Sultan Hatem M. Mekhemer Fernando M. Santos 《Arabian Journal of Geosciences》2009,2(3):199-211
Different geophysical tools such as geoelectric, gravity, and magnetic have been applied to detect groundwater potentiality
and structural elements, which controlled a geometry of the groundwater aquifers in the study area. Nineteen vertical electrical
soundings measured using ABEM SAS 4000 equipment through Schlumberger configuration of AB/2 ranged from 1.5 to 1,000 m; the
quantitative interpretation was carried out using manual and analytical techniques. The results of quantitative interpretation
used to construct six geoelectrical cross-sections indicate that the subsurface sequence of the study area consists of seven
geoelectrical units. These units are Quaternary sand sheet and sand dunes, Quaternary aquifer, marly limestone, clay, sandy
clay, clay with sandstone intercalation, and deep Nubian sandstone aquifer. The isopach map of the Quaternary aquifer exhibits
thickness of the Quaternary aquifer that increased at the northern and southern part (50 m) and decreased at the eastern and
western part (5 m), and the depth of the aquifer increased at the northern part (40 m) and decreased at the central part to
6 m. The isoresistivity map of the aquifer shows a high resistivity at the northern part but the southern part reveals low
resistivity according to the lithology. The water salinity increases in the direction of groundwater flow from 500 to 10,500 mg/l.
The low water salinity is due to direct recharge from El-Sheikh Zayed Canal, which supplied fresh water to this area. Sixty-five
gravity stations were measured using Auto-Grav gravity meter; different gravity corrections were applied on raw data. The
corrected gravity values were plotted to represent a Bouguer anomaly map; the residual gravity anomaly map was used for delineation
of the fault elements. The area was dissected by different fault elements of trends NW–SE, NE–SW, and E–W. In addition, 65
ground magnetic stations were measured at the same sites of gravity stations. The results of magnetic interpretation indicate
that the depth of the basement is shallow at the western and southern parts of the area (4,500 m), but the central part exhibits
greater depth of 7,900 m.
الملخص العربي طرق جيوفيزيقية مختلفة مثل الكهربية الأرضية, التناقلية الأرضية والمغناطيسية الأرضية تم تطبيقها لتحديد إمكانية تواجد المياه الجوفية والتراكيب الجيولوجية التي تتحكم في إبعاد وهندسة الخزان الجوفي في منطقة الدراسة. تسعة عشر جسة كهربية عمودية تم قياسها باستخدام جهاز من شركة (ِ ABEM) ساس 4000 من خلال تشكيل شلمبرجير بمسافة بين القطبين أب /2 تبدأ من 1.5 متر حتى 1000 متر, التفسير الكمي تم علي البيانات باستخدام التفسير اليدوي والتحليلي. نتائج التفسير الكمي تم استخدامها لتشييد ست قطاعات جيوكهربية والتي أوضحت أن التتابع التحت سطحي لمنطقة الدراسة يتكون من سبعة وحدات جيوكهربية. هذه الوحدات هي صفائح من الرمال والكثبان الرملية للعصر الرباعي, الخزان الجوفي الرباعي, حجر جيري مارلي, طفلة, طفله رمليه, طفله متداخلة مع الرمل والخزان الجوفي النوبي. خريطة السمك للخزان الجوفي الرباعي تظهر أن سمك الخزان الجوفي الرباعي يزيد عند شمال وجنوب منطقة الدراسة (50 متر) ويقل عند الجزء الشرقي والغربي (5 متر). وعمق هذا الخزان الجوفي الرباعي يزيد عند الجزء الشمالي (40 متر) وينقص عمق الخزان الرباعي عمد وسط المنطقة (6 متر). خريطة المقاومة الحقيقية للخزان الجوفي الرباعي تبين أن المقاومة تزيد عند الجزء الشمالي وتقل المقاومة عند الجزء الجنوبي من منطقة الدراسة بناءا علي التكوين الصخري للطبقات. ملوحة المياه الجوفية تزيد في اتجاه سريان المياه من 500 مليجرام/لتر إلي 10500 مليجرام/لتر. نقص الملوحة المياه ناتج عن التسرب المباشر من قناة الشيخ زايد والتي تعتبر مصدر المياه العزبة في منطقة الدراسة. خمس وستون محطة تثاقيلية أرضية تم قياسها باستخدام اوتو-جرافميتر, العديد من تصحيحات الجاذبية الأرضية نم تطبيقها علي البيانات الأصلية. قراءات الجاذبية الأرضية المصححة تم رسمها علي خريطة لتمثل شاذات البوجير وتم استخدام خريطة الشاذات المحلية لتجديد التراكيب الجيولوجية (الفوالق). حيت أوضحت الدراسة أن المنطقة تأثرت بعده فوالق باتجاهات مختلفة مثل شمال غرب- جنوب شرق, شمال شرق-جنوب غرب وشرق-غرب. نتيجة تفسير بيانات المغناطيسية الأرضية أظهرت أن عمق ضجور القاعدة تكون ضحلة عند الجزء الغربي والجنوبي (4500 متر) وتكون ضجور القاعدة عميقة (7900 متر) عند الجزء الأوسط من منطقة الدراسة.相似文献
2.
A. M. B. Moufti 《Arabian Journal of Geosciences》2009,2(1):1-17
A detailed ore microscopic study strengthened by fire assay data of Al Wajh stream sediments (Wadi Al Miyah, Wadi Haramil
and Wadi Thalbah) in northwestern Saudi Arabia shows economic concentrations of gold in the silt fraction (40–63 μm). However,
particles of extremely fine “dusty” gold (≤40 μm in size) were also identified in most stations as independent grains. The
maximum gold content in the samples of Wadi Al Miyah is 13.61 wt%, which is reported for the heavy fraction (<40 μm). Maximum
gold content in the heavy fractions of Wadi Haramil stream sediments amounts 6.90 g/t Au in a relatively coarse fraction (63–125 μm).
It appears that the most fertile heavy fraction in gold among the analysed samples are those from Wadi Thalbah that have the
highest index figure, which makes the placer gold in them more profitable from the economic point of view. The gold content
in the heavy fractions of samples from Wadi Thalbah is economically high lying in the range 6.27–28.83 g/t Au, except for
a sample collected at the upstream with 0.77 g/t Au. Al Wajh stream sediments (including the beach light and black sands)
are also rich in Fe–Ti oxides, rutile and zircon, whereas monazite and thorite are much lesser. Mineral chemistry of magnetite
indicates a distinct titanomagnetite variety (with 3.85 wt% TiO2) which is consistent with the ore microscopic investigation. The titanomagnetite is V- and Cr-free, which indicates derivation
from a more felsic source than a mafic one. No traces of U were found in zircon that sometimes bears up to 2.74 wt% Hf2O3. Chemical analyses of monazite show typical common contents of rare earth elements such as La, Ce, Nd and Sm. Thorite is
either U-free or uranothorite varieties where the latter contains up to 31.79 wt% UO2. One of the U-free thorite grains is Y-bearing and contains 7.13 wt% Y2O3.
كيميائية المعادن من التحليل التقديري الناري لرسوبيات الوديان في منطقة الوجه- شمال غرب المملكة العربية السعودية
توضح الدراسة المجهرية للخامات المعدنية والتي تعضدها بيانات التحليل التقديري الناري لرسوبيات الوديان بمنطقة الوجه (وادي المياه، وادي حرامل، وادي ثلبة) في شمال المملكة العربية السعودية، أن هناك تركيزات اقتصادية للذهب في كسرة الغرين التي يتراوح حجمها من 40 إلى 63 ميكرومتر. في معظم الحالات المدروسة تم رصد حبيبات من الذهب الطليق متناهية الصغر (أقل أو تساوي 40 ميكروميتر). كما اتضح أيضا أن أعلى محتوى لفلز الذهب وجد في القطفات المعدنية الثقيلة دقيقة الحجم المأخوذة من وادي المياه والتي تقدر 13.61 جرام/الطن. أما المحتوى الأعلى في القطفات المعدنية الثقيلة الأكبر نسبيا في الحجم (تتراوح من 63 إلى 125 ميكروميتر) المأخوذة من الرواسب الوديانية بوادي حرامل يصل إلى 6.90 جرام/طن. ويبدو أن القطفات الثقيلة لرسوبيات وادي ثلبة الوديانية هي الأخصب من حيث محتوى الذهب وتلك العينات لها شكل مميز مما يجعل ذهب المراقد بذلك الوادي ذو ربحية مشجعة وذلك من الناحية الاقتصادية. وتتراوح التركيزات الاقتصادية للذهب في عينات وادي ثلبة بين 6.27 - 28.83 جرام/طن باستثناء عينة وحيدة تم تسجيل كمية ذهب بها لا تتعدى 0.77 جرام/طن. عينات الرواسب الوديانية بمنطقة الوجه (بما في ذلك الرمال الشاطئية السوداء والفاتحة اللون) غنية بمعادن خامات أكاسيد الحديد والتيتانيوم والروتيل والزيركون، بالإضافة إلى كميات أقل بكثير من معدني المونازيت والثوريت. وتوضح كيمياء المعادن أن معدن الماجنيتيت غني بالتيتانوماجنيتيت (ماجنيتيت تيتاني به 3.85% من ثاني أوكسيد التيتانيوم) وهو ما أثبتته أيضا الدراسة المجهرية. وهذا الماجنيتيت التيتاني لا يحتوي على عنصري الكروم والفاتيديوم مما يعطي دلالة على أن هذه الصخور فلسية أكثر منها مافية، وأن الزيركون الموجود لا يحتوي على عنصر اليورانيوم بينما يحتوي على أكسيد هافتيوم حتى 2.74%. أما التحاليل الكيميائية للمونازيت فإنها تظهر وجود كميات من العناصر الأرضية النادرة مثل اللانثاتوم والسيريوم والنيوديوم والسماريوم. أما معدن الثوريت فقد تم تسجيل نوعان منه أحدهما لا يحتوي على اليورانيوم أما الآخر فيحتوي على 31.79% من ثاني أوكسيد اليورانيوم. ولقد اكتشف في إحدى حبيبات الثوريت أنها لا تحتوي على اليورانيوم ولكنها تحتوي على عنصر أكسيد الأيتريوم تصل نسبته إلى 7.13%.相似文献
3.
Intraplate basalts of the Eocene–Oligocene Monaro VolcanicProvince (MVP), in southeastern New South Wales, include lower-crustaland refractory to weakly metasomatized upper-mantle xenoliths.Lower-crustal-derived xenoliths appear to be all two-pyroxeneplagioclase granulites (CpxFe:Mg:Ca 0·17–0·56:0·63–0·77:0·28–0·89OpxFe:Mg:Ca 0·39–0·52:1·37–1·47:0·02An72–86 and An48–50) but may also include garnetpyroxenites at depth. Mantle-derived xenoliths are principallyspinel-bearing lherzolites (Fo89·8–90·6CpxFe:Mg:Ca 0·07–0·45:0·70–1·70:0·01–0·94OpxFe:Mg:Ca 0·16–0·19:1·62–1·75:0·01–0·10)but also include amphibole ± spinel-bearing lherzolite(Fo88·7–89·1 CpxFe:Mg:Ca 0·09–0·21:0·61–0·91:0·73–0·93OpxFe:Mg:Ca 0·09–0·31:0·70–1·54:0·03–0·91),spinel-bearing harzburgite (Fo90·5–90·7CpxFe:Mg:Ca 0·08:0·91–0·93:0·74–0·84OpxFe:Mg:Ca 0·16–0·18:1·73–1·79:0·00–0·02),wehrlite, pyroxenite (CpxFe:Mg:Ca 0·08–0·10:0·84–0·90:0·80–0·85OpxFe:Mg:Ca 0·16–0·33:1·51–1·73:0·02–0·03)and rare garnet pyroxenite (GtFe:Mg:Ca 0·83–0·95:1·60–1·70:0·45–0·48CpxFe:Mg:Ca 0·14–0·21:0·69–0·77:0·78–0·86Opx Fe:Mg:Ca 0·31–0·42:1·43–1·56:0·02–0·03)and amphibole–apatite composites. Xenolith textures aregenerally weakly to moderately foliated, a few are mosaic-porphyroblasticand rare samples are veined or highly strained. MVP xenolithsappear to have equilibrated under similar pressure–temperature(P–T) conditions to other southeastern Australian xenolithsequivalent to the South Eastern Australia (SEA) palaeogeotherm.P–T estimates for the MVP suite of xenoliths reveal aheterogeneous lower crust and upper mantle that is thickly underplatedto c. 1·8 GPa or c. 50 km depth. MVP xenolith P–Tdata are compared with those used to derive the SEA palaeogeotherm,which is shown to be in need of revision using more modern geothermometersand geobarometers and new xenolith coexisting mineral data. KEY WORDS: xenolith; petrography; texture; geotherm; Monaro; eastern Australia 相似文献
4.
The structural behavior of stuffed derivatives of quartz within the Li1−
x
Al1−
x
Si1+
x
O4 system (0 ≤ x ≤ 1) has been studied in the temperature range 20 to 873 K using high-resolution powder synchrotron X-ray diffraction (XRD).
Rietveld analysis reveals three distinct regimes whose boundaries are defined by an Al/Si order-disorder transition at x=∼0.3 and a β–α displacive transformation at x=∼0.65. Compounds that are topologically identical to β-quartz (0 ≤ x < ∼0.65) expand within the (0 0 1) plane and contract along c with increasing temperature; however, this thermal anisotropy is significantly higher for structures within the regime 0 ≤ x < ∼0.3 than for those with compositions ∼0.3 ≤ x < ∼0.65. We attribute this disparity to a tetrahedral tilting mechanism that occurs only in the ordered structures (0 ≤ x < ∼0.3). The phases with ∼0.65 ≤ x ≤ 1 adopt the α-quartz structure at room temperature, and they display positive thermal expansion along both a and c from 20 K to their α–β transition temperatures. This behavior arises mainly from a rotation of rigid Si(Al)-tetrahedra about
the <100> axes. Landau analysis provides quantitative evidence that the charge-coupled substitution of Li+Al for Si in quartz
dampens the α–β transition. With increasing Li+Al content, the low-temperature modifications exhibit a marked decrease in
spontaneous strain; this behavior reflects a weakening of the first-order character of the transition. In addition, we observe
a linear decrease in the α–β critical temperature from 846 K to near 0 K as the Li+Al content increases from x=0 to x=∼0.5.
Received: 26 June 2000 / Accepted: 1 December 2000 相似文献
5.
Oxygen isotope systematics of emerald: relevance for its origin and geological significance 总被引：2，自引：0，他引：2
G. Giuliani C. France-Lanord P. Coget D. Schwarz A. Cheilletz Y. Branquet D. Giard A. Martin-Izard P. Alexandrov D. H. Piat 《Mineralium Deposita》1998,33(5):513-519
Oxygen isotopic composition of emerald from 62 occurrences and deposits in the world reveals a wide range in δ18O (SMOW) between +6.2 and +24.7‰. The δ18O-values for each deposit are restricted and can be used to determine the origin of emerald from the world's most important
producers. The δ18O-value of emerald appears to be a fingerprint of its origin, especially for gems of exceptional quality from Colombia (eastern
emerald zone, δ18O = +16.8 ± 0.1‰; western emerald zone, δ18O = +21.2 ± 0.5‰), Afghanistan (δ18O = +13.5 ± 0.1‰), Pakistan (Swat-Mingora districts, δ18O = +15.7 ± 0.1‰), Brazil (Santa Terezinha de Goiás, δ18O = +12.2 ± 0.1‰; Quadrilatero Ferrifero, δ18O = +6.9 ± 0.4‰) and Zimbabwe (Sandawana, δ18O = +7.5 ± 0.5‰). Furthermore, the 18O-composition of emerald appears to be a good marker of its geological environment because the data suggest that host-rock-buffering
of fluid δ18O is considerable during fluid-rock interaction.
Received: 29 January 1998 / Accepted: 25 March 1998 相似文献
6.
Unit-cell dimensions of a natural phlogopite from Pargas, Finland, have been determined in the temperature interval of 27–1050 °C
by X-ray powder diffraction technique. Expansion rates vary discontinuously with temperature with a break at 412 °C. Below
this temperature, the linear expansions (α) for a, b and c axis lengths are 3.74 × 10−5 K−1, 1.09 × 10−5 K−1, and 1.19 × 10−5 K−1, respectively, and above that they are 0.86 × 10−5 K−1, 0.80 × 10−5 K−1, and 1.93 × 10−5 K−1. The volume thermal expansion coefficients are 6.26 × 10−5 K−1 and 3.71 × 10−5 K−1 for low-temperature and high-temperature intervals, respectively. The observed kink in the rate of thermal expansions with
temperature could be due to the different mode of structural changes. Thermogravimetric analysis of the sample indicates the
oxidation of iron in the temperature range of 500–600 °C and dehydroxylation as well as decomposition of phlogopite in the
temperature range of 900–1200 °C.
Received: 8 September 1998 / Accepted: 28 February 2000 相似文献
7.
In situ x-ray data on molar volumes of periclase and tungsten have been collected over the temperature range from 300 K to melting.
We determine the temperature by combining the technique of spectroradiometry and electrical resistance wire heating. The thermal
expansion (α) of periclase between 300 and 3100 K is given by α=2.6025 10−5+1.3535 10−8 T+6.5687 10−3 T−1−1.8281 T−2.
For tungsten, we have (300 to 3600 K) α=7.862 10−6+6.392 10−9 T.
The data at 298 K for periclase is: molar volume 11.246 (0.031) cm3, α=3.15 (0.07) 10−5 K−1, and for tungsten: molar volume 9.55 cm3, α=9.77 (10.08) 10−6 K−1.
Received: July 18, 1996 / Revised, accepted: February 14, 1997 相似文献
8.
Mobility of components in metasomatic transformation and partial melting of gneisses: an example from Sri Lanka 总被引：2，自引：1，他引：1
L. L. Perchuk O. G. Safonov T. V. Gerya B. Fu D. E. Harlov 《Contributions to Mineralogy and Petrology》2000,140(2):212-232
Reaction textures, fluid inclusions, and metasomatic zoning coupled with thermodynamic calculations have allowed us to estimate
the conditions under which a biotite–hornblende gneiss from the Kurunegala district, Sri Lanka [hornblende (NMg=38–42) + biotite (NMg=42–44) + plagioclase + quartz + K-feldspar + ilmenite + magnetite] was transformed into patches of charnockite along shear
zones and foliation planes. Primary fluid inclusion data suggest that two immiscible fluids, an alkalic supercritical brine
and almost pure CO2, coexisted during the charnockitisation event and subsequent post-peak metamorphic evolution of the charnockite. These metasomatic
fluids migrated through the amphibolite gneiss along shear zones and into the wallrock under peak metamorphic conditions of
700–750 °C, 5–6 kbar, and afl
H2O=0.52–0.59. This resulted in the formation of charnockite patches containing the assemblage orthopyroxene (NMg=45–48) + K-feldspar (Or70–80) + quartz + plagioclase (An28) in addition to K-feldspar microveins along quartz and plagioclase grain boundaries. Remnants of the CO2-rich fluid were trapped as separate fluid inclusions. The charnockite patches show the following metasomatic zonation patterns:
– a transition zone with the assemblage biotite (NMg= 49–51) + hornblende (NMg = 47–50) + plagioclase + quartz + K-feldspar + ilmenite + magnetite;
– a KPQ (K-feldspar–plagioclase–quartz) zone with the assemblage K-feldspar + plagioclase + orthopyroxene (NMg=45–48) + quartz + ilmenite + magnetite;
– a charnockite core with the assemblage K-feldspar + plagioclase + orthopyroxene (NMg = 39–41) + biotite (NMg=48–52) + quartz + ilmenite + magnetite.
Systematic changes in the bulk chemistry and mineralogy across the four zones suggest that along with metasomatic transformation,
this process may have been complicated by partial melting in the charnockite core. This melting would have been coeval with
metasomatic processes on the periphery of the charnockite patch. There is also good evidence in the charnockitic core that
a second mineral assemblage, consisting of orthopyroxene (NMg= 36–42) + biotite (NMg=50–51) + K-feldspar (Or70–80) + quartz + plagioclase (An28–26), could have crystallised from a partial melt during cooling from 720 to 660 °C at decreasing afl
H2O from 0.67 to 0.5. Post-magmatic evolution of charnockite at T < 700 °C resulted in fluids being released during the crystallisation
of the charnockitic core. These gave rise to the formation of late stage rim myrmekites along K-feldspar grain boundaries
as well as late stage biotite, cummingtonite, and carbonates.
Received: 15 September 1999 / Accepted: 8 June 2000 相似文献
9.
Summary Fe-Ti-P-rich rocks (FTP) are unusual with respect to their mineralogy and bulk composition. Varieties of these rocks are mostly
related to Proterozoic massif-type anorthosites and to a lesser extent to the upper parts of mafic-ultramafic intracratonic
layered complexes and other igneous rock suites. We present results on the geology, mineralogy and geochemistry of a new occurrence
of FTP, associated with mafic rocks in the northwestern part of Iran. The Qareaghaj mafic-ultramafic intrusion (QMUI) is a
small igneous body situated between Palaeozoic sedimentary rocks and a Precambrian low grade metamorphic complex. The QMUI
is composed mainly of non-mineralized mafic and apatite- and Fe-Ti oxide-rich ultramafic rocks. The mafic rocks, mainly coarse-grained
gabbro, microgabbro and amphibolite, have a simple mineral assemblage (plagioclase + clinopyroxene + ilmenite) and based on
field observations, mineralogy and chemical composition are comagmatic. The ultramafic rocks with high proportion of olivine
(∼40–66 vol.%), apatite (∼0.1–16 vol.%), ilmenite (∼11–19 vol.%) and magnetite (∼2–13 vol.%), have unusual bulk compositions
(e.g., SiO2 ∼ 21–30 wt.%, total iron expressed as Fe2O3
tot ∼ 26–42 wt.%, TiO2 ∼ 5–11 wt.%, MgO ∼ 9–20 wt.%, P2O5 up to 5.1 wt.%, Cr ∼ 40–160 ppm, Ni ∼ 7–73 ppm). The FTP forms numerous sill-like layers, ranging in thickness from ∼5 cm
to few meters. These rocks, totally enclosed in mafic rocks with sharp and concordant contacts, show a magmatic lamination
and follow the general NW–SE trend of QMUI. The apatite-rich ultramafic rocks makes up 90–95% of the total ultramafic outcrops
and contain Mg-poor olivine (Mg# ∼ 40–58) and low-Mg spinel (Mg# ∼ 30–44) in contrast to apatite-poor ones (∼60–63 and ∼43–46,
respectively). Field relationships, mineral compositions and geochemical data suggested that the FTP are not related to the
mafic host rocks. On the contrary, they intruded latter into the gabbros during plastic, high temperature deformation in local
shear zones. Fractional crystallization of P-rich ferrobasaltic parental magma at depth, probably in an open magmatic system,
not far from the QMUI magma chamber, is considered as responsible for the formation of the evolved FTP in QMUI. 相似文献
10.
Almandine–graphite-bearing biotite–cordierite dacitefrom Cerro del Hoyazo, southern Spain, represents erupted magmaproduced by Late Alpine anatexis of high-grade pelitic/quartzo-feldspathicparagneisses. U–Th–Pb ion microprobe analysis ofinherited/detrital zircon cores from the dacite reveals fiveprincipal age groups, 2·8–2·5 Ga, 2·1–1·9Ga, 1·1–0·9 Ga, 650–550 Ma and 350–320Ma, indicating a Gondwana domain provenance. Some of the coresare surrounded by a thin euhedral overgrowth which has the sameage as a suite of sharply euhedral new-grown zircons in thedacite, 6·33 ± 0·15 (t 相似文献
11.
Grain growth kinetics in CaTiO3-perovskite + FeO-wüstite aggregates were studied at the conditions of T = 1223–1623 K, P = 0.1 MPa and P = 200 MPa. Starting samples were fabricated by hot-pressing mechanically mixed powders of CaTiO3 + FeO with FeO = 0%, 1%, 3%, 6%, 10%, 20% and 100% by weight in a gas-medium apparatus at 1323 K and 300 MPa for 5 h. The
increase of grain size (G) of CaTiO3 with time (t) follows a growth law: G
n
−G
n
0 = κ·t(κ=κ0exp(−(Q/RT)). Two grain growth regimes are observed at T < 1523 K and T ≥ 1523 K. For T < 1523 K, the best fits of the data to the growth law yield growth exponents of n = 2.2 ± 0.2, 3.0 ± 0.3 and 3.5 ± 0.3 for samples with FeO = 0%, 3% and 10% respectively. Under these conditions the rate
constants, κ, obey an Arrhenius relation with Q = 206 ± 35 kJ/mol and 385 ± 65 kJ/mol for samples with FeO = 3% and 10%. Grain growth of CaTiO3 becomes sluggish when FeO content exceeds 6%. For T ≥ 1523 K, the best fits of the data to the growth law yield n = 2.5 ± 0.2 for both samples with FeO = 3% and 10%. The activation energies (Q ) were determined as 71 ± 30 kJ/mol and 229 ± 45 kJ/mol for samples with FeO = 3% and 10%, respectively. The TEM observations
show a remarkable difference in the distribution and geometry of FeO below and above 1523 K: nanometer-sized particles of
FeO were observed along CaTiO3 grain boundaries in samples annealed at T < 1523 K. No FeO particles were detected along CaTiO3 grain boundaries in samples annealed at T ≥ 1523 K, but large clusters of FeO particles are observed locally indicating a fast separation of FeO from CaTiO3. Thus we conclude that the slow growth rate of CaTiO3 at T < 1523 K is due to the pinning by FeO particles at grain boundary, and that the change of grain growth kinetics in CaTiO3 at T ≥ 1523 K may relate to the separation of FeO from CaTiO3, which we interpret as due to the phase transformation of CaTiO3 at around 1523 K.
Received: 19 June 1998 / Revised, accepted: 24 March 1999 相似文献
12.
Wang Yong Hou Zengqian Mo Xuanxue Dong Fangliu Bi Xianmei Zeng Pusheng 《Frontiers of Earth Science》2007,1(3):322-332
More than 140 middle-small sized deposits or minerals are present in the Weishan-Yongping ore concentration area which is
located in the southern part of a typical Lanping strike-slip and pull-apart basin. It has plenty of mineral resources derived
from the collision between the Indian and Asian plates. The ore-forming fluid system in the Weishan-Yongping ore concentration
area can be divided into two subsystems, namely, the Zijinshan subsystem and Gonglang arc subsystem. The ore-forming fluids
of Cu, Co deposits in the Gonglang arc fluid subsystem have δD values between −83.8‰ and −69‰, δ18O values between 4.17‰ and 10.45‰, and δ13C values between −13.6‰ and 3.7‰, suggesting that the ore-forming fluids of Cu, Co deposits were derived mainly from magmatic
water and partly from formation water. The ore-forming fluids of Au, Pb, Zn, Fe deposits in the Zijinshan subsystem have δD
values between −117.4‰ and −76‰, δ18O values between 5.32‰ and 9.56‰, and Δ13C values between −10.07‰ and −1.5‰. The ore-forming fluids of Sb deposits have δD values between −95‰ and −78‰, δ18O values between 4.5‰ and 32.3‰, and Δ13C values between −26.4‰ and −1.9‰. Hence, the ore-forming fluids of the Zijinshan subsystem must have been derived mainly
from formation water and partly from magmatic water. Affected by the collision between the Indian and Asian plates, ore-forming
fluids in Weishan-Yongping basin migrated considerably from southwest to northeast. At first, the Gonglang arc subsystem with
high temperature and high salinity was formed. With the development of the ore-forming fluids, the Zijinshan subsystem with
lower temperature and lower salinity was subsequently formed.
Translated from Mineral Deposits, 2006, 25(1): 60–70 [译自: 矿床地质] 相似文献
13.
Taras Nahnybida Sarah A. Gleeson Brian G. Rusk Len I. Wassenaar 《Mineralium Deposita》2009,44(8):837-848
A bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry Cu deposits
in Butte, Montana, USA and Bingham Canyon, Utah, USA. The leachates mostly represent low-salinity magmatic–hydrothermal fluid
inclusions. Their halogen ratios (Br/Cl) of fluid inclusion leachates were determined by ion chromatography, and δ37Cl values of the leachates were measured by continuous-flow isotope ratio mass spectrometry. Br/Cl ratios from early pre-Main
stage and later Main stage veins at Butte range from 0.60 to 1.88 × 10−3 M. Ratios are similar in pre-Main stage veins with sericite bearing selvages and Main stage samples ranging from 0.81 to
1.08 × 10−3 and from 0.92 to 1.88 × 10−3 M, respectively, clustering below seawater (1.54 × 10−3 M) and overlapping mantle values (~1–2 × 10−3 M). Two samples associated with early pre-Main stage potassic alteration yield distinctly lower Br/Cl ratios of 0.60 and
0.64 × 10−3 M. Butte δ37Cl values range from −0.8‰ to −2.3‰ with no significant difference between pre-Main stage and Main stage samples. Br/Cl ratios
for quartz veins from Bingham Canyon range from 0.18 to 3.68 × 10−3 M. Br/Cl ratios from Bingham range above and below previously reported for porphyry copper deposits. In contrast to Butte,
δ37Cl values for Bingham are lower, ranging from −0.9‰ to −4.1‰. In the absence of any processes which can significantly fractionate
chlorine isotopes at high temperatures, we suggest that the porphyry system at Bingham, and to a lesser extent at Butte, have
inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures. 相似文献
14.
Marchesi Claudio; Garrido Carlos J.; Bosch Delphine; Proenza Joaquin A.; Gervilla Fernando; Monie Patrick; Rodriguez-Vega Antonio 《Journal of Petrology》2007,48(9):1813-1840
We present whole-rock major- and trace-element and Nd–Sr–Pbradiogenic isotope data for Cretaceous igneous suites from easternCuba. These rocks are related to the Greater Antilles paleo-islandarc magmatism and have three different igneous styles. Group1 consists of tholeiitic basalts and rare basaltic andesitesthat have normal mid-ocean ridge basalt (N-MORB)-like compositionssimilar to those found in back-arc basin basalts (TiO2 = 1·2–2·9wt%; La/Yb(N) = 0·7–0·9, Th/Nb = 0·06–0·08,and initial 208Pb/ 204Pb = 37·65–37·74).Group 2 comprises basaltic and rare basaltic andesitic subvolcanicdykes with major- and trace-element and isotopic compositionssimilar to those of island arc tholeiites (TiO2 = 0·7–1·4wt%; La/Yb(N) = 0·6–0·9, Th/Nb = 0·06–0·68,and initial 208Pb/ 204Pb = 37·74–38·25).Group 3 is composed of low-Ti (TiO2 = 0·3–0·9wt%) calcalkaline igneous rocks that have an unambiguous subduction-relatedcharacter (La/Yb(N) = 1·1–5·0, Th/Nb = 0·35–1·55,and initial 208Pb/ 204Pb = 37·94–38·39).The parental magmas of the three groups formed by variable meltingdegrees (< 5–25%) of spinel lherzolite, with more depletedmantle sources for Groups 2 and 3 than Group 1. The trace-elementand radiogenic isotope compositions of primitive Group 3 samplesare strongly bimodal. One subgroup of samples is characterizedby low Ta/Yb (0·02–0·03) and Th/La (0·10–0·13),slightly subchondritic Nb/Ta (13·3–17·3),and relatively high initial 206Pb/204Pb (18·57–18·62)and Nd (7·6–9·4). The remaining primitiveGroup 3 samples have higher Ta/Yb (0·06–0·11)and Th/La (0·24–0·32), and highly subchondriticNb/Ta (7·6–9·1), coupled with lower initial206Pb/204Pb (18·24–18·29) and Nd (3·4–5·5).These signatures were induced by two distinct slab componentsthat mainly reflect the contributions of Cretaceous Atlanticmarine and North American continental sediments, respectively.Nb/Ta in the first subgroup was influenced by melting of rutile-bearingsubducted crust, whereas in the second it was inherited fromrecycled continental sediments. The involvement of Atlanticand North American sediments in Cuban Cretaceous magmatism indicatesthat the Proto-Caribbean (North American-Proto Atlantic) lithospheresubducted beneath the Greater Antilles arc during the Late Cretaceous(pre-Campanian), consistent with geotectonic models involvingonset of SW-dipping subduction beneath the Greater Antillespaleo-arc during the Aptian. The variable mantle source depletionand magnitude of the subduction component probably reflect differentsettings across the arc, from the arc front to a back-arc spreadingridge. KEY WORDS: eastern Cuba; Greater Antilles paleo-island arc; mantle source depletion; Nb/Ta fractionation; slab component 相似文献
15.
The Marcona–Mina Justa deposit cluster, hosted by Lower Paleozoic metaclastic rocks and Middle Jurassic shallow marine andesites,
incorporates the most important known magnetite mineralization in the Andes at Marcona (1.9 Gt at 55.4% Fe and 0.12% Cu) and
one of the few major iron oxide–copper–gold (IOCG) deposits with economic Cu grades (346.6 Mt at 0.71% Cu, 3.8 g/t Ag and
0.03 g/t Au) at Mina Justa. The Middle Jurassic Marcona deposit is centred in Ica Department, Perú, and the Lower Cretaceous
Mina Justa Cu (Ag, Au) prospect is located 3–4 km to the northeast. New fluid inclusion studies, including laser ablation
time-of-flight inductively coupled plasma mass spectrometry (LA-TOF-ICPMS) analysis, integrated with sulphur, oxygen, hydrogen
and carbon isotope analyses of minerals with well-defined paragenetic relationships, clarify the nature and origin of the
hydrothermal fluid responsible for these contiguous but genetically contrasted deposits. At Marcona, early, sulphide-free
stage M-III magnetite–biotite–calcic amphibole assemblages are inferred to have crystallized from a 700–800°C Fe oxide melt
with a δ18O value from +5.2‰ to +7.7‰. Stage M-IV magnetite–phlogopite–calcic amphibole–sulphide assemblages were subsequently precipitated
from 430–600°C aqueous fluids with dominantly magmatic isotopic compositions (δ34S = +0.8‰ to +5.9‰; δ18O = +9.6‰ to +12.2‰; δD = −73‰ to −43‰; and δ13C = −3.3‰). Stages M-III and M-IV account for over 95% of the magnetite mineralization at Marcona. Subsequent non-economic,
lower temperature sulphide–calcite–amphibole assemblages (stage M-V) were deposited from fluids with similar δ34S (+1.8‰ to +5.0‰), δ18O (+10.1‰ to +12.5‰) and δ13C (−3.4‰), but higher δD values (average −8‰). Several groups of lower (<200°C, with a mode at 120°C) and higher temperature
(>200°C) fluids can be recognized in the main polymetallic (Cu, Zn, Pb) sulphide stage M-V and may record the involvement
of modified seawater. At Mina Justa, early magnetite–pyrite assemblages precipitated from a magmatic fluid (δ34S = +0.8‰ to +3.9‰; δ18O = +9.5‰ to +11.5‰) at 540–600°C, whereas ensuing chalcopyrite–bornite–digenite–chalcocite–hematite–calcite mineralization
was the product of non-magmatic, probably evaporite-sourced, brines with δ34S ≥ +29‰, δ18O = 0.1‰ and δ13C = −8.3‰. Two groups of fluids were involved in the Cu mineralization stage: (1) Ca-rich, low-temperature (approx. 140°C)
and high-salinity, plausibly a basinal brine and (2) Na (–K)-dominant with a low-temperature (approx. 140°C) and low-salinity
probably meteoric water. LA-TOF-ICPMS analyses show that fluids at the magnetite–pyrite stage were Cu-barren, but that those
associated with external fluids in later stages were enriched in Cu and Zn, suggesting such fluids could have been critical
for the economic Cu mineralization in Andean IOCG deposits. 相似文献
16.
N. S. Bagdassarov 《Physics and Chemistry of Minerals》1999,26(6):513-520
The present study deals with the small strain torsion deformation of MACOR glass-ceramic samples at high temperatures (450–850 °C)
and over a range of low frequencies (20 Hz–5 mHz). The samples of MACOR ceramic consist of 55 vol% randomly oriented, sheet-like
fluorophlogopite mica crystals (∼100–20 μm in planar size, 1–2 μm in thickness) and 45 vol% of isotropic alumino-borosilicate
glass matrix. Measurements of the complex shear modulus show that the sample does not possess the relaxed shear viscosity
even at temperatures above the glass transition temperature of the glass matrix. The maximum of the imaginary component G
′′() of the shear modulus is ∼0.15 of the unrelaxed value G
∞, the relaxation strength Δ≈0.9. The activation energy of the peak of G
′′() is ∼245 kJ mol−1. Using this value of E
a
, the data obtained at various frequencies and temperatures have been reduced to a master curve using the dimensionless variable
ωτ, where ∼0 exp(−E
a
/RT). The internal friction Q−1(ωτ) is ∝1/()0.35−0.4 in the low-temperature high-frequency range (1); passes through a maximum at ∼1 and trends asymptotically to a value Q−1∼0.25–0.30 at ≪1. The behaviour of Q
−1(ωτ) differs from that of a Caputo body by the presence of the resolved peak which may be attributed to the slow mechanical
relaxation of mica crystals due to rotation as well as flexing and bending modes of crystal deformation.
Received: 26 June 1998 / Revised, accepted: 13 January 1999 相似文献
17.
The Archean Shawmere anorthosite lies within the granulite facies portion of the Kapuskasing Structural Zone (KSZ), Ontario,
and is crosscut by numerous linear alteration veins containing calcite + quartz ± dolomite ± zoisite ± clinozoisite ± margarite ±paragonite ± chlorite.
These veins roughly parallel the trend of the Ivanhoe Lake Cataclastic Zone. Equilibria involving clinozoisite + margarite + quartz ± calcite
± plagioclase show that the vein minerals were stable at T < 600 °C, XCO2 < 0.4 at P ≈ 6 kbar. The stabilities of margarite and paragonite in equilibrium with quartz are also consistent with T < 600 °C and XCO2 < 0.4 at 6 kbar. Additional assemblages consisting of calcite + clinochlore + quartz + talc + margarite indicate T < 500 °C with XCO2 > 0.9. Thus, vein formation, while clearly retrograde, spanned a range of temperatures, and fluid compositions evolved from
H2O-rich to CO2-rich. The calcite in the retrograde veins has δ18O values that range from 8.4 to 11.2‰ (average = +9.7 ± 0.9‰) and δ13C values that range from −3.9 to −1.6‰ (average = −3.1 ± 0.6‰). These values indicate that the fluids from which calcite precipitated
underwent extensive exchange with the anorthosite and other crustal lithologies. The fluids may have been initially derived
either from devolatilization of metamorphic rocks or crystallization of igneous rocks in the adjacent Abitibi subprovince.
Vein quartz contains CO2-rich fluid inclusions (final melting T = −57.0 to −58.7 °C) that range in size from 5 to 17 μm. Measured homogenization temperatures (T h) range from −44.0 to 14.5 °C, however for most inclusions (46 of S1), T h = −44.0 to −21.1 °C (ρCO2 ≈ 1.13 to 1.05 g/cm3). At 400 to 600 °C, these densities correspond to pressures of 3.5 to 7 kbar, which is the best estimate of pressures of
vein formation. It has been argued that some high density CO2-rich fluid inclusions found in the KSZ were formed during peak metamorphism and thus document the presence of a CO2-rich fluid during peak granulite facies metamorphism (Rudnick et al. 1984). The association of high density CO2-rich fluid inclusions with clearly retrograde veins documents the formation of similar composition and density inclusions
after the peak of metamorphism. Thus, the coincidence of entrapment pressures calculated from fluid inclusion density measurements
with peak metamorphic pressures alone should not be considered strong evidence for peak metamorphic inclusion entrapment.
All fluid inclusion results are consistent with an initially semi-isobaric retrograde P–T path.
Received: 2 April 1996 / Accepted: 15 November 1996 相似文献
18.
Chemical composition of tourmaline from the Yunlong tin deposit, Yunnan, China: implications for ore genesis and mineral exploration 总被引：1，自引：0，他引：1
Summary ?The Yunlong tin deposit is located in the northern part of the Lancangjiang metamorphic zone of the Sanjiang Tethys orogen
series in western Yunan province of China. It consists of vein-type cassiterite ores, which are mainly hosted in migmatites
of Caledonian age. Abundant tourmaline is associated with the ores, quartz–tourmaline veins and barren migmatized gneiss and
migmatites. A detailed electron microprobe study has been carried out to document the chemical compositions of tourmaline
from this deposit. The results exhibit a systematic compositional change that might be used as tracer for ore genesis and
in prospecting for tin mineralization. Tourmalines from the ore bodies are dravite with Fe/(Fe + Mg) ratios of 0.09 ∼ 0.31
and Ca/(Ca + Na) ratios of 0.03 ∼ 0.40. These tourmalines are also rich in chromium (up to 0.74 wt% Cr2O3) and tin (up to 0.42 wt% Sn). In contrast, tourmalines from the barren migmatites are mostly schorl with Fe/(Fe + Mg) ratios
of 0.38 ∼ 0.94 and Ca/(Ca + Na) ratios of 0.00 ∼ 0.14. Tourmalines from quartz–tourmaline veins that occur between ore bodies
and the migmatites show intermediate compositions, i.e., Fe/(Fe + Mg) = 0.09 ∼ 0.59, Ca/(Ca + Na) = 0.01 ∼ 0.22.
It is suggested that the Mg-rich nature of the tourmaline can be used as an exploration tool in this region to target tin
mineralization, because the tourmalines show increasing Mg contents and are more dravitic when approaching the ore bodies.
It is likely that the formation of the Yunlong tin deposit was related to migmatitic-hydrothermal processes. The high Mg and
Cr contents in tourmalines from the ore bodies were probably derived from the local meta-sedimentary and meta-volcanic rocks
of the Precambian Chongshan Group rather than from the granites in the region.
Received December 28, 2000; revised version accepted January 25, 2002 相似文献
19.
Javier Sánchez-España Francisco Velasco Adrian J. Boyce Anthony E. Fallick 《Mineralium Deposita》2002,38(5):519-537
A fluid inclusion and stable isotopic study has been undertaken on some massive sulphide deposits (Aguas Teñidas Este, Concepción, San Miguel, San Telmo and Cueva de la Mora) located in the northern Iberian Pyrite Belt. The isotopic analyses were mainly performed on quartz, chlorite, carbonate and whole rock samples from the stockworks and altered footwall zones of the deposits, and also on some fluid inclusion waters. Homogenization temperatures of fluid inclusions in quartz mostly range from 120 to 280 °C. Salinity of most fluid inclusions ranges from 2 to 14 wt% NaCl equiv. A few cases with T h=80–110 °C and salinity of 16–24 wt% NaCl equiv., have been also recognized. In addition, fluid inclusions from the Soloviejo Mn–Fe-jaspers (160–190 °C and ˜6 wt% NaCl equiv.) and some Late to Post-Hercynian quartz veins (130–270 °C and ˜4 wt% NaCl equiv.) were also studied. Isotopic results indicate that fluids in equilibrium with measured quartz (d 18O fluid ˜–2 to 4‰), chlorites (d 18O fluid ˜8–14‰, dD fluid ˜–45 to –27‰), whole rocks (d 18O fluid ˜4–7‰, dD fluid ˜–15 to –10‰), and carbonates (d 18O ankerite ˜14.5–16‰, d 13C fluid =–11 to –5‰) evolved isotopically during the lifetime of the hydrothermal systems, following a waxing/waning cycle at different temperatures and water/rock ratios. The results (fluid inclusions, d 18O, dD and d 13C values) point to a highly evolved seawater, along with a variable (but significant) contribution of other fluid reservoirs such as magmatic and/or deep metamorphic waters, as the most probable sources for the ore-forming fluids. These fluids interacted with the underlying volcanic and sedimentary rocks during convective circulation through the upper crust. 相似文献
20.
M. Akaogi H. Takayama H. Kojitani H. Kawaji T. Atake 《Physics and Chemistry of Minerals》2007,34(3):169-183
The low-temperature isobaric heat capacities (C
p) of β- and γ-Mg2SiO4 were measured at the range of 1.8–304.7 K with a thermal relaxation method using the Physical Property Measurement System.
The obtained standard entropies (S°298) of β- and γ-Mg2SiO4 are 86.4 ± 0.4 and 82.7 ± 0.5 J/mol K, respectively. Enthalpies of transitions among α-, β- and γ-Mg2SiO4 were measured by high-temperature drop-solution calorimetry with gas-bubbling technique. The enthalpies of the α−β and β−γ
transitions at 298 K (ΔH°298) in Mg2SiO4 are 27.2 ± 3.6 and 12.9 ± 3.3 kJ/mol, respectively. Calculated α−β and β−γ transition boundaries were generally consistent
with those determined by high-pressure experiments within the errors. Combining the measured ΔH°298 and ΔS°298 with selected data of in situ X-ray diffraction experiments at high pressure, the ΔH°298 and ΔS°298 of the α−β and β−γ transitions were optimized. Calculation using the optimized data tightly constrained the α−β and β−γ transition
boundaries in the P, T space. The slope of α−β transition boundary is 3.1 MPa/K at 13.4 GPa and 1,400 K, and that of β−γ boundary 5.2 MPa/K at 18.7 GPa
and 1,600 K. The post-spinel transition boundary of γ-Mg2SiO4 to MgSiO3 perovskite plus MgO was also calculated, using the optimized data on γ-Mg2SiO4 and available enthalpy and entropy data on MgSiO3 perovskite and MgO. The calculated post-spinel boundary with a Clapeyron slope of −2.6 ± 0.2 MPa/K is located at pressure
consistent with the 660 km discontinuity, considering the error of the thermodynamic data. 相似文献