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‫שפע ימים בע"מ‬
‫)"החברה"(‬
‫ב"ה‪,‬‬
‫ה' בניסן תשע"ה‬
‫‪ 25‬במרץ ‪2015‬‬
‫לכבוד‬
‫רשות ניירות ערך‬
‫ירושלים‬
‫מספרנו )לשימוש פנימי(‪ :‬ט‪101/55947/‬‬
‫לכבוד‬
‫הבורסה לניירות ערך בתל‪-‬אביב בע"מ‬
‫תל‪-‬אביב‬
‫ג‪.‬א‪.‬נ‪,.‬‬
‫הנדון‪ :‬דוח מיידי‬
‫שפע ימים בע"מ )להלן‪" :‬החברה"( מתכבדת בזאת לצרף שלושה פוסטרים )גיליונות( שיוצגו במסגרת כנס של‬
‫החברה הגיאולוגית )המתקיים השנה במלון כינר שלחופה הצפון מזרחי של הכנרת‪ ,‬בתאריכים ‪.(24-26.3.15‬‬
‫יוער בהקשר זה‪ ,‬כי מידי שנה מציגה החברה בכנס החברה הגיאולוגית את ממצאיה האחרונים‪ ,‬לרבות‬
‫התקדמותה בתהליכי האקספלורציה שבמסגרת תחום פעילותה‪.‬‬
‫השנה יוצגו ‪ 2‬פוסטרים נוספים המתארים את ממצאי מחקרים שנערכו על ידי שני חוקרים חיצוניים לחברה‪,‬‬
‫אשר זכו לשיתוף פעולה מצד החברה‪ ,‬לאחר שגילו התעניינות גדולה בממצאי החברה ובשטחי ההיתרים בהם היא‬
‫פועלת‪ ,‬ובעיקר המינרל הטבעי והנדיר "מויסאנייט" שנמצא על ידי החברה‬
‫‪ 3‬הפוסטרים מציגים הן את התיחום של המרבץ האלובייאלי באורך של ‪ 4.5‬ק"מ שזוהה במקטע התיכון‬
‫)‪ (Mid Reach‬בקישון‪ ,‬הן ניתוח תוצאות מינרלוגיות של חבילת המינרלים החשובים היקרים בעיקר קורונדום‬
‫)ספיר ורובי‪ ,‬כולל המגוון לתעשייה( והקשר האפשרי למינרל הטבעי הנדיר מסוג מויסאנייט‪ ,‬והן את המינרלים‬
‫האינדיקטוריים לקימברליט )‪ (KIMs‬שמצביעים על עומק של כ‪ 100-‬ק"מ ויותר בגוף הראשוני )‪(Primary source‬‬
‫רקפת באגן ההיקוות של הקישון – ושלושת הפוסטרים גם יחד מהווים מיקשה אחת המאששת את הנחות‬
‫העבודה וממצאיה של החברה – כדלהלן‪:‬‬
‫פוסטר מס' ‪ - 1‬נושא הכותרת‪:‬‬
‫‪A TRANSIENT FLUVIAL PLACER IN THE MID REACH OF THE KISHON‬‬
‫‪) VALLEY, NORTHERN ISRAEL: INITIAL RESULTS OF FOLLOW-UP EXPLORATION‬תרגום‪ :‬מרבץ נחלי‬
‫נגיש במקטע התיכון של נחל הקישון ‪ -‬תוצאות ראשוניות של אקספלורציה ביעד ראשון(‪:‬‬
‫המודל הגיאולוגי האזורי של שפע ימים משנת ‪ 2014‬סייע בהגדרתו של מרבץ מינרלים כבדים נגיש‬
‫)‪ (heavy mineral alluvial placer‬באורך של כ‪ 4.5-‬ק"מ באזור ספציפי שבמקטע התיכון של נחל הקישון ע"י‬
‫שימוש בשיטות אקספלורציה בינ"ל‪ .‬על בסיס התוצאות‪ ,‬החברה מפתחת מודל גיאולוגי תלת‪-‬מימדי )‪ (3D‬מקומי‬
‫של המרבץ הנגיש בכדי לנתח ולהגדיר את פוטנצייאל המרבץ‪ ,‬בהתמקד בחבילת אבני החן היקרות ‪DMC suite -‬‬
‫)יהלום‪ ,‬מויסאנייט‪ ,‬קורונדום = ספיר ורובי( ובחבילת המינרלים הכבדים לתעשייה ‪-‬‬
‫‪Heavy Industrial‬‬
‫‪) Minerals-HIM suite‬קורונדום לתעשייה‪ ,‬זירקון‪ ,‬רוטייל‪ ,‬אילמינייט וגרנט( ‪ -‬שנמצאו בעבודות האקספלורציה‬
‫שביצעה החברה באזור ספציפי זה‪.‬‬
‫‪-2-‬‬
‫פוסטר מס' ‪ - 2‬נושא הכותרת‪High Pressure Indicator Minerals from the Rakefet Magmatic Complex :‬‬
‫‪) (RMC), Mt. Carmel, Israel‬תרגום‪ :‬מינרלים אינדיקטוריים בלחץ גבוה מהגוף המגמתי רקפת‬
‫)‪RMC-‬‬
‫‪ (Rakefet Magmatic Complex‬בהר הכרמל(‪.‬‬
‫אחד המקורות הראשיים למינרלים כבדים במקטע התיכון של נחל הקישון הוא הגוף המגמתי של רקפת‬
‫)‪ (Rakefet Magmatic Complex - RMC‬שעל הר הכרמל‪ .‬מחקר עדכני )‪ (2014-2015‬שנערך ע"י דייב )דוד( אפטר‪,‬‬
‫גיאולוג וגיאוכימאי דרום‪-‬אפריקאי עתיר ניסיון‪ ,‬שהתמקד במינרלים אינדיקטוריים לקימברליט )‪ (KIMs‬מה‪-‬‬
‫‪ RMC‬תחם את עומקי ההיווצרות של חלק ממינרלי ה‪ KIMs-‬הללו‪ .‬על אף שמרבית מינרלי ה‪ KIM-‬מצביעים על‬
‫מקור מעטפת עליונה )רדודה(‪ ,‬בעומק של כ‪ 100-‬ק"מ‪ ,‬רכיב אחד מתוך המאסף המינרולוגי מצביע על עומק גדול‬
‫אף יותר‪ ,‬מעל ‪ 100‬ק"מ‪ ,‬כזה המתקרב ל"חלון היהלום" ) ‪,(diamond window‬כלומר לטווח טמפרטורה ולחץ‬
‫גבוהים יותר המצוי בעומקים הידועים בעולם כשדות יציבות להתגבשות מינרלים אלו‪ ,‬בכללם יהלומים ‪.‬‬
‫הממצאים הראשונים של מחקר זה פורסמו בפוסטר שהוצג לראשונה במתכונת שונה בכנס החברה הגיאולוגית‬
‫בדרום אפריקה ‪ GSSA‬שהתקיים בחודש ספטמבר ‪ 2014‬בקימברלי דרום אפריקה‪.‬‬
‫פוסטר מספר ‪ – 3‬נושא הכותרת‪Corundum, Moissanite and Super-Reducing Conditions in the Upper :‬‬
‫)‪) Mantle Beneath the Lower (southern) Galilee (Israel‬תרגום‪ :‬תנאי גיבוש ייחודיים של קורונדום‬
‫ומויאסנייט ‪ -‬שמקורם בתנאים מחזרים )מדוללי חמצן( בכיסי המעטפת‪ ,‬מתחת לקרום כדור הארץ( ‪:‬‬
‫כיוון שהמינרל "קורונדום" הוא המינרל השכיח ביותר שאותר במרבץ האלוביאלי של המקטע התיכון של נחל‬
‫הקישון‪ ,‬נערך מחקר מדעי אודות מינרל זה שנדגם מכמה מקורות ראשוניים בהר הכרמל‪ ,‬שמתנהל ע"י פרופ' ביל‬
‫גריפין‪ ,‬מומחה בעל שם עולמי בגיאולוגיה של מעטפת כדור הארץ מאוניברסיטת ‪ ,Macquarie‬אוסטרליה בשיתוף‬
‫עם החברה‪ .‬מחקר זה )‪ (2014-2015‬מתמקד בהתגבשות הקורונדום ‪ -‬שמופיע בשתי גירסאות‪ :‬במופעי אבנים‬
‫יקרות )ספיר ורובי( או במופע שאינו מוכר כאבן יקרה )‪ - (NGC=Non-Gem Corundum‬ובקשר הסביר שלו‬
‫למינרל הטבעי והנדיר מויסאנייט )‪ (SiC‬ולתוצאות מחר זה תשובה באשר לשאלות מפתח לגבי הגיאולוגיה של‬
‫"כדור הארץ העמוק"‪.‬‬
‫יובהר בהקשר זה‪ ,‬כי‪) :‬א( פרופ' גריפין ודייב )דוד( אפטר אינם יועצים של החברה ואינם מועסקים על ידה; )ב(‬
‫אמנם החברה שיתפה עמם פעולה בדרך של מתן גישה לממצאיה‪ ,‬אך המסקנות המוצגות בפוסטרים שלעיל‬
‫הינן של פרופ' גריפין ודייב אפטר‪ ,‬לפי העניין‪ ,‬המבוססות על עבודתם העצמאית ומשקפות את דעתם בלבד; ו‪-‬‬
‫)ג( אין במסקנות החוקרים כדי להעיד על קיומן של אבני חן בעלי בכמות מסחרית בשטחי ההיתרים בהם‬
‫פועלת החברה‬
‫בכבוד רב‪,‬‬
‫שפע ימים בע"מ‬
‫נחתם ביום ה' בניסן תשע"ה‪ 25 ,‬במרץ ‪2015‬‬
‫על ידי אברהם טאוב )מנכ"ל ודירקטור( ועו"ד נתן דרוקמן )מזכיר החברה(‪.‬‬
A TRANSIENT FLUVIAL PLACER IN THE MID REACH OF THE KISHON VALLEY, NORTHERN ISRAEL:
INITIAL RESULTS OF FOLLOW-UP EXPLORATION
V. Toledo (1), J.D. Ward (2), M. de Wit (2), R. S. Spaggiari (3), H. Coopersmith (4), R.Wald (1)
(1) Shefa Yamim (A.T.M.) Ltd., Israel (2) Majimba Geo-Consulting cc, South Africa. (3) C&K Mining Incorporation, Cameroon (4) Consultant in Economic Geology, Colorado, USA
March, 2015
B"H
Shefa Yamim has developed a “source to sink” geological model (sensu Bluck et al., 2005; Toledo et al., 2014) to guide their exploration campaign for gem and heavy industrial minerals in both primary volcanic occurrences and secondary alluvial deposits
within the Kishon catchment of northern Israel. The gem minerals are diamond (D), moissanite (M) and the corundum varieties (C) of sapphire and ruby (the so-called DMC suite), with the heavy industrial minerals comprising non-gem corundum, zircon, rutile,
ilmenite and garnet (so-called HIM suite). This geological model highlights the structurally-confined, narrow Mid Reach of the Kishon Valley, between Tel Kashish and Jalame Junction, as a high-priority alluvial target accessible for follow-up exploration.
We report here the initial findings from the follow-up exploration in which mapping, drilling (134 drill holes) and trenching (24 excavations) methods were, and still are being, used. Results are captured in ArcGIS and gravel volumes are estimated from 3-D
reconstructions using Voxler® 3, Strater® 4 and Surfer®12 software. To date, the main findings are:The Kishon Mid Reach trunk stream deposits, preserved in low-lying terraces flanking the modern river, constitute a 4.5 km long
transient fluvial placer (sensu bluck et al., 2005) with mineralization confined to the basal, carbonate-dominated, cobbleboulder sized gravels some 0.5-4 m thick.
All basal gravels treated from drill intersections (total of 313 m) and trench samples (1,888 tonnes) have returned, to some
degree, positive results for the DMC and HIM suites. Sapphire is the most abundant DMC mineral, whilst non-gem corundum
the most common HIM mineral.
The alluvial fans derived from Mount Carmel are instrumental in forming the Kishon Mid Reach transient fluvial placer by:• Supplying boulder to cobble, oversize clasts into the Kishon trunk stream, thereby generating a coarse framework conducive
for trapping smaller but heavier placer minerals (sensu Ward et al., 1993; Jacob, et al., 1999).
• Infilling the left flank of the Kishon Valley below Mount Carmel, thereby forcing the Kishon trunk stream into a confined, and
hence more energetic, course along the right flank of the Mid Reach.
• Introducing the DMC and HIM suite minerals from primary volcanic sources in Mount Carmel into the Kishon Mid Reach placer
gravels.
The footwall of the Kishon Mid Reach placer comprises incompetent marls and carbonates that does not promote the formation
of fixed trapsites (sensu Jacob et al., 1999) and thus heavy mineral concentration is associated with semi-mobile gravel bar
trapsites.
The follow-up exploration phase will continue until the Kishon transient fluvial placer has been defined spatially and sampled
sufficiently to determine at least an Inferred Mineral Resource (sensu SAMREC Code, 2009).
Preliminary 3D modelling of the right bank (97 drillings)
Shefa Yamim Kishon Gap (Mid reach) datasets plan view
Geological cross section - right (east) bank.
Note the suspected normal fault
Geological cross section - right (east) bank
Geological oblique section across the Kishon river
A
Schematic 3D model of the Kishon Gap
References:
• Bluck, B.J., Ward, J.D. and de Wit, M.J.C., 2005. Diamond mega-placers: southern Africa
and the Kaapvaal Craton in a global context. In: McDonald, L., Boyce, A.J., Butler, I.B.,
Herrington, R.J. and Polya, D.A. (Eds). Mineral deposits and earth evolution. Geological
Society, London, Special Publications, vol. 248, 231-245.
• Jacob, R.J., Bluck, B.J. and Ward, J.D., 1999. Tertiary-age diamondiferous fluvial deposits of
the Lower Orange River valley, southwestern Africa. Economic Geology, vol. 94, 749-758.
• Toledo, V., Ward, J., De Wit, M., Spaggiari, R., and Coopersmith, H., 2014. Developing a
geological model to guide placer exploration in the Kishon Catchment, Northern Israel.
Abstract and poster presentation, Israel Geological Society, Annual Meeting, February,
2014.
• Ward et al., 1993
• WARD, J.D., BARKER, R. & CORBETT, I.B. 1993. Diamondiferous trapsites in Tertiary fluviatile
deposits of the Lower Orange River: preliminary observations., Conference on Mining
Investment in Namibia, 17-19 March 1993. Ministry of Mines and Energy, Windhoek,
Namibia, 20-21.
Recovery and Analysis of DMC Suite
HIM
Suite
Non gem Corundum
Garnet
Ilmenite
Rutile
zircon
B”H
March, 2015
High Pressure Indicator Minerals from
the Rakefet Magmatic Complex, Mt. Carmel, Israel.
D.B. Apter (1), V. Toledo (2), J.D. Ward (3)
(1) Dapter Delivers, South Africa (2) Shefa Yamim (A.T.M.) Ltd., Israel
(3) Majimba Geo-Consulting cc, South Africa.
The RMC occurs on Mt Carmel in N Israel: the geological setting, close to the Dead Sea Transform, has been previously well described (Sass,1980). The complex is one of a cluster of volcanic diatremes known in the area. Drilling in the Kishon valley by
Shefa Yamim (SY) identified a number of diamonds. Extensive exploration sampling by SY showed the area hosts abundant kimberlite indicator minerals. These indicators led, initially, to several specific vents within the RMC (Toledo et al 2010). A rock
sample from this locality ("Hill 66") was further found to contain a microdiamond, as well as indicator minerals. Considering such a tectonic setting is not normally associated with primary diamond deposits, it is of interest that this locality may be
diamondiferous. To this end a study of the mineral chemistry of the indicator minerals was undertaken to provide information about the host volcanic petrology and the nature of the upper mantle. The petrography of the volcanic host has been described as
kimberlite, alkali-tuffite, and according to EMW Skinner (2011) as 'something in-between' . We appear to be confronted with a suite of mafic to ultra-mafic components representing diatremes sampling xenoliths/xenocrysts from different levels in the upper
mantle and lower crust (Mittlefehldt, 1986).
Ilmenite
Upper Mantle Indicator Minerals from Rakefet samples
Chromite
Garnet
paragenesis
Eclogite
Lherzolite
Indicator Minerals and Mineral Chemistry
The classic kimberlite indicator mineral suite comprises unique chemical varieties of garnet, clinopyroxene, ilmenite, and spinel/chromite in the size range 0.30-0.425-0.71-1.00 mm. The SEMQ electron microprobe analyses of these minerals are presented here as major element oxide
weight percentages in a variety of scatter plots commonly used for kimberlite and diamond exploration.
The garnet compositions show two major populations: peridotitic-lherzolite (lhz) and eclogitic (ecl). These are classified G-varieties according to Grutter et. al. (2004). No sub-calcic (G10) garnets occur; lhz varieties (G9) have low Cr2O3 values (<<2wt%) and consistent Mg#'s (~0.84)
typical of the shallow mantle; the predominant garnet is eclogitic G3/G4 types. The classic Cr2O3 * Ca0 diagram (two variations: by TiO2, Mg#) applicable to peridotitic garnets, show isobars with a highest 'minimum pressure (Pmin38)' of 20.2kb suggesting derivation from at least
~60Km; a calcium projection of 4-5 wt% CaO also indicating a shallow mantle origin for the peridotitic garnets (Grutter et. al. 2006). The TiO2 * Na2O diagram is used for ecl garnets as a pressure proxy: some grains have Na2O values >0.07wt%, maximum Na2O ~0.12wt%, indicative
of potential diamond stability field pressures (Grutter and Quadling 1999).
The spinel (chromite) diagram (Cr2O3 * MgO by TiO2) is indicative of a shallow upper mantle peridotite source. However, the diagnostic kimberlitic high TiO2 population is not seen (Grutter and Apter 1998) and suggests no interaction between source magma and the lherzolite implying
magma depths from below the peridotite.
The lherzolitic clinopyroxene (cpx) compositions are given as Na * Ca + Al (per 6 oxygens) with plot variations for TiO2 and Mg#: fields for spinel and garnet peridotite are shown; Mt Carmel is consistent with both. Lhz cpx thermobarometry was computed using the technique of Nimis
& Taylor (2000) enhanced by integration with Nimis & Grutter (2010); a Temperature * Pressure/Depth plot is given. The cpx grains that qualify through stringent disequilibrium filtering show derivation from depths of ~75 to 110km at low temperature ~900degC: a single grain shows a
very low T of ~600degC. A model geotherm of ~45mW/m2 is estimated. By comparison, the Mt Carmel cpx are different to the off-craton margin Gibeon kimberlite cluster, Namibia, where rare diamonds are reported to have been recovered. The Gibeon cpx is from a slightly deeper but
much hotter lherzolitic upper mantle (Muatara 1998; Davies et. al. 2001). Cpx from a RSA diamond mine illustrate a cratonic kimberlite model where diamondiferous lhz occurs predominantly well below the graphite/diamond stability line on a ~40mW/m2 model geotherm (ie, typically
Kaapvaal craton; Gibson et. al. 2008).
Standard 'diamond exploration' ilmenite diagrams are presented. The TiO2 * MgO plot (with variations) is useful as a host rock paragenetic indicator (Wyatt et. al. 2004). These manganoan ilmenite (giekielite) show derivation from kimberlitic to para-kimberlitic sources and have typical
megacryst compositions wrt Cr2O3, Al2O3, and MgO.
In addition to recovery of the classic kimberlite indicators, abundant moissanite and corundum (sapphire and ruby) also occur in heavy mineral sample concentrates (4-6mm). Natural moissanite is predominantly restricted to mantle and meteorite origins. Kimberlitic moissanite from
diamondiferous sources (Shiryaev et. al. 2011) suggest moissanite grew at high temperatures and elevated pressures with formation of natural SiC by electrochemical processes in carbonate-silicate melts. Corundum also has a high pressure upper mantle origin as shown by kimberlite
borne corundum bearing eclogite xenoliths and unusual inclusions in diamond (Viljoen et. al. 1999).
Moissanite:
high pressure SiC.
Diamond
Sapphire
Ruby
Corundum
Moissanite
Ecl
Eclogite & Lhz Garnet
Lherzolite CPX
Lhz
CPX mineral compositions:
SP = Spinel peridotite
GP = Garnet peridotite
Garnet mineral compositions:
Lhz garnet minimum pressures: MaxPmin=20.2
Volcaniclastic Petrography:
1). K. Burger (De Beers Africa Exploration Laboratory): Kimberlite
2). Dr. Yudalevich Z. (Ben-Gurion University Beer-Sheva): Tuffite (AlkBasaltic)
Cratonic
Off-cratonic
3). EMW Skinner (Rhodes University, RSA):
Air-fall, pyroclastic, volcaniclastic glass with small macrocrysts and phenocrysts
of altered possible olivine, no other macrocrysts or phenocrysts are evident.
This rock is not a kimberlite, nor an alkali basalt.
Lherzolite CPX Thermobarometry:
Mt Carmel lherzolite (G9) CPX have a shallow , low
temperature origin. As compared to Gibeon (Namibia,
cratonic margin) and a typical South African diamond
mine.
Dia
Kimb
field
(Nimis &Taylor 2000 integrated with Nimis & Grutter 2009).
Adiabat
Kaapvaal
Craton
P'nC Geotherm models
Cratonic Kimberlite Cluster model.
Discussion and Conclusions
Diamond exploration indicator minerals from the Mt Carmel volcanics display the broad qualities of kimberlitic rock types. These occurrences are, by way of their setting, unusual and
therefore geologically significant. These rocks, in addition to containing typical kimberlite/upper-mantle indicator minerals (gar, spi, cpx, ilm) also contain considerable (and unusual)
concentrations of other high pressure minerals moissanite and corundum, as well as some diamond.
Kaapvaal
Craton
Upper Mantle thermobarometry: What can we expect from remote sensing?
The minerals are broadly grouped according to mantle derived peridotitic and eclogitic sources entrapped by, and related to the kimberlitic/volcanic event. The peridotitic lithosphere
is too shallow to be a source for any diamonds found. Using geothermobarometry, the peridotitic component indicates it does not intersect the diamond stability field. The eclogitic
component (predominantly gar, but also ilm/moi/cor (?)) cannot be compositionally used for PT estimations but suggest high pressures from Na-rich ecl-gars, other high pressure
minerals (moi, cor), and trace diamond. On face value these features imply an eclogitic source from at least deep enough to intersect the DSF some ~40km below the peridotite.
Diamonds (and moi, cor) recovered from these unusual rocks may derive from, possibly subducted, 'carbonated' eclogitic components of the lithosphere 'ponded/stacked' below the
peridotitic horizon and above the asthenosphere.
The Mt Carmel peridotitic indicators are consistent with peridotitic lithosphere depth characteristics estimated by Artemieva & Moodie (2001). A similar setting might also apply to the
unusual rare-diamond bearing volcanics found in Syria (Haggerty 1998) and the Luangwa rift valley in Zambia (Scott Smith, et. al.,1989).
Griffin, W.L., Gain, S.E.M., Toledo, V., Adams, D., O’Reilly, S.Y., Jacob, D.E., Pearson, N.J.
Shefa Yamim’s exploration for gem and heavy minerals in the Kishon and Zippori River catchments, on Mt Carmel and in the Menashe Hills of northern
Israel, has led to the discovery of an unusual association of xenocryst minerals in volcanic rocks and secondary alluvial deposits. This includes, inter
alia, diamond, zircon, rutile, ilmenite, garnet, corundum (gem-quality sapphire and ruby and non-gem corundum (NGC)) and the largest known
crystals (4.1 mm) of moissanite (SiC), a rare gem mineral. The relationships among these minerals are not yet clear; we report here initial findings on
the corundum species and their possible link to the moissanite in the primary occurrences.
Crystals of ruby and sapphire show weak cathodoluminescence (CL)
with some local oscillatory zoning; each grain appears to be a
single crystal. Ruby is characterized by high Cr2O3 but low Fe, Ti
and V. Sapphire, in contrast, is high in Fe, Mn, Ti and V, but low in
Cr. In these characteristics, the ruby and sapphire are similar to
corundum megacrysts found in alkali basalts in e.g. E. Australia,
Thailand and E. China.
< Binocular microscope images (scale bars are 1mm); a) gem quality ruby,
b) moissanite, c) various coloured, gem quality sapphires, d) NGC.
Ti Concentration in NGC
2.50
Weight % Ti
2.00
1.50
1.00
0.50
0.00
0
100
200
300
400
500
600
Distance (µm)
700
800
900
1000
1100
1200
Maps of cathodo-luminescence (CL) show that the NGC “megacrysts” are aggregates, with irregular melt pockets along
grain boundaries and inside the grains. EBSD (electron backscatter diffraction) analysis shows that the crystallographic C
axes of the larger crystals in each aggregate are parallel, but individual crystals are rotated around C relative to one
another. This suggests a type of parallel skeletal (harrisitic, or hopper) growth under supersaturated conditions.
CL
Bright CL correlates with low Ti, whereas the highest Ti contents completely extinguish the
CL. Ti contents increase linearly toward the melt pockets, suggesting a growth zoning rather
than inward diffusion of Ti. Stoichiometry implies the substitution of Ti3+ in the corundum. The
darkest CL is found in irregular “plumes” of very high Ti content (2-2.5% Ti) extending out of
melt pockets between grains or within grains, often up the cores of individual corundum
crystals. EBSD shows that these “plumes of high-Ti3+ corundum are slightly misoriented with
respect to the surrounding corundum. This pattern may be related to skeletal growth of the
large crystals and infilling of cavities by growth from the high-Ti residual fluids.
Ti-Al-Zr-Oxide
Al2O3
Ti2O3
Mg Spinel
Glass
^ Maps of BSE, CL and EBSD response across a corundum crystal; a) BSE image
with melt pockets internally and along grain boundaries, b) CL image with the
darker responses corresponding to higher Ti concentrations, which extend from
the melt pockets, c) EBSD image showing two different corundum orientations
and d) the high-Ti corundum (blue) is slightly misaligned relative to the host
grain, suggesting later infilling of skeletal cavities in the grains
Inclusions such as TiC and native V in the
NGC indicate extremely low fO2, >8 log units
below the Iron-Wustite (IW) buffer, commonly
accepted as the defining the minimum fO2 in
the upper mantle. Temperatures estimated
from the melt-pocket mineral assemblages
are in the range 1000-1400 °C; at present
there are no firm constraints on pressure.
> a) Calculated log(ƒO2) (normalized to FMQ buffer) for
xenoliths from the cratonic lithosphere; b) log(ƒO2) vs
pressure at 1773K of SiC assemblages and different
metal-metal oxide buffers. EMOG/D = EnstatiteMagnesite-Olivine-Graphite/Diamond buffer.
Ti-N
The melt pockets contain an unusual mineral
assemblage including inter alia Ti nitrides,
native Fe, V and Si, TiC, Fe-Ti-silicides and a
range of Mg-Al-Ti-Zr oxides and silicates. Many
of these phases sit in a matrix that appears to
be a glass dominated by Ca-Al-Si-Mg oxides.
None of the silicate or oxide phases contain Fe,
which is only present as the reduced metal. At
least two immiscible melts appear to have been
present, one a mafic silicate melt and the other
an Fe-Ti-Si-N melt.
< Typical inter/intra-granular melt pocket; spinel, Ti2O3
and a Ti-Al-Zr oxide have crystallized from the melt, now a
glass. Ti nitrides may have crystallized from a separate
melt.
Summary
The fO2 levels defined by the inclusions in the melt pockets of the NGC are low
enough to stabilize moissanite (SiC), and suggest a genetic link between the SiC
and the reduced melts trapped within the NGC, although SiC has not been
observed in melt pockets. The NCG aggregates may represent a type of harrisitic
(skeletal) growth of corundum from a substrate, trapping the melts from which
they were crystallising. The presence of glass suggests that crystallization was
ongoing when the xenocrysts were entrained in the rising magmas. The processes
that have generated the super-reducing conditions in these melts remain unclear.
The Mt Carmel mineral associations thus hold the keys to some important
petrological problems, and will provide many new insights into the upper mantle.