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Kaersutite-series

Posted by Olav Revheim  
avatar Re: Kaersutite-series
May 22, 2011 04:18PM
    
Referring to literature it seems, that Kaersutite is not a rare mineral.
As far as information about occurrence and habit is available, it confirms what Olav wrote.

Sources:
(1) Deer, Howie, Zussman, (1997): Rock forming minerals, Double-chain silicates
(2) Leake, (1968): A Cataloge of analysed calciferous and subcalciferous amphiboles...
(cataloge of recalculated and renamed amphibole analyses that have been published post 1890)

The attached pdf´s give a selection and summary for locality, occurrence, and Ti-content.


Christof
Attachments:
open | download - Z 01.jpg (83.2 KB)
open | download - Z 02.jpg (45.4 KB)
Re: Kaersutite-series
May 22, 2011 08:35PM
    
Mandarino and Anderson ("Monteregian Treasures" Cambridge 1989) report two analyses for kaersutite from MSH with TiO2 of 5.65% (out of 98.74 total - wet chemistry by Chen) and 4.47% (out of 96.45 total - microprobe by Carleton University). (I don't know how to convert this to "afu" - but with Ti being one of 16 cations in the formula I would guess that a fully occupied site would require about 6.25%.)
Mandarino states that kaersutite is a rock forming mineral in sodalite syenite at MSH and that phenocrysts up to 4 cm long have been found. He also states that "The black, pitchy appearance [sometimes with red internal reflections] and its occurence as phenocrysts are distinctive for kaersutite."
Such material seems to be fairly common - though not much collected - at MSH.



Edited 5 time(s). Last edit at 05/22/2011 10:16PM by Modris Baum.
avatar Re: Kaersutite-series
May 22, 2011 11:10PM
    
This is special and usual feature of nonprofessional collector's thinking: "On this locality kaersutite is known. Kaersutite is amphibole. I should to found amphibole - it will be kaersutite." But nonprofessional collector very often unable even to recognize all amphiboles in locality and collecting only largest and well-crystallized of them.

I had observe this on very popular and famous in Soviet times Dashkesan deposit. In literature was described amphibole dashkesanite (chloro-potassichastingsite for the moment). Hundreds of collectors visited Dashkesan quarries every year, and almost every of them took cm-size specimen of "dashkesanite" from amphibole-bearing skarns (I was in their number). In reality this abundant on the locality amphibole was usual actinolite (listed in any guide of Dashkesan, by the way). And only many years later I obtain possibility to see real dashkesanite - it turn out quite different megascopicaly dark-coloured fine-granular material quite scarce on the deposit.
Many years gone, Dashkesan isn't so popular now, but in many "old" (40-30 years age) collections you able to found bluish-green "dashkesanite" masses with cm-long fibres. When you begin to explain situation, you receive answer - "It is from Dashkesan!" I am SEE, that it is from Dashkesan, but it is ACTINOLITE from Dashkesan!:X
And at least part of these collectors had walk over dashkesanite bearing skarns and hadn't will to pick up specimen with this ugly greenish-black fine-granular masses.

Story with kaersutite is the same, as I am suspect.
Kaersutite is small, microscopic mineral. It may present in masses of alkaline basalts as component of their matrix. But collectors always will collect at least large grains if they will unable to found large crystals.;)

I don't think, that making big pile from ALL known amphiboles is the best idea. But if you'll take 1000 hornblendes, for example, you'll fail 150-300 times. Within 1000 actinolites you'll found 980 of them. If you'll take 1000 kaersutites, you'll fail 955 times. If you'll take 1000 arfvedsonites from Khibiny, 650 of them turned out magnesio-arfvedsonites, 300 - aegirin-diopsides, may be 30-40 will be real arfvedsonites, and only 2-3 will turned out Magnesioferrikatophorite - [www.mindat.org] or riebeckites.

You should to understand, that most scientific publications are dedicated to more rare or "interesting" amphiboles. Only a few fanatics will write a special article about find once more locality of hastingsite or riebeckite. But I don't know any locality, where only a single amphibole was occur. 3-4-5 amphiboles on the same locality is more often situation.

When I'd prepare reports on mineralogy of Korean rare-metal deposits, I find two foolproof ways to increase mineral list of any locality:
A. to collect in field any amphibole from any new assemblage - 3-4-5 minerals for report are guaranteed
b. to collect any large segregations of sulphides - in one large grain galena or chalcopyrite you'll found microinclusions of 5-6 simple sulphides and native gold (silver, tin) in addition, if you are lucky.
As result the report looks comprehensive inspite of 2-3 amphiboles and 5-6 sulphides were stay out frame...
In any case, sometimes this way was very productive. For example, on Abdong deposit [www.mindat.org] ferroferrikatophorite-ferrorichterite amphibolites were empty as tram [www.mindat.org] while ferric-ferronyboite rocks were overfilled with ore minerals [www.mindat.org]
avatar Re: Kaersutite-series
May 22, 2011 11:16PM
    
Christof Schaefer Wrote:
-------------------------------------------------------
> Referring to literature it seems, that Kaersutite
> is not a rare mineral.

>:D<

Referring to literature ankerite also is not rare mineral. How much specimens of real ankerite with Fe>Mg had you hold in hands?;) :) :)
And parisie-(Ce) isn't too rare according to literature, but only 95 from every 100 parisites turned out bastnaesites or synchysites after checking.:X
Re: Kaersutite-series
May 22, 2011 11:17PM
Doelter (1914) has following kaersutite (linosite) analysis in % TiO2:
Kaersut (Lorenzen 1984): 6.75
Kaersut (Washington 1908): 10.25
Linosa (Washington 1908): 8.47

Milo
avatar Re: Kaersutite-series
May 22, 2011 11:23PM
    
TiO2 contents for kaersutite end member is 9.15 mas.% and 8 mas % for ferrokaersutite one. So them begin from 4.5 and 4 mas.% consequently.
[www.webmineral.com]
[www.webmineral.com]

So you, Modris, has good chances to become owner of best mineral specimen!;) If don't pick up wrong stone of course.



Edited 1 time(s). Last edit at 05/22/2011 11:24PM by Pavel Kartashov.
Re: Kaersutite-series
May 23, 2011 12:22AM
    
Hi Pavel,

One of the MSH analyses (TiO2 5.65%)) used wet chemistry. Wouldn't that suggest more than just microscopic zones (for MSH)?

Thanks - Modris

BTW This analysis had MgO 10.32% and FeO 11.97% The other one had MgO 12.78% and FeO 9.89%. These are both kaersutite- right?
Re: Kaersutite-series
May 23, 2011 08:33AM
    
Thank you all for contributing to a very interesting discussion both on the structure of the best of articles in general and kaersutite in particular. I'd like to add my understanding on kaersutite, which of course may be very much incorrect and any further contribution will be received with delight..

It appears that there is a general consensus amongst scientists that Ti rich ampibole ( Ti rich pargasite and kaersutite) play an important role in the upper mantle, and that these amphiboles can be stable in pressures up to 25-30kbar, and that these are in fact the amphibole in alkali-rich hydrous magmas, and it is even suggested that the melting of kaersutites may be one of the major sources for alkaline magmas:

"Specifically, we have observed the melting of kaersutite within ultramafic nodules from La Palma. Both the kaersutite and the glass produced through melting show strong compositional similarities to members of the alkali olivine basalt series. The observed relationships strongly indicate that alkali basalts may be derived from a melting event in which kaersutite is the principal participant."

Quote from:
W. C. FORBES & R. J. STARMER
Kaersutite is a possible source of alkali olivine basalts
Nature 250, 209 - 210 (19 July 1974)

Also other sources indicate that kaersutite is a common mineral in the upper mantle. However, the local conditions there is not favourable for mineral collectors.

-----

It does seem like kaersutite and Ti-rich pargasite is commonly brought to surface in undersaturated volcanic rocks, even as a rock-forming mineral:
" The mineral assemblage of Type I includes kaersutite (15-20 vol. %), feldspar (plagioclase = An33-An80, alkali feldspar = ~Ab55Or45), diopside (~Wo55En30Fs6), titanomagnetite (Ti# ~75), olivine (Fo48, Fo85) and apatite."

Quote from
Scanlan, Mary K.
Petrology of Inclusion-Rich Lavas at Minna Bluff, McMurdo Sound, Antarctica: Implications for Magma Origin, Differentiation, and Eruption Dynamics
2008

And there are many papers that present similar information.

-----

It also appears that Ti-rich amphiboles is not only found as a part of the groundmass of these volcanic rocks, but also as larger, crystalline grains:

"Kaersutitic amphiboles (Ti-rich varieties of hornblende) occur mainly in mantle-derived xenoliths associated
with alkalic lavas. Chemical and textural studies of natural samples, combined with experimental studies
of the stability of Ti-rich amphibole, have led to the consensus that poikilitic, vein, and megacrystic kaersutites
most likely are near-liquidus phases that crystallized over a range of high pressures,presumably under mantle conditions."
Quote from:
Robert K. Popp, David Virgo, Michael W. Phillips: "H deficiency in kaersutitic amphiboles: Experimental verification": American Mineralogist, Volume 80, pages 1347-1350, 1995

In fact it seems that Ti-rich amphiboles is rather common as megacrysts, and a google search for "kaersutite megacryst" gives more than 1000 hits. (Definition megacryst: Applied to the texture of any igneous or metamorphic rock which contains large, usually euhedral crystals set in a finer-grained groundmass. The term has no genetic connotation, unlike ‘phenocryst’ which implies crystallization from a magma, and ‘porphyroblast’ which implies solid-state recrystallization during metamorphism.
A Dictionary of Earth Sciences | 1999 | AILSA ALLABY and MICHAEL ALLABY, encyclopedia.com)

-----

But in a fine grained volcanic rock, will a megacryst generate anything bigger than a mm sized crystal in an even finer groundmass? That is hard to say. The kaersutite megacrysts from Minna Bluff, Antarctica is rarely larger than 1mm (M.K.Scanlan, 2008). The different papers do not often give a size for these megacrysts and most of them may well be smaller than what we as mineral collectors want them to be.

The following definition given by Braga at al ( European Journal of Mineralogy, 18, 223-231) gives mineral collectors some hope in that that collectable material might be found out there:

"Megacrysts are large (i.e. ≥ 1 cm) single and composite crystals that commonly occur in alkaline lavas together with mantle- and crust-derived xenoliths. They are generally interpreted as high-pressure phases formed from
the crystallization of magmas at upper mantle conditions, or as fragments of pegmatitic veins that crystallized from differentiated mafic magmas under a range of pressure and temperature conditions (Irving, 1974; Schulze, 1987; Shaw
& Eyzaguirre, 2000). Notwithstanding their origin, megacrysts represent valuable material to investigate the nature of melts and fluids infiltrating through the lithosphere."

Apparantly there are collectable material:

Yagi et. al. "Stability relations of kaersutite" University of Hakkaido publication 1975: describes rounded, well formed crystals up to 5cm ( Ti>0,5 apfu) in diameter from Kakanui, Japan, and as already written in the article, crystals up to 10-15cm are known from Vlčí Hora in the Czech republic. Multi-cm crystals are also known from Arizona and California in the US. I therefore find it likely that Ti rich amphiboles in the 1 cm range can be found at at least a few locations worldwide in alkali-rich volcanic rocks.

-----

The question remains how many of these ti-rich amphiboles that really are kaersuites with Ti>0,5 apfu. According to a table presented by Alberto Zanetti, the majority of analysed Ti rich amphiboles falls within a rather narrow window with an O/OH ration between 0,8 and 1,2 and a Ti content between 0,4 and 0,6 apfu. Exactly borderline between Ti-rich pargasite and kaersutite. Based on his data, an actinolite like definition of kaersutite such as Ti= 0,35-0,7 apfu would cover most of the Ti rich amphiboles in basanites and other alkali-rocks.

Also Ti-rich amphiboles with a Ti content as low as 0,257 and 2,6 apfu are published as kaersutite ( Hawthorne and Grundy( 1973) Pechar et al. (1989)), giving indications that not all "kaersutite" really are kaersutite.

I therefore follow Pavel's argument that some (many?) "kaersutite" locations therefore contain no kaersutite at all, whereas others will have both pargasite ( Ti<0,5 apfu) and kaersutite ( Ti > 0,5 apfu). For the locations that contains multiple amphiboles (almost all that is),without analysing a representative selection of multiple samples.

This has however been done for some locations: Colville et.al ( 1991) publish analytical data for 14 kaersutite megacrysts from the Cima volcanic field in California with Ti contents ranging from 0.50 to 0.74 (average 0.65).

The question is, I guess, what to do with locations where kaersutite with Ti>0,5 apfu are known when it is likely that an unknown percentage that may be somewhere between 1 % and 99% of the amphiboles are Ti rich pargasites ( or other amphiboles) with Ti< 0,5 apfu.?

Olav



Edited 3 time(s). Last edit at 05/23/2011 09:20AM by Olav Revheim.
avatar Re: Kaersutite-series
May 23, 2011 09:09AM
Well, the upper mantle might not be favorable to mineral collectors but I have been a few places to get specimens which may have been marginally less favorable.

Rock Currier
Crystals not pistols.
Re: Kaersutite-series
May 23, 2011 09:23AM
    
I guess that some of the California and Arizona desert locations might be pretty close to upper mantle, except that there are probably no rattle snakes in the mantle.

B)

Olav
avatar Re: Kaersutite-series
May 23, 2011 10:19PM
    
Olav Revheim Wrote:
-------------------------------------------------------

> 1) Does anyone ( Pavel?) have analytical data from
> any of the listed locations suggesting that the
> "kaersutite" entries are not kaersutite?

Unfortunately I never have most perspective specimens of kaersutites for tests (Australian, Greenland and Arizona) listed here. I had check specimens from Priazovie (Khlebodarovskii quarry), Vlčí Hora, some north Italian localities and Tunis. The later were so not interesting and low quality hornblendes, that they long ago lay on a garbage dump. But I still preserve two specimens, which I am able to show here.

First of them is basaltic hornblende from Vlčí Hora, received by me from Pavel Uher in 1991. I don't know from which type rocks (basanite , trachybasalt , basaltic trachyandesite, trachyte, rhyolite, nephelinite or tephrite) this crystal was extracted, but it is quite similar to photos of Marek Patúš, presented in the article.

Its size is ~4x1 cm. In its composition TiO2 contents range from 0.72 to 3.37 mas.%. The most titanoan composition (shown here) give empirical formula: K0.34(Ca1.30Na0.69)1.99(Mg3.45Fe3+0.64Al0.57Ti0.34)5.00[(Si5.51Al2.49)8.00O22 ]O0.52.
0.34 is significantly less of 0.51 apfu of Ti necessary for kaersutite. In reality more than 0.51, because titanium content divide between kaersutite and ferrokaersutite end members, and at least one of them should to predominate over other individual amphibole end members. But this is too complex and dark matter for usual collectors.
And this crystal is indistinguishable megascopicaly from "kaersutites" xls of Marek Patúš given here.



Edited 1 time(s). Last edit at 05/23/2011 10:21PM by Pavel Kartashov.
Attachments:
open | download - Hornblende_001.jpg (205.6 KB)
open | download - Hornblende_002.jpg (201.3 KB)
open | download - HornblendeB_001.jpg (128 KB)
avatar Re: Kaersutite-series
May 24, 2011 12:33AM
    
The second specimen had come from kersantite dyke of Khlebodarovskii quarry in Priazovie. Kersutite was described here by G.K. Eremenko in 1968 and 1969 (DAN USSR, not USSR itself, but Ukrainian SSR) and listed in monograph "Mineralogy of Priazovie".
All investigated specimens of "kaersutite" from here turned out titanoan pargasites. 4x3 cm specimen from photo is part of more large xenocrystal from kersantite. Its empirical formula is (K0.49Na0.28)0.77(Ca1.56Na0.44)2.00(Mg2.34Fe3+1.49Al0.74Ti0.43)5.00[(Si5.72Al2.28)8.00O22 ](OH)1.57.

For me, the most perspective on kaersutite specimen here is crystal from Anakie Mt, of course if it will not turn out augite or aenigmatite. Material from Lukov u Bíliny, Korretsberg Mt, Rothenberg Mt and Mt Etna are too similar to Vlčí Hora basaltic hornblende. And specimens from Predazzo are too similar to titanoan pargasite from Khlebodarovka.
What about ferrokaersutite from Sintra Mt in Portugal, its colour is too light for kaersutite, and especially for ferrokaersutite. But for pargasite it is quite suitable.
Attachments:
open | download - Hornblende_004.jpg (170.8 KB)
open | download - Hornblende_005.jpg (102.7 KB)
open | download - HornblendeB_003.jpg (111.9 KB)
Re: Kaersutite-series
May 24, 2011 07:24AM
    
Pavel,

Thank you very much for this information. smileys with beer. I will add the information you have from the Czech locations. As can be seen from the text and the references some of the large amphibole specimens from there are kaersutite with Ti>0,5. I am investigating this further to try to find as much as possible for the "first draft version" of this article.

I have requested additional information from the uploader of the ferrokaersutite specimens from Sintra, Portugal and got the following reply from Rui Nunes:

" Hello,
The label says yes! The dealer was (now dead) a very credible man and had a strong knowledge of the portuguese mineralogy.
Best wishes
Rui "

I have no reason to doubt this information, but because of lack of analytical data, <i have taken out this entry.

I have also had some privat correspondence with Cristof Schaefer on the brown amphiboles from the Eifel district, and as the definite identification on these are still not published work in progress, I have also removed these from the article.

Olav
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