Ralph,
I would expect that the Cr6+ as in crocoite represents formation
from soluble Cr6+ in highly oxidized solutions. Those are not
typical of hard rocks however.
eric
On Jan 22, 2007, at 8:00 PM, Ralph Bottrill wrote:
> Ed
> In Dundas, Tasmania, there seems to be remarkably extensive Cr
> mobility
> from the original chromite (in serpentines) into stichtite (Mg-Cr
> carbonate) veins (+/- Cr-chlorites, magnetites, etc) and fuchsite
> along
> fault contacts, during metamorphism. Then, during weathering, much of
> this Cr was remobilised into the groundwaters and locally deposits in
> quite large masses of crocoite (lead chromate) and other secondary Cr
> (III and IV) minerals.
>
> regards
> Ralph Bottrill
> Mineral Resources Tasmania
> 03 6233 8359
>
> -----Original Message-----
> From: Metamorphic Studies Group [mailto:GEO-
> [log in to unmask]]
> On Behalf Of Eric J Essene 1
> Sent: Tuesday, 23 January 2007 08:15
> To: [log in to unmask]
> Subject: chromium mobility?
>
>
> Ed,
> One sometimes sees violet "kammererite" (chromian chlorite)
> flakes in country rocks near serpentinites, suggesting the mobility
> of Cr during serpentinization over scales of 10's of meters. The
> "fuchsite" (chromian muscovite) that is seen commonly in Archean
> metasediments probably forms primarily from nearby detrital chromite,
> but also indicates some mobility of Cr.
> eric
>
>
> On Jan 22, 2007, at 2:27 PM, Edward Grew wrote:
>
>> Chromium is normally considered immobile in metamorphic
>> environments. Has Cr mobility
>> been reported in either natural or experimental systems?
>>
>> Thanks!
>>
>> Ed
>>
>>
>
>
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