Shao-Yong
There are a couple of problems with adularia:
1. it is strictly meant to refer only to a rhombohedral form of low-T
K-feldspar, which commonly, but not always, exhibits a high-T structural
state
2. Most recent studies on potassic alteration in and about felsic
plutons and ore bodies described only "K-feldspar" or "orthoclase" and
little data is available on its nature.
A lot of epithermal deposits contain adularia: see Economic geology Reviews
No. 2, etc.
Deer Howie & Zussman have considerable data and references for adularia,
mostly in veins.
I do not know of any adularia or Ba-rich adularia associated with
massive
sulfide deposits but celsian occurs at the Rosebery and Broken Hill massive
Pb-Zn deposits, Australia. There are K-feldspar-rich sediments at the Mt Isa
Pb-Zn deposits, but the nature of these is uncertain.
I hope this helps.
-----Original Message-----
From: [log in to unmask] [SMTP:[log in to unmask]]
Sent: Saturday, 26 February 2000 22:22
To: [log in to unmask]
Subject: Re: Sanidine in plutonic rocks??
Dear Ralph Bottrill and Piergiorgio Rossetti,
I am interested in the occurrence of adularia in magmatic rocks and
related
hydrothermal veins, as you pointed out. Are there any publications
related
to this topic?
It seems to me adularia (and in particular Ba-rich adularia) is a
low-temperature hydrothermal mineral, usually associated with
massive
sulfide deposits.
Cheers,
Shao-Yong
*********************************
Prof. Shao-Yong JIANG
Department of Earth Sciences
Nanjing University
Nanjing 210093
P.R. China
Phone & fax: +86 25 359 4746
Email: [log in to unmask]
***********************************
-----Original Message-----
???: Piergiorgio Rossetti <[log in to unmask]>
???: [log in to unmask]
<[log in to unmask]>
??: 2000?2?16? 16:55
??: Re: Sanidine in plutonic rocks??
In my experience, also adularia can be almost uniaxial. In Oligocene
magmatic stocks from the Italian Western Alps, adularia occurs both
as
euhedral crystals within hydrothermal veins and as replacement
product after
magmatic K-feldspar and in part plagioclase.
Best regards
Piergiorgio
----------------------------------------------------
Piergiorgio Rossetti
Dipartimento di Scienze Mineralogiche e Petrologiche
Universit?di Torino
via Valperga Caluso, 35
10125 Torino, Italy
Tel.: +39 011 6707107
Fax: +39 011 6707128
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