petrogenetic significance of trace elements in igneous quartz
DESCRIPTION
Petrogenetic significance of trace elements in igneous quartz. Rune B. Larsen Francois Jacamon Bjorn Eske Sorensen Norwegian University of Science and Technology. Trace elements in quartz High T-P granites Medium T granites Low T granitic pegmatites Hydrothermal systems. - PowerPoint PPT PresentationTRANSCRIPT
Petrogenetic significance of trace elements in igneous quartz
Rune B. LarsenFrancois JacamonBjorn Eske SorensenNorwegian University of Science and Technology
• Trace elements in quartz• High T-P granites• Medium T granites• Low T granitic pegmatites• Hydrothermal systems
Vintermøte 2006, Stavanger
Why and how study trace elements in igneous quartz ?
Common mineral in all granitic igneous systems
Normally present throughout the igneous evolution
Remarkably resistent to subsolidus alteration
Fingerprinting origin, igneous evolution and hydrothermal overprinting
Potential geothermometer
Economic applications, HPQ, future SoG-Si rawmaterials
LA-HR-ICP-MS or EMPA
Quartz in dry granitic melts, high T, high P
T: 850 falling to 625 C
P: 7 to 5 kb
850 oC
640 oC
Quartz in wet granitic melts, medium T low P
Pegmatitic melts, low T, low P, wet and weird !
Primary Qz
Early Secondary Qz
Late Secondary Qz
0.1
10
11
00
10
00
0 . 1 1 1 0 1 0 0
E r z g e b ir g e , G r a n i t e ( 4 )
K le iv a n G r a n i t e
K r u s n é H o r y , G r a n i t e ( 3 )
K r u s n é H o r y
G r a n i t i c P e g m a t i t e ( 3 )
I - T y p e G r a n i t e
M e t a l u m i n o u s
S o r A - T y p e G r a n i t e
P e r a l u m i n o u s
W o r l d I g n e o u s Q u a r t z
N = 5 1 7
1) Jung L 2) Watt RG, Wright P, Galloway S. & McLean C 3) Müller A, Kronz A & Brieter K 4) Müller A, Weidenbeck M, van den Kerkhof A, Kronz A & Simon K
(1992)(1997)
(2002)(2002)
During the igneous evolution of granitic melts Ti in quartz is falling whereas Ge in quartz is going up. There are exceptions to this principles, however, the Ge/Ti ratio is strongly temperarure dependent.
Peraluminous granites, form qz with high Al contents. Evolved metaluminous granitic qz is low in this element. Alkaline granite comprise quartz with high K concentrations.
Largely, the quartz composition is buffered by the melt composition i.e is sensitive to melt origin, fractional crystallization, events of replenishment and the exsolution of an aqueous phase.
When infiltrated by aqueous fluids, Li, B, Al, Na, (K) and Fe are always remobilised whereas Ti, Ge and P normally are immobile. However, if inflitrated by high salinity alkaline fluids Ti, Ge and P are also mobilised
Qz is very robust during subsolidus weathering and may largely preserve the igneous fingerprint where other major minerals are decomposed.
Accordingly, qz partially preserve the igneous history and distinguish magmatic events in complex igneous terrains
Granitic pegmatite, particularly metaluminous and hydrothermally infiltrated GP’s are promising targets for HPQ prospecting