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Peter W. Lipman

Publications and source records attributed to Peter W. Lipman.

At least 55 records · Page 3Linked to original sources
USGS1989

South Arch volcanic field—Newly identified young lava flows on the sea floor south of the Hawaiian Ridge

Several young lava fields were imaged by GLORIA sidescan sonar along the Hawaiian Arch south of Hawaii. The largest, 35 by 50 km across, includes a central area characterized by high sonar backscatter and composed of several flow lobes radiating from a vent area. Reflection profiling and sea-floor photography indicate that the central lobes are flat sheet flows bounded by pillowed margins; thin surface sediment and thin palagonite rinds on lava surfaces suggest ages of 1-10 ka. Vents are localized along the arch crest near bases of Cretaceous seamounts. Two dredged flows are basanite and alkalic basalt, broadly similar to rejuvenated-stage and some pre-shield alkalic lavas on the Hawaiian Ridge. Arch volcanism represents peripheral leakage of melt from the Hawaiian hot spot over much larger areas than previously recognized. -Authors

Hawaiian Ridge↗
USGS1988

Voluminous submarine lava flows from Hawaiian volcanoes

The GLORIA long-range sonar imaging system has revealed fields of large lava flows in the Hawaiian Trough east and south of Hawaii in water as deep as 5.5 km. Flows in the most extensive field (110 km long) have erupted from the deep submarine segment of Kilauea's east rift zone. Other flows have been erupted from Loihi and Mauna Loa. This discovery confirms a suspicion, long held from subaerial studies, that voluminous submarine flows are erupted from Hawaiian volcanoes, and it supports an inference that summit calderas repeatedly collapse and fill at intervals of centuries to millenia owing to voluminous eruptions. These extensive flows differ greatly in form from pillow lavas found previously along shallower segments of the rift zones; therefore, revision of concepts of volcano stratigraphy and structure may be required.

Hawaii↗
USGS1980

Potassium-argon ages from the Mount Taylor Volcanic Field, New Mexico

Fourteen new K-Ar dates for volcanic rocks of the Mount Taylor field, New Mexico, indicate that most activity occurred between 4.3 and 1.5 m.y. (million years) ago. Peak activity was at about 3.0-2.5 m.y., both on the central andesite-rhyolite shield volcano and on the surrounding alkali basalt-trachyte volcanic plateau, and occurred concurrently with an episode of NNE-trending basin-range faulting. The K-Ar dates also indicate that the regional Ortiz pediment surface, graded to the ancestral Rio Grande, existed in the Mount Taylor area as recently as 3 m.y. ago and that 250-400 m of erosional downcutting has occurred in subsequent time. Growth of the Mount Taylor field was also concurrent with peak volcanic activity along the northeast-trending Springerville-Raton zone, a major late Cenozoic volcanic belt that is considered to reflect the presence of a regional structural discontinuity of Precambrian age in the North American craton.

New Mexico↗
USGS1979

Dynamics of the Continental Crust: suggestions for U.S. Geological Survey research in the 1980's

Crustal dynamics--the study of the movement of mass and energy within, into, and out of the Earth's crust--encompasses most efforts of earth science, either directly or as background and support. A new international program is being formulated to promote cooperative development of the concepts required to solve proliferating problems created by intensifying human use and misuse of the land and its resources. A tentative title suggested by the U.S. Geodynamics Committee for this program for the decade of the 1980's is "Crustal Dynamics: A Framework for Resources." The needs are pressing at both the national and international levels. Many reasons cited for undertaking this international program are akin to the justifications for forming, maintaining, or enlarging governmental geological surveys. Thus, the U.S. Geological Survey has an obligation to participate in the Crustal Dynamics Program to meet its expanding responsibilities to serve the nation effectively. A U.S. Geological Survey workshop was convened near Denver on September 20-23, 1978, to consider appropriate roles that might be played in the Crustal Dynamics decade. Some 60 Survey geologists, geophysicists, geochemists, and hydrologists participated. Principal questions addressed were: 1) What are the major earth-science problems that should be investigated during the next decade? 2) What are their implications to society? 3) What competence can be brought to bear on these problems and what further competence and tools need to be developed? 4) What roles are appropriate for the USGS within the broader national and international earth-science communities? This report presents some responses to these questions. Readers may recognize some defects. The report was prepared by several committees and its sections remain uneven despite editing. Insufficient time was available for either lengthy consideration or discussions, and no opportunity was provided for communication with colleagues in other organizations. The report is not a finished proposal for USGS participation in the Crustal Dynamics program, but rather is intended as a basis for further discussion and consideration both within the organization and with colleagues in other institutions and organizations, toward formulation of a viable program.

Open-File Report↗
USGS1978

Blue Ribbon Lineament, an east-trending structural zone within the Pioche mineral belt of southwestern Utah and eastern Nevada

The Blue Ribbon lineament is an east-west structural zone that is about 25 kilometers wide and passes through the Pioche mineral belt at about 38°10' N. It is best known in Utah, where it is at least 190 km long, and extends from the southern Sevier Plateau in the High Plateaus westward and across southern Mountain Home (Needle) Range in the Great Basin. It probably continues westward an additional 170 km into Nevada, where it connects with the eastern end of the 230-km Warm Springs lineament. The Blue Ribbon lineament is defined by range terminations and east-trending valleys, alinement of eruptive centers of middle Miocene (20 million years) to Pliocene(?) (5-1.8 m.y.) alkalic rhyolite, alinement of areas of middle Miocene to Pliocene mineralized rocks (mostly fluorine, uranium, tungsten) and hydrothermally altered rocks, east-trending magnetic highs and interruptions of magnetic anomalies, and east-striking basin-range faults of late Tertiary and Quaternary age. Mountains south of the lineament are topographically and structurally lower than those to the north. North-striking Quaternary basin-range faults, the Thermo hot springs area, several warm springs and former hot springs, and numerous dacitic to andesitic volcanic centers of early to middle Miocene age (26-20 m.y.) occur along the lineament. The Blue Ribbon lineament is believed to be a deep crustal fault zone dating from at least middle Miocene time and possibly much earlier. It thus developed generally coincident with northerly trending classical basin-range faults. Its fracture system was an important, long-lived conduit for mineralizing fluids, and it should be an attractive target for minerals exploration in the future. The lineament could be due to an east-trending warp in the subducting mantle plate, or it could be part of a past or present intracontinental transform fault that locally gets younger eastward and dies out eastward in the western Colorado Plateaus province.

Utah↗
USGS1976

Trace-element variations at Summer Coon volcano, San Juan Mountains, Colorado, and the origin of continental-interior andesite

The Oligocene Summer Coon center, an eroded continental-interior volcano of the eastern San Juan Mountains, Colorado, was the source of magmas ranging in composition from basaltic andesite to rhyolite. Previous Pb and Sr isotope studies indicate derivation of the magmas from an isotopically homogeneous source. This study presents new data for rare-earth elements (REE), U, Th, Ba, Sr, Rb, and Ni from 10 samples of the Summer Coon sequence. Alkali elements are high in all rocks; as SiO 2 increases, Ba increases from 900 to 2,000 ppm, Rb increases from 35 to 90 ppm, Sr decreases from 900 to 350 ppm, K/Rb decreases slightly, Ba/Sr increases, U increases from 0.5 to 2.5 ppm, and Th increases from 2 to 7 ppm. Chondrite-normalized REE patterns are strongly fractionated in comparison with oceanic-arc andesite-dacite sequences. La is 80 to 120 times chondritic abundance, but Yb and Lu are less than 10 times chondritic abundance. Small negative Eu anomalies characterize the rhyolites. Nickel in the andesites is 40 to 70 ppm. The origin of the andesite is interpreted in terms of nonmodal partial melting of a trace-element—enriched garnet-bearing source, possibly subducted crust that has converted to eclogite. Rhyodacite and rhyolite are interpreted as low-pressure crystal-fractionation products of silicic andesite, in which crystallizing phases are hornblende rich in REE and plagioclase.

Colorado↗
USGS1974

Palaeomagnetism and magnetic–polarity zonation in some Oligocene volcanic rocks of the San Juan Mountains, south–western Colorado

Palaeomagnetic results have been obtained from thirty sites in intrusive and extrusive rocks of Oligocene age from the San Juan Mountains, south-western Colorado. All specimens from each site were subjected to af demagnetization, and the reliability of each site determined. Twenty-three sites gave reliable results. Because five sites from the thick intracaldera part of the La Jara Canyon Member of the Treasure Mountain Tuff appear to have become magnetized during the same small interval of geological time, their results were combined and their mean pole and direction used in the final calculations. The eighteen remaining reliable sites yielded an average Oligocene palaeomagnetic pole at 85·6° N and 298·0° E (δ p = 8°, δ m = 11°, k = 24·1). A stratigraphic sequence is given for the major San Juan ash-flow sheets and selected additional units with their corresponding magnetic polarities and mean K-Ar ages.

Colorado↗
USGS1974

Relation of mineralization to calderas in the San Juan volcanic field, southwestern Colorado

A review of the calderas in the San Juan volcanic field, southwestern Colorado, indicates that lead, zinc, copper, gold, and silver mineralization took place in and near calderas which had complex histories of postsubsidence intrusive and extrusive igneous activity. Most known ore occurs in veins that follow fractures formed during the different caldera cycles, but some intrusive bodies were extensively mineralized and possibly may host disseminated, porphyry-type deposits. The mineral deposits seem to be related most commonly to the youngest and most highly differentiated late intrusives of a caldera cycle.

Colorado↗